Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q57: Superconductivity: Hydrides & Other SC Materials -IIIRecordings Available
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Sponsoring Units: DCMP Chair: Peyman Azodi, Princeton University Room: Hyatt Regency Hotel -Clark |
Wednesday, March 16, 2022 3:00PM - 3:12PM |
Q57.00001: GeneralizedĪ·-pairing models and transition temperature in flat-band superconductors Aaron Chew, Jonah Herzog-Arbeitman, Andrei B Bernevig Certain flat band tight-binding models have exact η-pairing ground states in which superconductivity can be analytically studied. We generalize the η-pairing models to include generalized bipartite crystalline lattices [1], extending the flat-band superconducting models in [2] to realistic materials. Our formalism allows for an analytic calculation of charge +1 and +2 excitations above the ground state, the superfluid weight, and a perturbative calculation of the maximum transition temperature and the location of the van Hove singularity. We apply our results in the context of recent work performed in flat band superconductors such as twisted trilayer graphene [3], demonstrating the need for modifications to BCS theory in the presence of strong coupling. |
Wednesday, March 16, 2022 3:12PM - 3:24PM |
Q57.00002: Retention of high-pressure-induced superconducting and non-superconducting phases in high-temperature superconductors at ambient Paul C. W Chu, Liangzi Deng, Zheng Wu, Trevor Bontke, Shuyuan Huyan, Melissa J Gooch, Rabin Dahal, Bin Gao, Tong Chen, Pengcheng Dai, Yu Xie, Xue Li, Ketao Yin, Yanming Ma The search for high-temperature superconductivity (HTS) in hydrogen and hydrogen-rich compounds under high pressure has a long history. Recently, several reports (1-4) of high Tc up to 288 K in hydrides under pressure of up to 267 GPa have appeared. The ultrahigh pressure needed to create the HTS in hydrides has hampered the detailed study of the phenomenon, as well as any applications. To lower the required pressure, even to zero, we have developed a pressure-quench process (PQP) and have demonstrated it successfully in stabilizing at ambient the high-pressure-induced HTS phase and other phases in FeSe and Cu-doped FeSe (5). It is not inconceivable that the PQP may be adapted for hydrides with Tc approaching room temperature. The results will be presented, and both the opportunities and challenges will be discussed. |
Wednesday, March 16, 2022 3:24PM - 3:36PM |
Q57.00003: Enhanced absorption of hydrogen in ball milled lanthanum for hydride formation Peter A Sharma, Sakun Duwal, Vitalie Stavila, Jason R Jeffries, Jesse S Smith, Yue Meng, Dean Smith
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Wednesday, March 16, 2022 3:36PM - 3:48PM |
Q57.00004: Effect of metamaterial engineering on the superconductive properties of ultrathin layers of NbTiN Vera N Smolyaninova, William Korzi, Grace Yong, Anne-Marie Valente-Feliciano, Joseph C Prestigiacomo, David R Beverstock, Michael S Osofsky, Igor I Smolyaninov
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Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q57.00005: Massive electrons resolve the puzzles of room-temperature superconductivity in Superhydrides Theja De Silva The recent discovery of room-temperature superconductivity, under extreme pressure in hydrogen-rich materials, has attracted tremendous attention. The superconductivity of these materials was confirmed by the observation of zero-resistance, isotope effects, effect of magnetic field, and other standard properties. However, some of the experimental features were puzzling as they were not consistent with the known superconductivity theories. In this talk, we present a concept of massive electrons due to the extreme pressure and successfully explain all nonstandard experimental observations. We show that our massive electron concept explains the large effective mass of the quasiparticles, the reason for the high critical temperatures for moderate electron-phonon couplings, and a 3–5 orders of magnitude larger conductivity causing a narrow resistivity broadening at the transition. |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q57.00006: Physical Properties, Charge Density Waves, and Superconductivity in Ca3(RhxIr1-x)4Sn13 Elizabeth H Krenkel, Makariy A Tanatar, Sunil Ghimire, Kamal R Joshi, Erik I Timmons, Ruslan Prozorov, Marcin Konczykowski, Romain Grasset, Shuzhang Chen, Cedomir Petrovic The coexistence of charge-density wave ordering (CDW) and superconductivity (SC) was studied in the "3-4-13" stannides, Ca3(RhxIr1-x)4Sn13, using transport and magnetic measurements. Long-range CDW order coexists with superconductivity up to some concentration between x=0.6 and x=0.7 where the CDW transition terminates at the quantum critical point (QCP). Typically for CDW/SC systems, a short-range CDW still persists beyond critical concentration, maybe even up to x=1. Our earlier report of the effects of electron irradiation in the stoichiometric compounds was extended to alloys in this study, including the QCP composition. A large rate of Tc suppression combined with fully-gapped superconductivity point to unconventional pairing in this system. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q57.00007: The Role of Impurities on the Electronic and Superconducting Properties of NiBi3 Jarryd Horn, Johnpierre Paglione, Jihun Park, Ichiro Takeuchi, John C Collini Superconductivity in the bismuth-nickel system has been of interest due to both the discovery of triplet p-wave superconductivity in bilayer films and the possible competition between superconductivity and magnetic order that has been measured in single-crystal NiBi3. While previous literature suggests that the presence of amorphous nickel may be the source of the previously reported ferromagnetic order in NiBi3, the effect of bismuth impurities on the electronic properties are rarely addressed. Understanding the role of these extrinsic effects calls for a more careful investigation of the electronic properties of NiBi3. In order to address this, we have grown NiBi3 samples by bismuth flux (as have all previously reported NiBi3 single crystal samples) as well as by chemical vapor transport (CVT). In this talk, we present magnetotransport studies of flux- and CVT-grown NiBi3 samples which reveal large discrepancies in the electronic properties both between samples and between different sections of the same sample that suggest that bismuth impurities play a significant role in the normal state and superconducting properties of NiBi3. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q57.00008: Low Temperature Annealing and the Origins of Superconductivity at Nickel Bismuth Interfaces Matthew Vaughan, Nathan Satchell, Christy J Kinane, Gavin Stenning, Sean Langridge, Gavin Burnell It has been suggest that Nui/Bi interfaces may host unconventional superconductivity in thin-film bilayers. We have studied the structural, magnetic, and superconducting properties of sputter deposited Bi/Ni bilayers. In the as-grown state, our films do not display a superconducting transition; however, when stored at room temperature, after about 14 days they develop a superconducting transition up to 3.8 K. To systematically study the effect of low temperature annealing on our bilayers, we performed structural characterization with x-ray diffraction and polarized neutron reflectometry, along with magnetometry and low-temperature electrical transport measurements on samples annealed at 70°C . We find that the onset of superconductivity in our samples is coincident with the formation of ordered NiBi3 intermetallic alloy, a known s-wave superconductor. We calculate that the annealing process has an remarkably low activation energy of ( 0.86 ± 0.06 ) eV . As a consequence, gentle heating of the bilayers will cause formation of the superconducting NiBi 3 at the Ni/Bi interface, which poses a challenge to studying any distinct properties of Bi/Ni bilayers without degrading that interface. |
Wednesday, March 16, 2022 4:36PM - 4:48PM |
Q57.00009: Prediction of High Temperature Superconductivity in Solid Hydrogen Mehmet Dogan, Marvin L Cohen, Sehoon Oh Recent experiments on solid hydrogen at high pressures provide critical information about its crystal phase. In particular, Loubeyre et al. tracked the direct band gap and vibron frequency of hydrogen via infrared measurements up to ~425 GPa [1]. We have shown that the data are consistent with the molecular C2/c-24 phase, which can explain the observed behavior up to ~425 GPa and above [2]. However, there is still the possibility of a structural phase transition or a series of transitions above this pressure. If such transitions occur, the most likely candidate phases are the (molecular) Cmca-12 and Cmca-4 and the (atomic) I41/amd-2 phases. In this work, we employ a Wannier function-based dense k-point and q-point sampling to compute the electron-phonon coupling and superconducting properties of solid hydrogen in these four phases. We find that the C2/c-24 phase has a high superconducting transition temperature of 242 K at 500 GPa, and the transition temperature rapidly increases with pressure in the 400 – 500 GPa range [3]. We also find that the Cmca-12 phase follows the same trend with a superconducting transition temperature of 212 K at 500 GPa, whereas the Cmca-4 and I41/amd-2 phases show less pressure-dependent behavior [4]. These properties can be used to distinguish between crystal phases in future experiments. |
Wednesday, March 16, 2022 4:48PM - 5:00PM |
Q57.00010: Superconductivity in hydrogen sulfide in the presence of carbon Yuki Sakai, James R Chelikowsky, Marvin L Cohen |
Wednesday, March 16, 2022 5:00PM - 5:12PM |
Q57.00011: Inducing chiral superconductivity on honeycomb lattice systems Abdulrhman Alsharari Superconducting pairing correlations have a great impact on the topological properties of the quasiparticles in honeycomb lattice systems. We utilize a Bogolyubov-de Gennes (BdG) Hamiltonian with a relative chemical potential shift between the particle and hole terms, and consider nearest-neighbor and next nearest-neighbor chiral spin-singlet (chiral d-wave superconductivity that is the preferred channel in some graphene models). With the application of a uniform magnetic field, the system exhibts non-trivial topological behavior. |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q57.00012: Absence of conventional room-temperature superconductivity at high pressure in carbon-doped H3S Tianchun Wang Recently, it has been reported that room-temperature superconductivity with Tc ~ 280 K emerges in carbonaceous sulfur hydride (C-S-H) system under high pressure up to 270 GPa1. Since their atomic configuration is still not determined, we explore a variety of crystal srutcutre in a C-S-H convex hull and discuss the stability of candidate structures of C-S-H ternary compounds2. |
Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q57.00013: Multifractally-enhanced superconductivity in thin films Igor Burmistrov The multifractal superconducting state originates from the interplay of Anderson localization and interaction effects. In this article we overview the recent theory of the superconductivity enhancement by multifractality and extend it to describe the spectral properties of superconductors on the scales of the order of the superconducting gap. Specifically, using the approach based on renormalization group within the nonlinear sigma model, we develop the theory of a multifractal superconducting state in thin films. We derive a modified Usadel equation that incorporates the interplay of disorder and interactions at energy scales larger than the spectral gap and study the effect of such an interplay on the low-energy physics. We determine the spectral gap at zero temperature which occurs to be proportional to the multifracally enhanced superconducting transition temperature. The modified Usadel equation results in the disorder-averaged density of states that, near the spectral gap, resembles the one obtained in the model of a spatially random superconducting order parameter. We reveal strong mesoscopic fluctuations of the local density of states in the superconducting state. Such strong mesoscopic fluctuations imply that the interval of energies in which the superconducting gap establishes is parametrically large in systems with multifractally-enhanced superconductivity. |
Wednesday, March 16, 2022 5:36PM - 5:48PM |
Q57.00014: Band Interplay and Finite-Bandwidth Effects on the Superconducting Critical Temperature of Heavily Disordered Interfaces Hosting Multi-band Superconductivity Giulia Venditti, Sergio Caprara, Marco Grilli LaAlO3/SrTiO3 interfaces are a nice example of a two-dimensional electron gas, whose carrier density can be varied by top- and back-gating techniques. The interplay of two-dimensionality, multi-band character and disorder affects the superconducting critical temperature Tc of these heavily disordered multi-band superconductors. In this framework, finite-bandwidth effects are called for a better understanding, as well as the attractive or repulsive nature of the bands involved. |
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