IC-2 - 10th International Conference
Science and Engineering of Novel Superconductors

Session IC-2.A Structure, dimensionality, physical chemistry and general properties

IC-2.A:IL01  Rectification of Electronic Noise in Multilayers from Manganite Perovskites and Cuprate High-Tc Superconductors
C. BERNHARD, Department of Physics, University of Fribourg, Fribourg, Switzerland

I will show that YBa2Cu3O7/Nd0.65(Ca0.7Sr0.3)0.35MnO3 ((YBCO/NCSMO) heterostructures exhibit a rather large spontaneous voltage (SpV) effect that is caused by electronic noise rectification and allows one to drive a persistent current across an external circuit. The underlying ratchet-type electronic potential originates from a complex domain state within the NCSMO layers which involves various nearly degenerate electronic and magnetic orders. In particular, the competition between a ferromagnetic (FM) minority phase and a charge/orbital ordered majority phase with polar moments and charged domain walls appears to be essential. An important role is also played by the thin YBCO layers that only partially screen the electric field emanating from the NCSMO layers and thus enable an activated lateral charge transport that is non-reciprocal. Our findings highlight that cuprate/manganite multilayers can be used for efficient energy harvesting.


IC-2.A:IL03  Disorder in FeSe1−xSx (0 ≤ x ≤ 1) Superconducting Crystals
C. PETROVIC, Shanghai Advanced Research in Physical Sciences, Shanghai, P.R. China

Connections among crystal chemistry, disorder and critical temperature Tc are at the forefront of superconductivity. In Fe-based superconductors Tc correlates with the average anion height above the Fe plane. By synthesizing FeSe1−xSx (0 ≤ x ≤ 1) single crystal alloys with atomic defects we find that their Tc is not correlated with the anion height. Instead, changes in Tc(x) and tetragonal-to-orthorombic (nematic) transition Ts(x) on cooling are correlated with Bragg plane and Fe vibrations disorder in direction orthogonal to Fe planes and thereby induced scattering rates (1/τ)(x). The disorder stems from deformed Fe(Se,S)4 tetrahedra with different Fe-Se and Fe-S bond distances. Moreover, high-temperature metallic resistivity in the region of strong disorder exceeds Mott limit and is an example of the violation of Matthiesen’s rule and Mooij law which is known to be a dominant when adding moderate disorder past the Drude/Matthiassen’s regime in all materials. Scattering mechanism of Mott limit-exceeding resistivity arises from strong Se/S atom disorder in tetrahedral surrounding of Fe. Observations point to intricate connection between nanostructure details and unconventional scattering mechanism, possibly related to charge-nematic or magnetic spin fluctuations.


IC-2.A:IL04  Two-gap Superconductivity Induced by Gate-driven Hydrogen Intercalation in the Charge-density-wave Compound 1T-TiSe2
E. PIATTI, G. GAVELLO, G.A. UMMARINO, R.S. GONNELLI, D. DAGHERO, Department of Applied Science and Technology, Politecnico di Torino, Torino, Italy; C. TRESCA, G. PROFETA, Department of Physical and Chemical Sciences, University of L’Aquila, L’Aquila, Italy; G. PRANDO, P. CARRETTA, Dipartimento di Fisica, Università di Pavia, Pavia, Italy; F. KOSUTH, P. SZABÒ, P. SAMUELY, Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovakia

Transition metal dichalcogenides feature rich phase diagrams often including superconducting (SC) and charge-density wave (CDW) orders. Among them, 1T-TiSe2 has been one of the most extensively investigated. The pristine compound is not SC but features a commensurate CDW phase below 200 K, which is suppressed – in favor of the emergence of a SC dome with critical temperatures up to 4.15 K – by intercalation with various elements and molecules, applied pressure, and electric-field induced charge doping. The structure of the SC order parameter and its interplay with CDW order are still debated and seem not to be universal in the doped, intercalated, and pressurized systems. In this Talk, I will present clear evidence for a two-gap SC phase in the recently-discovered H-intercalated TiSe2 compound revealed by directional point-contact Andreev-reflection spectroscopy and scanning tunneling spectroscopy measurements down to 0.3K, by the temperature-dependence of the upper critical magnetic field, and their combined quantitative analysis within the two-band BCS and Eliashberg theory. The two-gap structure may arise from an extremely anisotropic distribution of the SC gap function on the single Fermi surface of the material due to the orbital-selective filling induced by H intercalation.


IC-2.A:IL05  Quest for High-temperature Superconductivity and Novel States of Matter in MXenes and Complex Oxide Heterostructures
A. GOZAR^1,2,3, I. BESPALOV^3,4, J. ZHAO^3,5, R. WU^3,5,6, I. BOZOVIC^3,8, ¹Department of Physics, Fairfield University, Fairfield, CT, USA; ²Department of Physics, Yale University, New Haven, CT, USA; ³Energy Sciences Institute, Yale University, West Haven, CT, USA; ⁴Department of Applied Physics and Materials Science, Caltech, Pasadena, USA; ⁵Department of Physics, Emory University, Atlanta, GA, USA; ⁶State Key Lab, Chinese Academy of Sciences, Beijing, China; ⁷Center of Material Science, Univ. of Chinese Academy of Sciences, Beijing, China; ⁸Shanghai Advanced Research in Physical Sciences, Pudong, Shanghai, China

Novel states of matter with exceptional properties such as superconductivity at high temperature, strange metal transport, nematic, density-wave or topological electronic  states  are hallmarks of interest in today’s condensed matter physics. We have used a dual approach to investigate these problems: by synthesis and characterization of atomically thin metallic layers of light elements and by studying interface effects in artificial copper oxides heterostructures. Borophene, a crystalline monolayer sheet of boron, is envisaged to play a unique role in the materials-by-design paradigm due to its extraordinarily rich polymorphism. On the other hand, interfaces in complex oxides may display enhanced properties than either of their single-phase constituents. We have used a unique ultra-high vacuum system for synthesis, by Molecular Beam Epitaxy, and in-situ characterization, by Low Energy Electron Microscopy, of micron-size borophene crystals on Cu(111) and Cu(100) substrates. Our real-time imaging capabilities provide information about the growth of faceted borophene islands up full monolayer coverage and also about phase-stability, evaporation and sub-surface dissolution. Combining low energy electron diffraction with scanning tunneling microscopy and ab initio theory allows us to resolve the crystal structures as triangular networks with vacancy ratios η = 1/5 for Cu(111) and η = 1/6 for Cu(100) surfaces. First-principles calculations indicate that charge transfer rather than covalent bonding, couples borophene to the underling Cu surfaces. The calculated electronic band structures host multiple anisotropic Dirac cones. We also employed atomic force microscopy (AFM) combined with scanning near-field optical microscopy (SNOM) for ex-situ characterization of borophene and ultra-thin oxide films. The AFM-SNOM signal is known to be resonantly enhanced by plasmonic or lattice excitations confined to interfaces. Using a customized set-up, we showed that it can visualize with a spatial resolution better than λ/3000 surface Josephson plasma waves in a high-temperature superconductor. We also demonstrated that AFM-SNOM is a quantitative tomographic tool for non-invasive 3D characterization of nano-scale devices and their fabrication techniques. Our data in borophene films reveal dielectric contrast between borophene and substrates showing that one can hope to use the unique capabilities of AFM-SNOM to access intrinsic properties and collective electronic excitations in metallic or potentially superconducting layers.


Session IC-2.B Properties of superconductors (of any type)

IC-2.B:IL06  Tunneling Study of Spin-triplet Proximity Effect in Cuprate/Manganite Thin-film Heterostructures
JOHN WEI, RAINNI CHEN, University of Toronto, Toronto, Canada; M. LAGOS, J. REYES-GONZALEZ, McMaster University, Canada

This Talk examines the in-plane cuprate/manganite proximity effect (PE) involved in the long-range Josephson effects that were recently reported in lateral cuprate/manganite/cuprate heterostructures. We focus on the superconductor/ferromagnet (S/F) PE along the [110]-axis, a crucial direction by virtue of the d-wave pairing symmetry and anisotropic band structure of cuprates. Scanning tunneling spectroscopy is used to probe manganite/cuprate thin-film bilayers, and the data is analyzed with PE theories that take full account of the frequency, spin and parity parts of the pairing symmetry. Our results have critical implications for the extremely long range (~ 1um) of the reported S/F/S Josephson phenomenon, which has been attributed to the generation of odd-frequency spin-triplet pairs at the cuprate/manganite interfaces and the propagation of these spin-triplet pairs through the half-metallic manganite spacer.


IC-2.B:IL07  Directional Andreev-reflection Spectroscopy of Sr2RuO4 : Constraints to the Order-parameter Symmetry
R.S. GONNELLI¹, R.K. KREMER², A. MACKENZIE³, A.S. GIBBS³, G.A. UMMARINO¹, Y. FUKAYA⁴, G. CSIRE⁵, M. CUOCO⁵, D. DAGHERO¹, ¹Department of Applied Science and Technology, Politecnico di Torino, Torino, Italy; ²Max-Planck Institute for Solid State Research, Stuttgart, Germany; ³University of St Andrews, St Andrews, Scotland, UK; ⁴Faculty of Environmental Life, Natural Science and Technology, Okayama University, Okayama, Japan; ⁵CNR-SPIN, and Dipartimento di Fisica “E.R. Caianiello”, Università di Salerno, Fisciano (Salerno), Italy

Thirty years after its discovery, the unconventional superconductivity of the layered strongly-correlated Sr2RuO4 with Tc = 1.5 K still presents several unclear aspects. In particular, the order parameter symmetry has been recently the subject of renewed, intense interest, but no experiment has so far definitively and unambiguously determined it. Here, we present the results of directional soft point-contact Andreev-reflection spectroscopy (DPCARS) down to 300 mK in very high-quality single crystals of Sr2RuO4. The crystals were cut along (100), (110) and (001) planes and we made the soft point contacts by placing a small drop of silver paste on these planes. The directional Andreev-reflection raw spectra reproducibly show a zero-bias conductance peak (ZBCP) for current injection along the [001] direction (c-axis contacts) and two-peak s-wave-like features for injection along the [100] and [110] directions (ab-plane contacts). We analyzed these results by two different theoretical methods applied to two promising inter-orbital pairing symmetries: the spin-singlet/orbital-singlet/odd-parity and the spin-triplet/orbital-singlet/even-parity one. The observed spectral features of our DPCARS curves are well reproduced by the spin-singlet inter-orbital odd-parity pairing.


IC-2.B:IL08  Exotic Pairing States in FeSe-based Superconductors
TAKASADA SHIBAUCHI, Department of Advanced Materials Science, University of Tokyo, Japan

Fe-chalcogenide superconductors exhibit intriguing properties, including nonmagnetic nematic order and its quantum critical points, possible time-reversal symmetry breaking (TRSB) in the superconducting state, and topological superconductivity. I will review recent progress in the studies of FeSe-based superconductors. In FeSe1-xSx superconductors, the nematic order can be completely suppressed at x=0.17, above which a possible ultranodal pairing state with Bogoliubov Fermi surfaces appears with a reduced critical temperature Tc. By using electron irradiation, we study the impurity effect in the unlranodal state, from which we find the lifting of gap nodes by disorder, suggesting that the Bogoliubov Fermi surfaces are susceptible to disruption by the disorder, as in the case of accidental nodes not protected by the pairing symmetry. In the Te substitution case, we find evidence for TRSB superconductivity in the bulk from zero-field muon spin relaxation measurements, which suggests that the topological superconductivity discussed in this system is a unique case of coexistence between TRSB superconductivity and a topologically nontrivial electronic structure.


IC-2.B:IL09  Field-dependent Electronic Specific Heat and Condensation Energy – Absence of Superfluid Density Loss in Overdoped Cuprates
J.L. TALLON, Robinson Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand

The current paradigm for overdoped cuprates is that the superfluid density (SFD), is progressively suppressed with continued overdoping. Such behavior is unconventional and suggests that the SFD is depleted either by pair-breaking or by the growing presence of a non-pairing channel, and moreover that phase fluctuations dominate the superconducting phase curve. Here we examine four measurables from the electronic specific heat of a number of overdoped cuprates including Y0.8Ca0.2Ba2Cu3O7-d, La2 xSrxCuO4, and Bi2Sr2CaCu2O8+d, and find that none of these support this current paradigm over the doping range considered. They are: (i) the specific heat jump, (ii) the residual specific heat coefficient at T=0, (iii) the zero-field condensation energy, and the field-dependent entropy shift. The only exception is Tl2Ba2CuO6+d which seems to be an outlier. The analysis thus far is model-free. However, it may be extended using the London model to quantify the SFD and it is found that this evolves hand-in-hand with the density of carriers per plaquette suggesting that all available carriers condense into a superfluid in which pair-breaking is absent. If confirmed this would imply a shift towards a more conventional view of overdoped cuprates in which phase fluctuations play only a minor role.


IC-2.B:IL10  Superconductivity in Novel Electride Materials
HECHANG LEI, Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, China; and Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China, Beijing, China

We report the superconducting properties of La3In and La3Al single crystals with Cu3Au structure. La3In and La3Al shows a superconducting transition at Tc ~ 9.3 K and 6.3 K. The Tc of La3In is much higher than element La (Tc ~ 6 K). Moreover, La3In shows a linear temperature dependence of resistivity in a wide range between 10 and 300 K, implying a non-Fermi liquid behavior of La3In. In contrast, the resistivity curve of La3Al shows a kink at ~ 55 K. Angle-resolved photoemission spectroscopy (ARPES) measurements reveal that La3In has a high density of states (DOS) which originates from the band near M point of Brillouin zone. Such high DOS could also explain the electron correlation feature of La3In. Interestingly, theoretical calculations also show that there are significant amount of anionic electron states in La3In and La3Al locating at the body center position, suggesting that La3In and La3Al may be electride superconductors. In this presentation, we will also introduce a new kind of superconductor with chiral crystallographic structure.


IC-2.B:L11  TiN/dielectric Nanolaminates: Effects of Metamaterial Engineering and Disorder on the Superconductive Properties
V.N. SMOLYANINOVA, S. POKHREL, T. SNARSKI, J. ARTEAGA, M.S. OSOFSKY, Towson University, Towson, MD, USA; A.C. LANG, V. WHEELER, J.C. PRESTIGIACOMO, Naval Research Laboratory, Washington, DC, USA

A series of TiN ultrathin films and TiN/dielectric nanolaminates were deposited using ALD to investigate whether the previously demonstrated metamaterial approach for enhancing the superconducting properties of layered (i.e., hyperbolic metamaterial) structures is applicable to TiN. While ultrathin TiN films become insulating at thicknesses of 4.5 nm and below due to disorder, metallic behavior and superconductivity are restored in the nanolaminates. In multilayers with layer thicknesses greater than 4.5 nm, the critical temperatures are enhanced compared to those of the single layer samples with the same thicknesses. The effects of disorder will be discussed. This study demonstrates that the metamaterial engineering approach for hyperbolic superconductors leads to a complex interplay between normal-state resistivity and the enhancement of the attractive electron–electron interaction, effectively improving their superconducting properties.
This work was supported in part by ONR Awards N000142312699 at Towson University and by ONR N0001425GI01664 at the Naval Research Laboratory.


Session IC-2.C Mechanisms (for normal and superconducting states)

IC-2.C:IL12  Coincidence of the Metal-insulator Transition and Epsilon near Zero Condition: Implications for Superconductive Tc Enhancement
V.N. SMOLYANINOVA¹, L. HAMANN¹, T. HANNESSON¹, S. POKHREL¹, J. FIELDS¹, J. NOUAL¹, D. ALIGHOLIZADEH², M. SAJINI DEVADAS², S.S. FIELDS³, S.P. BENNETT³, J.C. PRESTIGIACOMO³, M.S. OSOFSKY¹, ¹Department of Physics Astronomy and Geosciences, Towson University, Towson, MD, USA; ²Department of Chemistry, Towson University, Towson, MD, USA; ³Materials Science and Technology Division, Naval Research Laboratory, Washington, DC, USA

A study of the magnetic, electronic transport, and dielectric properties of a series of sputter grown amorphous FeCuB samples with varying metal/B content was performed to explore the relationship between the room temperature values of the dielectric function ε(ω) and distance to the disorder-driven metal-insulator transition (MIT). This relationship is relevant to observations that the superconductive transition temperatures (Tc) of many systems is enhanced near the MIT as well as other studies showing that Tc can be enhanced using metamaterial engineering where ε(ω) is negative and near zero (ENZ). The results demonstrate that, as expected, ε(ω) ~ 0 at metal concentrations similar to those near the MIT so that the ENZ condition is satisfied near the MIT on the metallic side. Furthermore, a composition near the MIT (and thus, satisfying the ENZ condition) was found that displayed signatures of superconductivity. These results imply that the enhancement of Tc in disordered superconductors is due to the presence of the ENZ condition which causes an enhancement of the attractive electron-electron interaction.


Session IC-2.D Vortex lattice physics

IC-2.D:IL13  Discovery of Higher Charge Superconductivity Beyond Charge-2e Cooper Pairs
JIAN WANG, International Center for Quantum Materials, School of Physics, Peking University, Beijing, China

Despite of the various forms of superconductivity, conventional or unconventional, topologically trivial or nontrivial, the condensation of charge-2e Cooper pairs with the quantized magnetic flux in units of h/2e has remained the origin and character of all superconductivity, as described by the BCS theory. We report our experimental discoveries of the charge-4e and charge-6e superconductivity in ultrathin ring devices fabricated using the kagome superconductor CsV3Sb5. These new phase coherent states are discovered by the observation of the quantized magnetic flux in units of h/4e and h/6e in systematic magneto-transport measurements. Our observations provide direct experimental evidence for the existence of phase coherent paired quantum matter with the duality of fractional quantum vortex state beyond the charge-2e superconductors, and provide ground work for exploring the physical properties of the charge-4e and charge-6e superconductivity as unprecedented phases of matter beyond the condensation of charge-2e Cooper pairs described by the BCS theory.


IC-2.D:IL14  Microwave Studies of Vortex Dynamics and Vortex Pinning in Low-Tc and High-Tc Superconductors
G. GHIGO, M. FRACASSO, R. GERBALDO, L. GOZZELINO, Politecnico di Torino - DISAT, Italy and INFN Sez. Torino, Italy; C. PIRA, INFN - Laboratori Nazionali di Legnaro, Italy

We report on vortex dynamics and pinning properties of superconductors, investigated for both fundamental and application-oriented purposes by means of microwave coplanar waveguide resonator (CPWR) techniques, useful to characterize thin-films [1] and small single crystals [2]. Data analysis gives the London and Campbell penetration depths, complex impedance, and vortex-motion-induced complex resistivity [3,4]. The complete set of vortex-pinning parameters is discussed in the framework of high frequency vortex dynamics models. In this presentation, an overview is given of recent results obtained by means of the CPWR technique, concerning the effects of introducing controlled defects by ion irradiation in different systems, ranging from Nb-based to cuprate superconductors. Different ion beams were used, from 0.5-MeV protons to 1.2-GeV Pb ions, with the aim to investigate the role of the qualitatively different defects (as for dimensions and morphology) in modifying the vortex dynamics and pinning properties of low-Tc and high-Tc superconductors.
[1] Phys. Rev. B 71, 214522 (2005); [2] Phys. Rev. Lett. 121, 107001 (2018); [3] Sci. Rep. 13, 9315 (2023); [4] Superconductivity, 13,100149 (2025).
We acknowledge the partial support of INFN under the CSN5 experiment SuperMAD.


IC-2.D:IL15  Vortex Generation in Superconducting Skyrmion Heterostructures
C. PANAGOPOULOS, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore

Topological solitons and quantum mechanics have been intertwined for the past sixty years. Even before the term soliton had been coined, Abrikosov’s theory predicted the formation of vortices in the phase field of superconductors, an exemplary exposition of macroscopic quantum coherence. Recent work shows that solitons are in fact a timely and promising platform for quantum operations. I will demonstrate the viability of using spin topology to influence a superconductor at selective length scales through a completely new material architecture namely, a stack of magnets and a superconductor that shows stable vortices above elongated chiral spin textures, as well as isolated skyrmions [1]. This is an excellent geometry for fluxonics and chiral superconductivity, as well as quantum processes such as non-perturbative, non-contact Majorana braiding.
[1] A. Petrovic, C. Psaroudaki, P. Fischer, M. Garst, and C. Panagopoulos Colloquium: Rev. Mod. Phys. 97, 031001 (2025).


Session IC-2.E Synthesis and processing

IC-2.E:IL16  Kramers Nodal Lines, Weyl Fermions and Superconductivity in InxTaS2
E. MOROSAN, Rice University, Houston, TX, USA

Kramers nodal lines (KNLs) are a special type of Weyl line degeneracies that connect time reversal invariant momenta (TRIM). KNLs are robust to spin orbit coupling (SOC), and are inherent to all non-centrosymmetric achiral crystal structures. In this talk, I will present magneto-transport and ARPES experimental data together with DFT calculations, pointing to the existence of novel KNLs in SmAlSi. SmAlSi develops an incommensurate spin density wave order at low temperatures. I will show evidence for the symmetry-protected KNLs, as well as Weyl fermions in SmAlSi. I will then contrast the properties of SmAlSi with those of the intercalated transition metal dichalcogenides InxTaS2 (ITS). The ITS compounds showcase the cleanest FS with a single KNL crossing the Fermi level, and also feature superconducting ground states below Tc between 0.6 K and 2.5 K (when x = 1/2, 2/3 or 1). Our AQOs and ARPES data on InTaS2 point to the existence of pinch points enforced by KNL, reminiscent of 2D massless Dirac fermions on the surface of 3D topological insulators. So when the pinch points with (2n+1)*pi (n = integer) Berry curvature are gapped by superconductivity, they are expected to produce nontrivial vortex spectra hosting chiral Majorana zero modes.


IC-2.E:IL17  Superconducting Properties of Nickelate Superconductors under Hydrostatic Pressure
DI PENG, Shanghai Advanced Research in Physical Sciences, Shanghai, China

The discovery of high-temperature superconducting (HTS) materials has profoundly transcended the theoretical boundaries of conventional BCS theory, with their anomalous superconducting properties establishing an ideal platform for investigating the mechanisms of unconventional superconductivity. Recent advancements in nickelates have further expanded this research frontier, offering a novel experimental paradigm for unraveling HTS mechanisms. Nevertheless, critical gaps persist in our current understanding of nickelates materials, particularly regarding the systematic elucidation of pressure effects-pressure being a pivotal parameter governing electronic structure and lattice symmetry. Hydrostatic pressure, distinguished by its uniform stress distribution and minimal lattice distortion artifacts, enables a more authentic representation of intrinsic pressure-induced responses, thus serving as a critical bridge connecting ambient-condition physics with extreme-condition physics. By integrating high-pressure diffraction, high-pressure electrical transport, and high-pressure magnetic measurements under isostatic pressure, we systematically investigate the structural evolution and superconducting properties of bilayer and trilayer nickelate superconductors under high-pressure conditions. Based on these experimental results, we construct a phase diagram encompassing structural, density-wave, and superconducting states across pressure-temperature space, elucidate the pressure-induced competition and transition mechanisms among superconducting phases, and thereby establish a universal phase diagram model to advance the fundamental understanding of nickelate superconductors. 


Session IC-2.F Power applications

IC-2.F:IL18  Tunneling Spectroscopy Studies of Niobium for the Development of SRF Cavities and Superconducting Qubits
J.F. ZASADZINSKI, S. RICE, Illinois Institute of Technology, Chicago, USA; M. IAVARONE, JUNKI MAKITA, Temple University, Philadelphia, PA, USA; F. CRISA, M. BAL, A. MURTHY, A. GRASSELLINO, Superconducting Quantum Materials and Systems Center, Fermilab, Batavia, USA

There is now considerable evidence for paramagnetic moments in the surface oxides of Nb originating in oxygen vacancies (Nb4+) that lead to unpaired electron spins. It is of high interest to elucidate how such paramagnetic moments might influence the Nb surface superconductivity in SRF cavities as well as provide possible two-level-system (TLS) and non-TLS RF loss channels relevant for qubit performance. Here we summarize a large set of tunneling spectroscopy studies including point-contact (PCT) measurements utilizing the native Nb oxide as well as vacuum scanning tunneling microscopy/spectroscopy (STM/STS) of backsputtered bare Nb and of capped Nb surfaces. A rich array of spin-flip Kondo physics has been observed including well-defined, sub-gap Shiba states in the superconducting phase of Nb due to coupling to the nanoscale paramagnetic surface sub-oxides. In some cases there exist quasiparticle states near zero bias that could couple to RF fields and produce Ohmic non-TLS losses. Such non-equilibrium quasiparticle losses would impact SRF cavity Q values and offer decay channels for Nb based qubits. A distinct Kondo tunneling channel is also observed that produces a pronounced zero-bias conductance peak.


IC-2.F:IL19  Irradiation Effects in Superconductors for Nuclear Fusion
A. BODENSEHER, M. ASIYABAN, M. EISTERER, Atominstitut, TU Wien, Vienna, Austria

Nuclear fusion of deuterium and tritium in a magnetically confined plasma is a promising candidate for the future generation of electric energy. This fusion reaction produces a neutron that is needed to produce tritium for a sustainable fuel cycle. However, a small fraction of the neutrons will reach the magnets that enclose the fusion plasma and introduce defects in the superconductor. Current concepts for fusion magnets are based either on REBCO or Nb3Sn. High-fluence neutron irradiation of these two materials was performed in a TRIGA research reactor to investigate the resulting degradation of the superconducting transition temperature and critical currents. The results are compared and can be explained by the simultaneous introduction of efficient pinning centers and the increase of scattering that results in a decrease of superfluid density as predicted by conventional theories. Nb3Sn turns out to be less sensitive to radiation damage because non-magnetic scattering is not pair-breaking as in cuprate superconductors.


IC-2.F:IL20  Current Transport, Energy and Health Applications of High-Tc Superconductors
J. STOREY, Robinson Research Institute and MacDiarmid Institute, Victoria University of Wellington, Wellington, New Zealand

The advent of high-temperature superconductivity, nearly 40 years ago, was accompanied by much hope and hype that they would revolutionize society through lossless energy transmission, super-efficient machines, and levitated trains. Progress was inevitably slowed by science and engineering challenges posed by these intriguing materials, but significant advances have been made. To meet global sustainability goals, the promised benefits of high-temperature superconductors are needed now more than ever. At Robinson Research Institute, numerous projects are underway to raise the technology readiness levels of high-temperature superconducting machines in the areas of electric aviation, space, energy, and health. This presentation will showcase some of this work with emphasis on barriers we are addressing to accelerate uptake of this technology.


IC-2.F:IL21  Superconductors for Future Colliders
A. BALLARINO, CERN, European Organization for Nuclear Research, Geneva, Switzerland

Superconductivity is a key enabling technology for high-energy particle accelerators. Nb-Ti has long been the workhorse superconductor for existing colliders, offering exceptional reliability, manufacturability, and cost effectiveness. However, achieving higher beam energies, increased luminosity, and improved long-term sustainability necessitates a transition to advanced superconductors capable of generating higher magnetic fields, potentially with reduced cryogenic demands. This contribution reviews the requirements, recent advances, and long-term perspectives for next-generation accelerator magnets, with a focus on superconducting materials—including Nb₃Sn, high temperature superconductors (HTS) such as REBCO and Bi-2212, and emerging conductor architectures.


Session IC-2.G Low-power applications and superconducting electronics

IC-2.G:IL22  Low-loss Materials for 2D Transmons with Lifetimes and Coherence Times Exceeding 1 Millisecond
N. DE LEON, Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, USA

Building large, useful quantum systems based on transmon qubits will require significant improvements in qubit relaxation and coherence times. Most efforts aimed at improving coherence have focused on avoiding loss and decoherence through novel qubit designs, which require radically new processor architectures and gate schemes. By contrast, materials improvements are a powerful approach to reducing loss and decoherence in superconducting qubits because such improvements can be readily translated to large scale processors. We recently demonstrated 2D transmon qubits that have both lifetimes and coherence times exceeding 0.3 milliseconds by using tantalum as the material in the capacitor. We then parametrized the remaining sources of loss using systematic measurements of the dependence of loss on temperature, power, and geometry. This playbook allows for rational, directed improvement of superconducting qubits, which we have used to realize 2D transmons with coherence times exceeding 1 millisecond and lifetimes up to 1.68 milliseconds. Because we have improved the underlying material system without alteration to the qubit architecture, these qubits are readily translated to existing control schemes, and we demonstrate single qubit gates with 99.994% fidelity.


IC-2.G:IL23  Reentrant Superconductivity and Superconductor-to-insulator Transition in a Naturally Occurring Josephson Junction Array Tuned by RF Power
S. AVRAHAM, S. SANKAR, S. SANDIK, A. BURSHTEIN, M. GOLDSTEIN, E. SELA, Y. DAGAN, School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel

Superconductivity usually vanishes when magnetic field\temperature (T) is high. Rarely, it reappears with increasing field\T: reentrant superconductivity, often linked to competing orders in correlated materials. Here we demonstrate reentrant superconductivity as a function of both T and magnetic field, tuned by RF power in a relatively simple system: granular aluminum, a naturally occurring Josephson junction (JJ) array. At low T, giant Shapiro steps emerge, exhibiting characteristics of a single JJ. Coherent phase locking across the array’s multiple junctions amplifies the quantized voltage, enabling tunability at radio frequencies, as observed in artificially designed JJ arrays. We show that our system can be tuned from a coherent superconducting to an insulating state using RF power. We propose that the RF power modulates the Josephson coupling energy. At elevated temperatures, the screening of the electron charge suppresses the charging energy, causing superconductivity to reappear. This many-body effect cannot be described within a single junction framework and involves correlations. Our system can therefore be tuned to observe both the single-junction regime and many-body correlation effects, serving as a quantum simulator for complex phenomena in condensed matter physics.


Session IC-2.H Topological Superconductivity & Spin-Orbit Effects

IC-2.H:IL25  Physics and Applications of Andreev Spin Qubits
V. FATEMI, Cornell University, Ithaca, NY, USA

Superconducting qubits and semiconducting qubits are two leading solid-state platforms for quantum computation, each coming with distinct strengths and challenges. Hybrid structures made of both semiconductors and superconductors aim to combine the best features of both platforms. One such hybrid structure is the Andreev spin qubit, which hosts a microscopic, fermionic spin degree of freedom inside a Josephson weak link. The key feature is the spin-dependent supercurrent – this physics enables long-range, quantum coherent interactions between spins despite their microscopic size, offering new architectural opportunities based on this hybrid system. In this talk, I will first present an introduction to Andreev spin qubits and what is unique in relation to both quantum dot spin qubits and superconducting qubits. I will then describe a new insight as to how we can use Kramers’ theorem to our advantage for designing error-correction modules, followed by our recent experiments developing the hardware to better understand coherence of Andreev spins hosted in InAs nanowires. Finally, I will conclude with key future challenges and opportunities for this platform.


IC-2.H:IL26  Emergent Interfacial Superconductivity in Hybrid Magnetic/Topological Heterostructures
N. SAMARTH, Pennsylvania State University, University Park, PA, USA

The synthesis of complex epitaxial quantum materials allows the exploration of emergent phenomena arising from broken symmetry, spin-orbit coupling, and topology. We focus on emergent superconductivity in van der Waals (vdW) heterostructures that interface magnetism and topology. In FeTe/(Bi,Sb,Cr)2Te3, we discuss the surprising concurrence of superconductivity, ferromagnetism, and topological insulator surface states [1]. We then extend this approach to show emergent superconductivity and non-reciprocal transport in FeTe/ZrTe2/CrTe2 heterostructures that interface a Dirac semimetal with a 2D ferromagnet [2[. These epitaxial heterostructures provide attractive wafer-scale vdW platforms for exploring unconventional superconductivity in topological quantum materials and for developing non-reciprocal devices for superconducting electronics.
Supported by the Penn State 2DCC-MIP (NSF Grant No. DMR-2039351) and the Penn State Center for Nanoscale Science/MRSEC (NSF Grant No. DMR-2011839).
1. H. Yi et al., “Interface-induced superconductivity in magnetic topological insulators,” Science 383, 634-639 (2024); 2. S. Islam et al., “Emergent superconductivity and non-reciprocal transport in a van der Waals Dirac semimetal/antiferromagnet heterostructure,” arXiv: 2504.20393.


Session IC-2.I Superconductivity in two-dimensional and layered materials

IC-2.I:IL27  Emergent Magnetism and Novel Electronic Phases in Transition Metal Oxide Heterostructures
M. RADOVIC, Photon Science Division, Paul Scherrer Institut, Villigen PSI, Switzerland

Transition metal oxides (TMOs) host a rich variety of emergent electronic and magnetic phases arising from the strong interplay between spin, orbital, charge, and lattice degrees of freedom. In ultrathin layers, these interactions can be tuned enabling the design of heterostructures where entirely new states of matter emerge. In the first part of the talk, I will discuss the LaNiO₃/LaTiO₃ superlattice, where interfacial electron transfer induces a high-spin configuration on Ni sites, stabilizing macroscopic magnetic order. Using Muon Spin Rotation, X-ray Absorption Spectroscopy, and Resonant Inelastic X-ray Scattering, we directly identify a quasi-two-dimensional antiferromagnetic state with relevance for spintronic functionalities and connections to precursor phases of cuprates and nickelates. The second example focuses on ultrathin NdNiO₃ (NNO) interfaced with ferromagnetic La₂/₃Sr₁/₃MnO₃ (LSMO). X-ray magnetic circular dichroism, Angle Resolved Photoemission Spectroscopy (ARPES), and first-principles calculations reveal a direct interfacial magnetic exchange that drives an unexpected ferromagnetic phase in NNO, suppressing its native antiferromagnetic insulating ground state. Together, these results demonstrate that interfacial engineering of magnetic interactions provides a powerful route to realizing electronic and magnetic phases that are absent in the corresponding bulk materials. The work highlights TMOs as a versatile platform for controlling correlated quantum states and advancing next-generation quantum and spintronic devices.


IC-2.I:L28  Disordered Superconductivity in Layered Graphene Oxide - Transition Metal Nanocomposite System
S. MUKHOPADHYAY¹, R. YANG¹, K. WHEELER¹, J. PRESTIGIACOMO², M. KOOLEL-VEETIL², M. OSOFSKY³, L. PFEFFERLE¹, ¹Yale University, New Haven, CT, USA; ²Naval Research Lab, Washington DC, USA; ³Towson University, MD, USA

The emergence of superconductivity in a Moire based graphene system commonly attributed to flat bands has been one of the most exciting recent discoveries in correlated electron systems. The superconductivity in Moire systems is typically in the few hundred millikelvin range. We introduce a system consisting of transition metal (Palladium or Platinum) nanoparticles randomly intercalated in a regularly spaced graphene oxide bilayer. When exposed to a hydrogen source at high temperature (1000 C) and pressures around 5 GPa and brought back to ambient pressures these systems show superconductivity ranging from 1.5 to 5 K depending on the nanoparticle type and the pressure treatment. The superconducting transition is probed by using SQUID magnetometry, resistance and specific heat measurements. The randomly distributed nanoparticles are about 5 nm in diameter but the correlation length from Hc2 measurements are around 200 nm which points to the significant role of the graphene oxide matrix. X-ray diffraction measurements at the Argonne National Lab and high resolution TEM measurements will be presented to elucidate the structural details and how it may help to understand the emergence of superconductivity in this highly disordered graphene oxide system.


IC-2.I:L29  Increase of Critical Current Density of GdBCO Coated Conductors and YBCO Films by Treatment Under High Pressure - High Temperature Oxygen Atmosphere
T. PRIKHNA^1,2,4, R. VLAD², A. KETHAMKUZHI², M. KARPETS^1,3, R. KLUGE⁴, B. BÜCHNER⁴, S. PONOMARYOV⁵, V. MOSHCHIL¹, X. OBRADORS², T. PUIG², ¹V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, Kyiv, Ukraine; ²Institut de Ciencia de Materials de Barcelona, CSIC, Campus UAB, Bellaterra, Spain; ³National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine; ⁴Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany; ⁵V.E. Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine

Coated conductors (CC) with thin (about 2 µm) superconducting REBCO (RE=Y, Gd, Eu, etc) layer, textured along c-axes, are considered to be the most promising high-temperature superconducting (SC) materials for different applications. The level of SC characteristics, critical current density, Jc, in particular, of CC to high extent depends on the oxygenation process which affects charge carriers’ density, nH, of REBCO layer. It was shown that some overdoping by oxygen of YBa2Cu3O7-δ (Y123) film (at 1 bar at low temperature) lead to Jc increase due to increase in nH. In the present study we oxygenated GdBCO_CC via Ag layer (repeatedly) and tetragonal Y123 film on singlecrystalline SrTiO3 substrate under 100-160 bar pressure at 600 and 800ºC. We observed signs of overdoping for GdBCO_CC (confirmed by the increase in nH, resistance behavior and decrease in the c-parameter), accompanied by an increase in Jc(77 K, 0 T) by 21.5% (from 2.12 to 2.70 MA/cm2). For the Y123 film (215 nm thick), saturated with oxygen at 100 bar, 600 ºC, 8 h, nH(100 K)=10.78×10 21 cm-3, and Jc increased by 61 and 71% compared to the values after standard oxygen saturation at 1 bar: Jc(77 K, 0 T)=3.74 MA/cm2, Jc(5 K, 0 T)=33.34 MA/cm2 versus Jc(77 K, 0 T)=2.28 MA/cm2, Jc(5 K, 0 T)=24.83 MA/cm2.


IC-2.I:IL30  Atomically Thin Superconductors as a Platform for Superconducting Quantum Circuits
JOEL I.-J. WANG, New York University, New York, NY, USA

Van der Waals (vdW) superconductors remain superconducting down to the monolayer limit, offering a platform to explore emergent phenomena and device functionalities arising from reduced dimensionality. Their ability to form atomically sharp heterostructures further enhances their potential for quantum devices. I will present the characterization of the kinetic inductance in atomically thin NbSe₂—a two-dimensional transition-metal dichalcogenide (TMD) superconductor—using superconducting coplanar waveguides and microwave techniques adapted from circuit quantum electrodynamics. The kinetic inductance scales inversely with layer number, reaching 1.2 nH per square in the monolayer limit, and exhibits a crossover from clean- to dirty-limit behavior as thickness decreases, driven by surface scattering, multiband superconductivity, and confinement. The measured self-Kerr nonlinearity (–0.008 to –14.7 Hz/photon) highlights the suitability of NbSe₂ for compact, nearly linear, high-inductance quantum devices. I will conclude by discussing the prospects of TMD superconductors as a materials platform for superconducting qubits and fully integrated quantum circuits.


IC-2.I:IL31  Phonons at YBa2Cu3O7 / LSAT Interfaces
J. REYES-GONZALEZ¹, CHAO ZHANG², R.K. CHEN², JOHN Y.T. WEI², M.J. LAGOS¹, ¹McMaster University, Department of Materials Science & Engineering, Hamilton, ON, Canada; ²University of Toronto, Department of Physics, Toronto, ON, Canada

Bulk and surface phonons are considered to play a role in the transition temperature Tc of superconductor thin films. Optical based techniques dominate phonon studies of thin films, but those methodologies offer limited information on interface contributions. This talk reports on an atom-scale spectroscopy study of phonon modes at YBa2Cu3O7/LSAT interfaces using electron energy loss spectroscopy (EELS) [1]. Epitaxial YBa2Cu3O7 thin films were grown on LSAT substrates by pulsed laser deposition, which was confirmed using scanning transmission electron microscopy and x-ray diffraction. Phonon modes were probed at different locations within the film and near the LSAT boundary with atomic resolution. Some of those modes are unequivocally to Y-123 layered units, while the other modes can be linked to mixed contributions from YBCO and LSAT [2]. Correlation between atomic structure and phonon properties unveil local interfacial modes that are active near the interface. Our findings can crucially inform ongoing theoretical debate on the role of electron phonon coupling in cuprates, by revealing how the coupling varies from the bulk to interfaces.
[1] M. J. Lagos, et al., Microscopy 71, i174 (2022); [2] J. Reyes-Gonzalez, et al., Phys. Rev. Mat. 9, 074801 (2025).


IC-2.I:IL32  Cuprate Twistronics Past and Future
N. POCCIA, University of Naples Federico II & IFW Leibniz Institute of Dresden, Italy - Germany

High-temperature superconducting complex oxides (La₂₋ₓSrₓCuO₄, YBa₂Cu₃O₇₋ₓ, Bi₂Sr₂CaCu₂O₈₊ₓ) are oxygen-rich and electronically heterogeneous, forming a landscape of “puddles.” The puddles intrinsic metastability makes them challenging to control in modern electronic systems. While early research focused mainly on their nitrogen-range critical temperatures (Tc), current interest increasingly targets their unique and still-mysterious electronic states. Nearly four decades of materials research have revealed both the limitations and the vast potential of these superconductors for emergent electronics — extending far beyond mere large-scale energy applications. To preserve the previously mentioned interfacial metastability, we exfoliate cuprate layers using cryogenic stacking technologies that have enabled a material science led revolution, starting an intense research activity on cuprate twistronics. This seminar reviews the key challenges in engineering these fragile materials for electronic integration and presents our solutions based on silicon nitride platforms. Finally, we discuss the opportunities these systems offer for photonic and qubit design if we balance control with scalability and energy optimization.