Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D43: Topological Superconductivity in Engineered HeterostructuresFocus
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Sponsoring Units: DMP Chair: Cui-Zu Chang, The Pennsylvania State University; Igor Zutic, State Univ of NY - Buffalo Room: Room 317 |
Monday, March 6, 2023 3:00PM - 3:36PM |
D43.00001: Towards Topological Superconductivity in Epitaxial Superconductor-Semiconductor Systems Invited Speaker: Javad Shabani
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Monday, March 6, 2023 3:36PM - 3:48PM |
D43.00002: Interface-Induced Superconductivity in MnBi2Te4/FeTe Heterostructures Zijie Yan, Wei Yuan, Hemian Yi, Zihao Wang, Yi-Fan Zhao, Ruoxi Zhang, Lingjie Zhou, Deyi Zhuo, Cui-Zu Chang The interface of two materials can and has been shown to give rise to completely unexpected emergent phenomena, such as interface-induced superconductivity. Moreover, when one of the two materials has a strong spin-orbit coupling, this interface-induced superconductivity may host the topological superconducting phase. In this work, we use molecular beam epitaxy (MBE) to synthesize the MnBi2Te4/FeTe heterostructures. MnBi2Te4, a tetradymite-type compound, was recently predicted and experimentally demonstrated to be a topological insulator with intrinsic antiferromagnetism and extremely strong spin-orbit coupling. FeTe is also an antiferromagnetic material and non-superconducting. By performing high-resolution scanning transmission electron microscopy measurements, we observe an atomically sharp interface across the septuple-layer structure of MnBi2Te4 and the trilayer structure of FeTe. Moreover, our transport measurements uncover a sharp superconducting transition with a zero resistance Tc ~9.3 K. The nonzero anomalous Hall traces appear at temperatures greater than Tc and persist up to ~24 K. The latter value is consistent with the Néel temperature of our MBE-grown MnBi2Te4 films. Our successful synthesis of MnBi2Te4/FeTe heterostructures with atomically sharp interfaces will advance the fundamental inquiries into the topological superconducting phase in hybrid devices and may provide an alternative approach for the exploration of the topological superconducting phase. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D43.00003: Tunable Planar Josephson Junctions Driven by Time-Dependent Spin-Orbit Coupling David Monroe, Mohammad Alidoust, Igor Zutic Integrating conventional superconductors with common III-V semiconductors provides a versatile platform to implement tunable Josephson junctions (JJs) and their applications. We propose that with gate-controlled time-dependent spin-orbit coupling, it is possible to strongly modify the current-phase relations and Josephson energy and provide a mechanism to drive the JJ dynamics, even in the absence of any bias current[1]. We show that the transition between stable phases is realized with a simple linear change in the strength of the Rashba spin-orbit coupling, while the transition rate can exceed the gate-induced electric field GHz changes by an order of magnitude. The resulting interplay between the constant effective magnetic field and changing Rashba spin-orbit coupling has direct implications for superconducting spintronics, controlling Majorana bound states, and emerging qubits. We argue that topological superconductivity, sought for fault-tolerant quantum computing, offers simpler applications in superconducting electronics and spintronics. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D43.00004: Josephson Junction Dynamics with Rashba and Dresselhaus Spin-Orbit Coupling David Monroe, Dario Tringali, Alexander Quinn, Mohammad Alidoust, Igor Zutic Planar Josephson junctions (JJs) provide a suitable platform to realize topological superconductivity. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D43.00005: Influence of disorder on vortex Majorana states in 3D topological insulators Jukka Vayrynen, Rafal Rechcinski, Dmitry I Pikulin, Roman M Lutchyn Majorana states hosted in vortex cores of topological insulator/superconductor |
Monday, March 6, 2023 4:24PM - 4:36PM |
D43.00006: Supercurrent in superconductor-topological insulator-superconductor junctions with vortices Aleksei Khindanov, Jukka Vayrynen, Rafal Rechcinski, Dmitry I Pikulin, Roman M Lutchyn Topological insulator-superconuctor (TI-SC) heterostructures are a promising platform for creation and manipulation of Majorana Zero Modes (MZMs). Vortices in such heterostructures are theorized to bind MZMs, while SC-TI-SC junctions can potentially be used to fuse MZMs. In this work, we numerically investigate the relative strength of the trivial 2π and topological 4π contributions to the supercurrent in SC-TI-SC junctions with vortices, and using these results develop a MZM fusion protocol in such systems. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D43.00007: Edge Transport in Quantum Spin Hall Insulator-Superconductor Heterostructures Joseph J Cuozzo, Enrico Rossi, Wei Pan For heterostructures formed by a quantum spin Hall insulator (QSHI) placed in proximity of a superconductor (SC), no external magnetic field is necessary to drive the system into a phase supporting Majorana bound states. This fact makes QSHI-SC very attractive for the realiation of non-Abelian electronic states and fault-tolerant qubits. A QSHI state can be realized in double quantum wells formed by InAs and GaSb by properly choosing the relative thickness of InAs and GaSb. In this talk, I will present theoretical and experimental results for the transport properties of QSHI-SC heterostructures formed by a InAs/GaSb double quantum well, designed to be in the QSHI phase, and superconducting Ta. In particular we studied the dependence of the differential conductance on the magnitude of an external magnetic field, B. Our detailed theoretical results show that the dependence of the differential conductance on B is affected by the position, in energy, of the Dirac point for the helical modes. In particular, I will show the difference between the transport properties of QSHI-SC systems in which the Dirac point is within the bulk gap, and those in which the Dirac point is "buried", i.e., below the top of the bulk valence band. By comparing the theoretical results to the experimental measurements we conclude that in our current devices the Dirac point is buried. I will then discuss the implications of having a buried Dirac point for the realization of Majorana bound states in QSHI-SC devices. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D43.00008: Nanofabrication of Sn-based superconductor / topological Dirac semimetal heterostructures Keita Ishihara, Le Duc Anh, Tomoki Hotta, Masaaki Tanaka The superconductor/topological-material heterostructures attract attention as a platform of unconventional superconductivity. Among various topological material candidates, α-Sn is attractive because it can exhibit a wide range of topological phases from topological Dirac semimetal to topological insulator. Moreover, upon heating α-Sn undergoes a phase transition to β-Sn, which becomes superconducting at low temperature (< 4 K). In this study, we utilize this rich phase diagram of Sn to fabricate superconducting β-Sn/topological Dirac semimetal α-Sn planar junctions. Epitaxial α-Sn thin films are partially transformed to β-Sn under Ga ion-beam irradiation, which exhibits superconductivity at 3.8 K. By focusing the ion beam, we successfully fabricate β-Sn nanowire structures with less than 200 nm in width. In the presentation, we will discuss the structure and superconducting properties of the nanostructure in detail. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D43.00009: Topological nodal-point superconductivity in a 2D-antiferromagnet/superconductor hybrid system Roberto Lo Conte, Maciej Bazarnik, Eric Mascot, Dirk K Morr, Kirsten von Bergmann, Roland M Wiesendanger In the recent years, pioneering studies have been carried out on magnet/superconductor hybrid systems [1-4], motivated by their potential to host emergent quantum phases such as topological superconductivity [5]. So far, the attention has been mainly focused on hybrid systems with a ferromagnetic order [1,3,4,6], which are understood as gapped topological superconductors with a finite Chern number [7,8] defining the amount of end states and propagating edge modes. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D43.00010: Superconducting diode effect in InAs/Al Josephson junctions at high in-plane magnetic fields Neda Lotfizadeh, PENG YU, William M Strickland, Mohammad Farzaneh, Baris Pekerten, Alex Matos-Abiague, Javad Shabani Nonreciprocal critical current in superconducting Josephson junctions occurs when the critical current Ic depends on the direction the current was swept and can be observed by breaking the time reversal and inversion symmetries in the system. Recently, there has been a surge of interest in studying the superconducting diode effect due to its possible application in electronic circuits, sensors, and detectors. In this work, we study epitaxial InAs/Al Josephson junctions with various superconductor width in the presence of in-plane magnetic fields. By applying a magnetic field parallel to the junction, we observe nonreciprocal critical current which is due to the strong Rashba spin-orbit interaction in the system. However, by reducing the width of the superconducting lead, we observe a change in sign of ΔI=I(+)-I(-) as we increase the in-plane magnetic field. We discuss the possible mechanisms and possibility of finite momentum pairing. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D43.00011: Tunneling spectroscopy of DC voltage biased planar Josephson junctions in a hybrid Al/InAs two-dimensional electron gas heterostructure Teng Zhang, Tyler Lindemann, Michael J Manfra Planar Josephson junctions (JJs) fabricated on a hybrid epitaxial Al-InAs two-dimensional electron gas (2DEG) heterostructure are a rich playground for exploration of topological superconductivity. The combination of a gate-tunable semiconductor possessing low disorder, strong spin-orbit coupling, and large g-factor with a s-wave superconductivity allows for examination many possible state configurations. DC voltage-biased planar JJs are predicted to host Majorana zero and Floquet Majorana modes simultaneously at their two ends. Here, we fabricate and measure gate-tunable planar JJs on epitaxial Al-InAs 2DEGs with two tunneling probes for measuring the density of states at two ends of the junction. We report on the density of states at two ends of the junction as a function of the DC bias voltage across the junction, the in-plane magnetic field, and the electron density in the junction. Comparisons to theoretical expectations are made. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D43.00012: Hybridization and Fusion of Majorana Bound States in Topological Planar Josephson Junctions Tong Zhou, Jong E Han, Alex Matos-Abiague, Javad Shabani, Igor Zutic Majorana bound states (MBS) with their nonlocal degrees of freedom and non-Abelian statistics have been viewed as a promising candidate for achieving fault-tolerant topological quantum computing. However, despite intensive efforts, experimental support for MBS remains indirect and does not probe their crucial non-Abelian statistics. The recent discovery of topological planar Josephson Junctions (JJs) provides a new promising platform with a large parameter space and multiple effective control for MBS [1-4]. A significant advantage of JJs is the tunable superconducting phase difference, which acts as an additional knob to control the topological phase [3]. Taking this advantage, we propose a novel platform of non-collinear JJs to manipulate MBS with phase control based on the fabrication of InAs/Al JJs. This adaptable implementation reveals how tuning the superconducting phase difference can generate, hybridize, and fuse multiple MBS pairs. By analyzing the influence of the geometry, gate voltage, and magnetic field, we demonstrate the optimal parameter space for the experimental realization of MBS and their fusion, as an important step toward non-Abelian statistics. |
Monday, March 6, 2023 5:48PM - 6:00PM |
D43.00013: Interface-Induced Superconductivity in Quantum Anomalous Hall-Iron Chalcogenide Heterostructures Hemian Yi, Ying-Ting Chan, Jiaqi Cai, Xianxin Wu, Zijie Yan, Yi-Fan Zhao, Lingjie Zhou, Ruoxi Zhang, Ruobing Mei, Run Xiao, Ke Wang, Anthony R Richardella, John Singleton, Laurel E Winter, Moses H Chan, Nitin Samarth, Xiaodong Xu, Weida Wu, Chaoxing Liu, Cui-Zu Chang When two different electronic materials are brought together, the resultant interface often shows unexpected quantum phenomena, including interfacial superconductivity and Fu-Kane topological superconductivity. In this work, we use molecular beam epitaxy (MBE) to synthesize heterostructures formed by interfacing two magnetic materials, a ferromagnetic topological insulator with the quantum anomalous Hall (QAH) state and an antiferromagnetic iron chalcogenide (FeTe). We demonstrate the coexistence of superconductivity, ferromagnetism, and topological band structure in these QAH/FeTe heterostructures, the three essential ingredients of chiral topological superconductivity. Moreover, we find that the upper critical magnetic field is anisotropic near the superconducting temperature Tc but becomes isotropic and exceeds the Pauli paramagnetic limit for conventional superconductors at low temperatures, implying an unusual superconducting pairing mechanism. The QAH/FeTe heterostructures with robust superconductivity and atomically sharp interfaces provide an ideal platform for the exploration of chiral topological superconductivity and Majorana physics, constituting an important step toward scalable topological quantum computation. |
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