Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session B48: Superconductivity in Low Dimensional Systems |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Hongchao Xie, Univ of Michigan - Ann Arbor Room: Mile High Ballroom 1A |
Monday, March 2, 2020 11:15AM - 11:27AM |
B48.00001: Quantum spin-liquid and chiral superconductivity in TaS2 Amit Kanigel, Amit Ribak, Roni Majlin skiff, Mark H Fischer, Jonathan Ruhman, Yoram Dagan Van der Waals (vdW) materials offer unprecedented control of electronic properties via stacking of different types of two-dimensional materials. A fascinating frontier, largely unexplored, is the stacking of strongly correlated phases of matter. We study 4Hb-TaS2, which naturally realizes an alternating stacking of 1T-TaS2 and 1H-TaS2 structures. The former is a well-known Mott insulator, which has recently been proposed to host a gapless spin-liquid ground state . The latter is a superconductor known to also host a competing charge density wave state. This raises the question of how these two components affect each other when stacked together. We find a superconductor with a Tc of 2.7 K and anomalous properties, of which the most striking one is a signature of time-reversal-symmetry breaking, abruptly appearing at the superconducting transition. This observation is consistent with a chiral superconducting state. |
Monday, March 2, 2020 11:27AM - 11:39AM |
B48.00002: Blockade of vortex flow by thermal fluctuations in atomically thin clean-limit superconductors Avishai Benyamini, Dante Kennes, Evan Telford, Kenji Watanabe, Takashi Taniguchi, Andrew Millis, James C Hone, Cory Dean, Abhay Narayan Resistance in superconductors arises from the motion of vortices driven by flowing supercurrents or external electromagnetic fields and may be strongly affected by thermal or quantum fluctuations. The common expectation borne out in previous experiments is that as the temperature is lowered, vortex motion is suppressed, leading to a decreased resistance. A new generation of materials provides access to the previously inaccessible regime of clean-limit superconductivity in atomically thin superconducting layers. We show experimentally that for few-layer 2H-NbSe2 the resistance below the superconducting transition temperature may be non-monotonic, passing through a minimum and then increasing again as temperature is decreased further. The effect exists over a wide range of current and magnetic fields but is most pronounced in monolayer devices at intermediate currents. Analytical and numerical calculations confirm that the findings can be understood in a two-fluid vortex model, in which a fraction of vortices flow in channels while the rest are pinned but thermally fluctuating in position, effectively controlling the mobility of the free vortices. The findings provide a new perspective on fundamental questions of vortex mobility and dissipation in superconductors. |
Monday, March 2, 2020 11:39AM - 11:51AM |
B48.00003: Supercurrent detection of topologically trivial zero-energy states in nanowire junctions Oladunjoye Awoga, Jorge Cayao, Annica M Black-Schaffer In this work we investigate phase-biased transport in SNS junctions based on nanowires, with strong Rashba spin-orbit coupling and magnetic field, strongly coupled to 2D conventional $s$-wave superconductors. We find that all the nanowire parameters are renormalized, in a manner dependent on the width of the superconductor. In particular, we show that the finite width of the superconductor induces a finite energy shift, or effective chemical potential, in the nanowire sectors coupled to the two superconductors, thus leading to a natural formation of a quantum dot at the junction. Remarkably, under these conditions, the junction supports the emergence of a pair of zero-energy states in the trivial phase, i.e. false Majorana fermion states. We demonstrate that this effect is highly tunable by the superconductor width, and suggest this as an explanation for the formation of trivial zero-energy states reported in recent experiments. Most importantly, we show that these zero-energy states produce a $\pi$-shift in the phase-biased supercurrent. This gives access to a simple tool for their unambiguous detection, thus ruling out any Majorana-like interpretation. See Phys. Rev. Lett. 123, 117001 (2019) for further details. |
Monday, March 2, 2020 11:51AM - 12:03PM |
B48.00004: Quantum disoliton as a one-dimensional linear potential system Geunyong Kim, Jinho Yang, Ilkyu Yang, Dirk Wulferding, Jinyoung Yun, Roman Movshovich, GilYoung Cho, Ki-Seok Kim, Jeehoon Kim Disoliton as a bounded soliton system appeared initially in a swimming pool in the form of half vortex ring. Subsequently, it turns out to be a universal phenomenon at all length scales. Despite the discovery of several disoliton systems, their underlying physics such as nature of an interaction potential remains elusive due to the lack of a model system allowing controllability and repeatability. Here we report on a quantum disoliton (QDS) created as a U-shape quantum flux tube in a superconducting Nb film. A systematic control on a single QDS reveals the purported 1D linear potential, i.e. distance-independent force. The QDS will provide a novel platform for exploring 1D phase transition, quantum transport, and non-Abelian statistics. |
Monday, March 2, 2020 12:03PM - 12:15PM |
B48.00005: Andreev bound states in hybrid full-shell Al/InAs nanowire devices Marco Valentini, Matthias Brauns, Andrea Hofmann, Peter Krogstrup, Georgios Katsaros Hybrid superconductor-semiconductor nanowire (NW) devices have attracted widespread interest as they can host Majorana zero modes (MZMs). While most of the previous experiments dealt with semiconductor NWs partially covered by a superconductor, a recent theory proposal [1] suggests to fully cover the semiconductor NWs with a superconductor. One of the main advantages of having a superconducting full-shell is that MZMs should arise at a very precise magnetic field, namely in the odd lobes of the Little-Parks effect. A first result [2] showed the presence of a zero bias peak (ZBP) in the first lobe, suggesting the presence of MZMs in such NWs. However, also Andreev bound states (ABS) could arise in such experiments. Hence, it is important to study them and especially their evolution in a magnetic field. Here, we present low temperature magnetotransport data using InAs NWs fully covered by Al [3]. We investigate ABS in the Little-Parks regime; we show that ABS can merge at zero bias in the first lobe, mimicking MZMs behaviour. Furthermore, we suggest how to discriminate ZBPs arising from MZMs and from ABS. |
Monday, March 2, 2020 12:15PM - 12:27PM |
B48.00006: Gate-tunable superconductivity in layered β-MoTe2 Apoorv Jindal, Daniel A Rhodes, Kenji Watanabe, Takashi Taniguchi, Cory Dean, James C Hone, Abhay Pasupathy van der Waals heterostructures of mechanically-exfoliated crystalline materials are a platform to observe quantum phenomena in the low-disorder limit. Of special interest are materials with low carrier density, where the use of electrostatic doping and electric field tuning of bandstructure gives us easily accessible experimental tuning knobs. Twisted graphene and TMD superlattices, and monolayer WTe2 are a couple of striking recent examples. In monolayer WTe2, the use of gate potentials has been shown to tune between a topological insulator and a superconducting phase. In this talk, we describe transport measurements on a closely related material, β-MoTe2. We show that β-MoTe2 exhibits robust gate-tunable superconductivity in the few-layer limit. hBN encapsulated devices in the monolayer exhibit a superconducting critical temperature of ~ 6 K, a nearly hundred-fold enhancement over the bulk value. Using a dual-gated device structure, we also observe a strong dependence of superconducting properties on carrier density and displacement field. In this talk, we will fully characterize the layer, carrier density, displacement field, and magnetic field phase diagrams of this material. |
Monday, March 2, 2020 12:27PM - 12:39PM |
B48.00007: Non-linear IV characteristics in two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics vs inhomogeneity Lara Benfatto, Giulia Venditti, Johan Biscaras, Simon Hurand, Nicolas Bergeal, Jerome Lesueur, Anjana Dogra, Ramesh Budhani, Mintu Mondal, John Jesudasan, Pratap Raychaudhuri, Sergio Caprara One of the hallmarks of the Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconductors is the universal jump of the superfluid density, that can be indirectly probed via the non-linear exponent of the current-voltage IV characteristics. Here, we compare the experimental measurements of IV characteristics in two cases, namely NbN thin films and SrTiO3-based interfaces. While the former display a paradigmatic example of BKT-like non-linear effects, the latter do not seem to justify a BKT analysis. Rather, the observed IV characteristics can be well reproduced theoretically by modelling the effect of mesoscopic inhomogeneity of the superconducting state. Our results offer an alternative perspective on the spontaneous fragmentation of the superconducting background in confined two-dimensional systems. |
Monday, March 2, 2020 12:39PM - 12:51PM |
B48.00008: Two-dimensional superconductivity and violation of Pauli paramagnetic limit in MBE-grown Al nanofilms Chi-Te Liang, Ching-Chen Yeh, Guan-Ming Su, Ankit Kumar, Biyi Wu, Yen-Ting Fan, Sheng-Di Lin, Lee Chow We have performed low-temperature transport measurements on Al nanofilms on GaAs substrates prepared by molecular beam epitaxy (MBE) with as-grown thicknesses of 3 nm, 3.5 nm, and 4 nm. Such MBE-grown nanofilms all show the Berezinskii-Kosterlitz-Thouless transition, which is compelling evidence for two-dimensional superconductivity, with enhanced transition temperatures (≈2.3 K) compared to that of bulk Al (1.2 K). When the magnetic field is applied parallel to the plane of the Al nanofilms, we measure the upper critical magnetic field Hc∥ by the mid-points of resistive transitions at different temperatures T . In this way, we can estimate Hc∥(T=0). It is found that Hc∥(T=0) increases with decreasing film thickness. Interestingly, for the thinnest device, Hc∥(T=0) exceeds the Pauli paramagnetic limit. Such experimental results can be ascribed to spin-orbit coupling effects on superconductivity, even though Al has a low atomic mass. |
Monday, March 2, 2020 12:51PM - 1:03PM |
B48.00009: Superconducting Nanostructures Grown by He+- Focused Ion Beam Induced Deposition (FIBID) Rosa Córdoba, Pablo Orús, Dominique Mailly, Gregor Hlawacek, JOSE MARIA DE TERESA NOGUERAS W-C superconducting nanostructures have been grown by He+ - Focused Ion Beam Induced Deposition (He+-FIBID), which allows superb lateral resolution as well as the capability for creating three-dimensional nanostructures. First, results on in-plane W-C superconducting nanowires grown by He+-FIBID will be presented, where the long-range vortex transport has been investigated by means of non-local measurements; and we will compare them with previous research on in-plane nanostructures grown by Ga+-FIBID [1]. Secondly, results on the growth and superconducting properties of out-of-plane nanotubes with well-controlled inner and outer diameter grown by He+-FIBID will be shown [2]. Lastly, results on the growth and superconducting properties of nanohelices grown by He+-FIBID with tailored dimensions will be presented. Here, remarkable vortex and phase-slip phenomena have been found and explained by the corresponding numerical simulations [3]. In summary, a better understanding of nano-superconductivity is expected to occur in W-C nanostructures grown by the He+-FIBID technique. |
Monday, March 2, 2020 1:03PM - 1:15PM |
B48.00010: Magnetotransport properties of layered quasi-one-dimensional superconductor Ta2PdS5 Enze Zhang, Jinhua Zhi, Yi-Chao Zou, Zefang Ye, Linfeng Ai, Jiacheng Shi, Ce Huang, Shanshan Liu, Ning Kang, Hongqi Xu, Wei Wang, Liang He, Jin Zou, Jinyu Liu, Zhiqiang Mao, Faxian Xiu Ternary Ta2PdS5 is a newly discovered low-dimensional superconductor with typical quasi one-dimensional chain structure, which has attracted a great deal of research attention owing to its intriguing physical properties. Here we report the systematic study of magnetotransport properties of Ta2PdS5 nanowires exfoliated from its bulk material. The superconducting critical field of system shows strong anisotropic behavior and violation of the Pauli limit when the magnetic field is along the b-axis. I-V measurements show a series of multiple voltage steps in transition to normal state and systematic hysteresis between the up and down sweeps, indicating a typical quasi-one dimensional nature in its superconductivity. Surprisingly, the nanowire undergoes a superconductor-metal transition with increasing perpendicular magnetic field. Upon approaching the zero-temperature quantum critical point, the system uncovers the signature of the quantum Griffiths singularity state arising from enhanced quenched disorders, where the dynamical critical exponent becomes diverging rather than being constant. |
Monday, March 2, 2020 1:15PM - 1:27PM |
B48.00011: Superconductivity at the LaAlO3/SrTiO3 1D Zigzag Nanowires Yun-Yi Pai, Megan Briggeman, Hyungwoo Lee, Jung-Woo Lee, Xiaoxing Cheng, Muqing Yu, Mengchen Huang, Jianan Li, Chang-Beom Eom, Long Q. Chen, Patrick Irvin, Jeremy Levy LaAlO3/SrTiO3 exhibits electron pairing far outside of the superconducting state [1]. The superconducting state of LaAlO3/SrTiO3 also exhibits an intrinsic 1D nature [2] which has been linked to ferroelastic domain structure in the SrTiO3. We further explore the role of ferroelastic domain patterns on superconductivity by creating a series of “zig-zag” nanowire structures. We find that straight nanowires are comparatively more resistive, both in their normal and superconducting state, than channels that have a zig-zag structure. We discuss possible interplay between the charge degree of freedom and the structural domains and employ state-of-the-art phase-field modeling to simulate the relevant domain morphologies. |
Monday, March 2, 2020 1:27PM - 1:39PM |
B48.00012: Frictional drag between two LaAlO3/SrTiO3 superconducting nanowires Yuhe Tang, Jung-Woo Lee, Anthony Tylan-Tyler, Hyungwoo Lee, Michelle Tomczyk, Mengchen Huang, Chang-Beom Eom, Patrick Irvin, Jeremy Levy We report frictional drag measurements between two superconducting LaAlO3/SrTiO3 nanowires. In these experiments, current passing through one nanowire induces a voltage across a nearby electrically isolated nanowire. The frictional drag signal contains both symmetric and antisymmetric components. The antisymmetric component arises from the rectification of quantum shot noise in the drive wire due to asymmetries in the drag wire. The symmetric component is ascribed to rectification of thermal noise in the drive wire during superconducting-normal transition. The absence of symmetric drag resistance between a normal drag wire and a superconducting drive wire suggests a higher electron-hole asymmetry in the superconducting LaAlO3/SrTiO3 nanowire arising from the 1D nature of superconductivity at LaAlO3/SrTiO3 interface. |
Monday, March 2, 2020 1:39PM - 1:51PM |
B48.00013: Interface superconductivity in La2-xSrxCuO4 heterostructures Wenjie Gong, Larissa Little, Jason Hoffman, Jennifer E. Hoffman The lossless flow of current and the high, stable magnetic fields permitted by superconductor technology have led to advances in fields ranging from transportation to medical imaging. However, the low Tc of conventional superconductors—often below 30 K— has limited their commercial applicability. Previous work has demonstrated high-Tc superconductivity at interfaces between thin films of non-superconducting materials, such as between insulating and metallic La2-xSrxCuO4 [1]. Here, we aim to grow high-quality heterostructures of underdoped and overdoped La2-xSrxCuO4 on SrTiO3 and LaSrAlO4 with atomic layer-by-layer molecular beam epitaxy (MBE). We assess the samples grown with atomic force microscopy (AFM) and high-resolution x-ray diffraction (HRXRD). We then perform transport measurements on the La2-xSrxCuO4 heterostructures to examine the possible mechanisms behind Tc enhancement at atomic interfaces. |
|
B48.00014: Microscopic theory of in-plane critical field in two-dimensional Ising superconducting systems Hongchao Liu, Haiwen Liu, Ding Zhang, Xincheng Xie We study the in-plane critical magnetic field of two-dimensional Ising superconducting systems, and propose the microscopic theory for these systems with or without inversion symmetry. Protected by certain specific spin-orbit interaction which polarizes the electron spin to the out-of-plane direction, the in-plane critical fields largely surpass the Pauli limit and show remarkable upturn in the zero temperature limit. The impurity scattering and Rashba spin-orbit coupling, treated on equal-footing in the microscopic framework, both weaken the critical field but in qualitatively different manners. The microscopic theory is consistent with recent experimental results in stanene and Pb superconducting ultra-thin films. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700