Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session W42: Superconductivity in Topological SystemsFocus

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Sponsoring Units: DMP Chair: Javad Shabani, New York University Room: Room 318 
Thursday, March 9, 2023 3:00PM  3:36PM 
W42.00001: Superconducting proximity effect in topological Dirac materials Invited Speaker: Chuan Li Inducing superconductivity in topological materials stimulates the formation of novel quantum states of matter, including the Majorana zero mode. Besides the original prediction in 3D topological insulators, the notion of topological phases has been generalized to different dimensions and extended to the higherorder states. 
Thursday, March 9, 2023 3:36PM  4:12PM 
W42.00002: Quasi2D Fermi surface of superconducting linenodal metal CaSb_{2} Invited Speaker: Atsutoshi Ikeda

Thursday, March 9, 2023 4:12PM  4:24PM 
W42.00003: Measuring Induced gap of InAs/NbTiN using quantum point contacts in Integer Quantum Hall regime Mehdi Hatefipour, Ashley Argueta, William M Strickland, Ido Levy, Enrico Rossi, Javad Shabani

Thursday, March 9, 2023 4:24PM  4:36PM 
W42.00004: Datadriven identification of connate topological superconductor candidates Aurland Hay, Ram Seshadri One way to achieve topological superconductivity is through identifying a bulk swave superconductor that also exhibits topological surface states. The resulting “connate” topological superconductor functions through the selfproximity effect similar to the interfacial proximity effect within topological superconductor heterostructures. While nontrivial electronic structure topology can be predicted through firstprinciples calculations, superconductivity is difficult to predict a priori, limiting broad screening for materials that combine both phenomena. Here, we present a datadriven approach to compile a catalog of potential connate topological superconductor materials, starting with experimentallyconfirmed superconductors and crossreferencing their topological nature via highthroughput computational data. Additionally, subtle pitfalls in the calculation of Z_{2} topological invariants for materials without welldefined band gaps (such as superconductors) will be discussed. 
Thursday, March 9, 2023 4:36PM  4:48PM 
W42.00005: Monolayer WTe_{2} superconductivity from repulsive interactions Ammar Jahin Superconductivity has been observed in WTe_{2}. However the exact nature of the order parameter is yet unclear. Furthermore, it has been proposed that with a pwave pairing, the material is a secondorder topological superconductor with a pair of Majorana zero modes at the corners of a finite sample. We show that the desired pwave state arises naturally as a consequence of the KohnLuttinger mechanism. We further study the behaviour of the system in response to external inplane magnetic fields. We find an enhancement to the critical temperature that depends on the direction of the magnetic field. 
Thursday, March 9, 2023 4:48PM  5:00PM 
W42.00006: Understanding disorder in InAs quantum wells on metamorphic IIIV buffer layers for topological Josephson junction Ido Levy, William M Strickland, Mehdi Hatefipour, Ashley Argueta, Lukas J Baker, Melissa E Mikalsen, Dylan Langone, Mohammad Farzaneh, Javad Shabani

Thursday, March 9, 2023 5:00PM  5:12PM 
W42.00007: α and βphases of Sn thin films grown on GaSb(001) surface by molecular beam epitaxy Anjali Rathore, Pradip Adhikari, Chandima Edirishinghe, Gyehyeon Kim, Hyoungtaek Lee, Rachel Woodrum, Sinchul Yeom, HyeongRyeol Park, Changhee Sohn, Benjamin J Lawrie, Mina Yoon, Matthew Brahlek, Joon Sue Lee Tin (Sn) is known to show distinct phases depending on temperature and pressure. The cubic αSn is stable below 13.7 C for bulk (higher for thin films), while tetragonal βSn is well known metallic phase present at room temperature and shows superconductivity at 3.7 K. Recently, Sn is gaining interest as a unique and promising candidate because of various topological phases of αSn by tuning strain, orientation, and thickness configurations as well as excellent superconducting features of βSn for quantum devices. We investigate Sn thin films with different α and βphases on GaSb(001) surface using molecular beam epitaxy with active liquid Nitrogen cooling as well as by firstprinciples calculations. We observed βSn(110), βSn(001), and αSn(110) phases with varying growth temperatures for the same film thickness (40 nm). Transport measurement revealed superconductivity for βSn(001) phase whereas no superconductivity and large weak localizationlike features were seen down to 0.04 K for βSn(110) phase. We also study the crystal structure with temperaturedependent Raman spectroscopy. This work highlights a strong connection among novel electronic phases and structure metastability that is critical for controlling the topological and superconducting nature of Sn. 
Thursday, March 9, 2023 5:12PM  5:24PM 
W42.00008: Superconducting properties of Ta_{3}Sb and Ti_{3}Sb, A15 compounds which are candidate topological superconductors Matthew P Smylie, Ramakanta Chapai, Andreas Rydh, Jared Z Dans, Hendrik Hebbeker, Duck Young Chung, Hong Zheng, Alexei E Koshelev, John Pearson, WaiKwong Kwok, John F Mitchell, Ulrich Welp We present a study of the superconducting properties of polycrystalline Ti_{3}Sb (T_{c} ~ 5.9 K) and Ta_{3}Sb (T_{c} ~ 0.67 K), candidate topological superconductors of the A15 family. Via magnetotransport, magnetization and calorimetry measurements, we determine the superconducting phase diagram for both compounds and find large GinsburgLandau parameters for both Ti_{3}Sb (κ = 55) and Ta_{3}Sb (κ = 90) , identifying them as extremely typeII superconductors. Calorimetry and London penetration depth measurements at ^{3}He temperatures are consistent with a full BCSlike superconducting gap in both compounds. 
Thursday, March 9, 2023 5:24PM  5:36PM 
W42.00009: Probing for topological signatures in phasecontrolled multiterminal Josephson junctions Maxwell Wisne, Venkat Chandrasekhar, Pertti J Hakonen, Ilari Lilja Andreev bound states in SNS junctions depend periodically on the Josephson phase φ between two superconductors, resembling the periodic dispersion of electron energy levels in a crystal lattice. A normal metal connected to n superconductors corresponds to a n1 dimensional crystal. It has been predicted that the resulting “band structure” of such multiterminal Josephson junction devices may be topological [1]. In the case where the normal metal is diffusive, the quasiparticle density of states at the Fermi energy varies periodically with the phases, with gapped regions separated by regions where the gap completely closes. The dependence of the density of states can be probed by measuring the resistance of suitably designed diffusive devices [2]. We report on the fabrication and measurement of 3 terminal diffusive and ballistic devices, using a sample design that permits us to vary the two distinct phases independently. 
Thursday, March 9, 2023 5:36PM  5:48PM 
W42.00010: Topological Aspects of ElectronPhonon Coupling Jiabin Yu, Chris Ciccarino, Raffaello Bianco, Yuanfeng Xu, ChaoXing Liu, Ion Errea, Prineha Narang, B. Andrei Bernevig Electronphonon coupling is crucial for various quantum phases, including superconductivity and chargedensity wave. We revealed the topological aspects of the electronphonon coupling strength. In particular, we derived topological lower bounds for the total electronphonon coupling strength in certain systems with Fermi surfaces. Implications on other systems will also be discussed. 
Thursday, March 9, 2023 5:48PM  6:00PM 
W42.00011: Pair Density Waves and Superconductivity in the πflux Hofstadter Model using MeanField and Renormalization Group Analyses Daniel Shaffer, Luiz H Santos The πflux lattice, or equivalently the Hofstadter model with magnetic flux of half of the flux quantum per unit cell, has historically attracted attention in the context of the pseudogap phase of cuprate superconductors and the study of systems with Dirac fermions, located at half filling in the πflux lattice. Recently it has become possible to realize the πflux lattice in cold atomic systems and moiré materials. In our work we consider the model away from halffilling and study the possibility of weak coupling instabilities in the presence of extended Hubbard interactions occuring around the lessstudied fillings corresponding to Van Hove singularities. Using both meanfield and renormalization group calculations, we find that paring instabilities, including swave and dwave uniform superconductors (SC) and a triplet pair density wave (PDW), in general win over competing spin density wave instabilities. Of particular interest is the PDW phase, for which some evidence has been seen in cuprates. This phase is characterized by spontaneous formation of Cooper pairs with total nonzero momentum without an explicit breaking of time reversal symmetry, as opposed to the FFLO state. We find that the triplet PDW phase is realized in the πflux lattice with repulsive onsite interactions together with a moderately small nearestneighbor attractive interactions, making it the first model in which a PDW phase is realized at weak coupling as a symmetryenforced logarithmic instability. 
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