Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session P48: Superconductivity: Transport Properties II |
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Sponsoring Units: DCMP Chair: Jose Vicent, Univ Complutense Room: Mile High Ballroom 1A |
Wednesday, March 4, 2020 2:30PM - 2:42PM |
P48.00001: Study on the pressure-induced superconducting phases of antimony Zheng Wu, Liangzi Deng, Melissa Gooch, Shuyuan Huyan, Paul C. W. Chu Pressure-induced superconductivity in antimony was investigated electrically using a diamond anvil cell up to 61 GPa. A semimetal to metal transition was observed in the pressure range of 22 to 28 GPa at room temperature, which coincides with the transition from an incommensurate tetragonal host-guest structure to a body-centered cubic (bcc) structure. The high pressure metal phase was found to be superconducting and the transition temperature (Tc) was non-monotonous with regard to the applied pressure while in the bcc structure. The empirical rule, lighter elements having higher Tcs in a homologous series in non-transition elements in the periodic table, was found not to hold for bcc Sb when compared with Bi. A controlled pressure quench of the superconducting phase in the incommensurate composite phases at temperatures up to 77 K was also performed and the zero resistance was retained in the quenched phase with the midpoint of the superconducting transition above 3.4 K and a transition width of 0.2 K. |
Wednesday, March 4, 2020 2:42PM - 2:54PM |
P48.00002: Andreev quantum dot chain in an InSb nanowire Hao Wu, Po Zhang, Jun Chen, Sasa Gazibegovic, Roy Op het Veld, Ghada Badawy, Erik Bakkers, Sergey M Frolov We built a chain of quantum dots in a semiconductor nanowire to study the Kitaev model of a one dimensional topological superconductor. Three quantum dots are electrostatically confined in an InSb nanowire. Each dot is strongly coupled to a superconducting NbTiN electrode. We observe Andreev bound states in each of these quantum dots and study their magnetic field dependence with fields parallel to the nanowire axis. Having two normal contacts at the wire ends and three superconducting leads, we are able to perform non-local measurements. We study spatial separation of Andreev bound states in this three dots chain with various inter-dot coupling strengths. Our experiments may provide insights on non-locality of zero modes in Majorana wires. |
Wednesday, March 4, 2020 2:54PM - 3:06PM |
P48.00003: Quantum Hall Effect in an Epitaxial Nitride Semiconductor/Superconductor Heterostructure Phillip Dang, Guru Bahadur Khalsa, D. Scott Katzer, Neeraj Nepal, Brian Downey, Virginia D. Wheeler, Alexey Suslov, Andy Xie, Edward Beam, Yu Cao, Cathy Lee, Huili Xing, David Meyer, Debdeep Jena The quantum Hall effect (QHE) is a paragon of topological protection in electronic states, exhibiting exceptional precision in resistance, while superconductivity allows exceptional precision in voltage due to flux quantization. To create seamless heterostructures of these two electronic phases is highly desirable for the discovery of new physics and use in quantum information science. To this end, we design an all-epitaxial superconductor/semiconductor nitride heterostructure, based on GaN two-dimensional electron gases (2DEGs) and superconducting NbN, using an industrial device process that is compatible with silicon and nitride semiconductor technology. The heterostructure is demonstrated to simultaneously exhibit the integer QHE in the GaN 2DEG and superconductivity in the NbN. Such a demonstration in an all-epitaxial nitride heterostructure is the first of its kind and paves the way for new quantum technologies. |
Wednesday, March 4, 2020 3:06PM - 3:18PM |
P48.00004: Transport properties of double quantum dots coupled to a superconductor Po Zhang, Hao Wu, Sabbir Ahmed Khan, Peter Krogstrup, David Pekker, Sergey M Frolov Superconductor/semiconductor hybrid systems have drawn a lot of attention due to their rich physics and the potential to demonstrate topologically protected qubits. We experimentally investigate transport properties of a double dot electrostatically defined in an InAs nanowire by metallic gates under the wire. Superconductivity is provided by epitaxial Al shell grown in-situ after nanowire growth. The shell induces a hard gap and sharp spectral features of Andreev bound states in the nanowire. The source of the double dot is a normal metal while the drain is a superconductor. We study the spectra of the resulting normal-Andreev double dot and search for the recently proposed Andreev blockade upon which current is blocked in the triplet (1,1) configuration which is unable to form a Cooper pair and enter the drain superconductor. |
Wednesday, March 4, 2020 3:18PM - 3:30PM |
P48.00005: Angular dependence of the magnetoresistance in HgBa2CuO4+δ Katherine Schreiber, Eric Bauer, Neil Harrison, Mun Keat Chan The Fermi surface in the cuprates is known to undergo significant changes with temperature and doping, from Fermi arcs to small pockets reconstructed by charge density wave order. In general the shape of the Fermi surface for a particular phase reveals information about its place in the phase diagram; for example, the symmetries broken by the charge density wave. Such information is valuable to understanding the relationship of these phases to high temperature superconductivity. The pseudogap phase is of particular interest because superconductivity and the charge density wave emerge from this phase as temperature is lowered. |
Wednesday, March 4, 2020 3:30PM - 3:42PM |
P48.00006: Hall effect measurements under high pressure for Pr2Ba4Cu7O15-δ supercondcutor Fumihiro Ishikawa, Masaya Sawada, Ayako Ohmura, Takashi Naka, Antheunis de Visser It is well known that the Pr-substitution for Y-site in YBa2Cu3O7-δ and YBa2Cu4O8 dramatically suppresses the superconducting transition temperature Tc and superconductivity in CuO2 planes disappears. However, Pr2Ba4Cu7O15-δ (Pr247) oxide shows superconductivity with Tc = 15 K after reduction treatment [1]. Pr247 has the same crystal structure as Y2Ba4Cu7O15-δ with an alternative repetition of the single and double chains along the c-axis. As-sintered sample of Pr247 shows metallic conductivity at low temperatures owing to the conduction in the CuO double chains. Reduction treatment on Pr247 caused the electron carrier density change by controlling the amount of oxygen deficiency. Applying high pressure on superconductive Pr247 suppresses the superconductivity. This is well explained by the one-dimensional conduction mechanism based on Tomonaga-Luttinger liquid theory [2]. High pressure study on Hall effect reveals the effect of pressure on electron carrier concentration for Pr247. |
Wednesday, March 4, 2020 3:42PM - 3:54PM |
P48.00007: Influence of plastic deformation on the transport and magnetic properties of strontium titanate Sajna Hameed, Damjan Pelc, Zachary Anderson, Chris Leighton, Martin Greven Strontium titanate (SrTiO3, STO) is one of the most important transition metal oxides: it is a model perovskite with a structural phase transition, and also one of the most commonly used single crystal substrates for epitaxial growth of oxide thin films. Superconductivity in STO occurs at unusually low carrier densities at temperatures well below 1 K and is not understood, even five decades after its discovery. Building on our recent work on oxide superconductors [1], we explore another interesting property of STO: its high ductility at room temperature, which allows us to plastically deform single crystals using uniaxial pressure. We report on the influence of this compressive plastic deformation on the transport and magnetic properties of STO, with particular emphasis on the superconducting state. |
Wednesday, March 4, 2020 3:54PM - 4:06PM |
P48.00008: Anomalous transverse magnetoresistance in superconductor/ferromagnet multilayers Xavier Palermo, Salvatore Mesoraca, Nicolas Reyren, Anke Sander, Sophie Collin, Florian Godel, Karim Bouzehouane, Jacobo Santamaria, Vincent Cros, Alexandre Buzdin, Javier Villegas We have studied the magnetoresistance of metallic multilayers composed of a low-Tc superconductor (MoSi) and different ferromagnets (from single Co layers to combinations of these with heavy-elements) which present variable magnetic anisotropy and domain structure. In some cases, the longitudinal magnetoresistance shows a strong magnetic hysteresis that results from the interaction of flux quanta in the superconductor and the stray field from the ferromagnet's domains. Interestingly, that behavior is accompanied by an anomalous transverse magnetoresistance whose parity depends on the direction of the magnetic field relative to the ferromagnet's easy axis. We will discuss the different scenarios allowing for an understanding of these effects. |
Wednesday, March 4, 2020 4:06PM - 4:18PM |
P48.00009: Higgs mode and tr-ARPES in Non-equilibrium Superconductors with a Moving Condensate Ankit Kumar, Alexander F Kemper When a superconducting state is perturbed, one of the resulting excitations gives rise to the amplitude oscillation mode known as the Higgs mode. The existence of the Higgs mode in a perturbed broken-symmetry state is one of the fundamental phenomena in condensed matter systems. However, the Higgs mode is hard to measure experimentally due to the spin-less and charge-less nature of the condensate. Recently, it was proposed that the Higgs mode in superconductors can be coupled to light in the linear regime if there is a non-zero supercurrent present in the system. Motivated by that, we study the dynamics of the Higgs mode in the presence of supercurrent. We find that the supercurrent creates an asymmetry of the electron distribution in the momentum space which leads to a momentum-dependent superconducting spectral gap. When we pump the system with an ultra-fast light pulse, the frequency of the Higgs mode gains momentum dependence. We analyze the dynamics of the Higgs mode through the electron spectral function which can be measured using angle-resolved photoemission spectroscopy (ARPES), and propose that the presence of supercurrent may help in the observation of the Higgs mode through time-resolved ARPES. |
Wednesday, March 4, 2020 4:18PM - 4:30PM |
P48.00010: Magnetoconductance of planar cuprate superconductor/graphene junctions Kevin Seurre, Vincent Humbert, David Perconte, Christian Ulysse, Anke Sander, Juan Trastoy Quintela, Bruno Dlubak, Pierre Seneor, Javier Villegas Graphene/superconductor junctions have been extensively studied using low-Tc superconductors, but studies involving high-Tc temperature cuprates are scarce despite their interest for instance the rich physics expected from the d-wave order parameter. Here we study planar high-Tc superconductor/graphene junctions fabricated by transferring CVD graphene onto optimally doped c-axis PDL grown YBaCuO7-x films, which are patterned using electron lithography and ion irradiation. Transport measurements at low temperature revealed an interesting, anomalous behavior of the magnetoconductance, which first increases at low magnetic fields before remaining constant or decreasing depending on the samples. This effect highly depends on temperature and voltage bias applied to the junction. We will discuss the different scenarios allowing for an understanding of this behavior. |
Wednesday, March 4, 2020 4:30PM - 4:42PM |
P48.00011: Non-Majorana quantized zero-bias conductance peaks in semiconductor nanowire devices Maksim Gomanko, Peng Yu, Ghada Badawy, Sasa Gazibegovic, Roy Op het Veld, Erik Bakkers, Jun Chen, Sergey M Frolov Quantized zero bias conductance peaks are predicted and reported in InSb nanowire devices coupled to NbTiN superconductors under certain conditions that are compatible with Majorana zero modes. These conditions include induced superconductivity, spin-orbital coupling, and an external magnetic field. We observed quantized zero bias conductance peaks at one end of similar nanowire devices, without observing matching zero bias peak of any height on the other side. These results imply either a topological segment shorter than the superconducting segment which is 400 nm, or a non-Majorana origin of the observed quantized zero-bias peaks. |
Wednesday, March 4, 2020 4:42PM - 4:54PM |
P48.00012: Versatile and selective platform for high-quality hybrid semiconductor-superconductor nanowire devices. Nick Loo, Greg P. Mazur, Sebastian Heedt, Marina Quintero Perez, Francesco Borsoi, Alexandra Fursina, May An van de Poll, Kevin Van Hoogdalem, Ghada Badawy, Sasa Gazibegovic, Erik Bakkers, Leo P. Kouwenhoven Majorana bound states and topological superconductivity are highly anticipated candidates for decoherence-free quantum computation. To achieve this goal, high-quality semiconductor-superconductor hybrid systems are the most promising platform. Here, we combine high-mobility semiconductor nanowires with selective deposition of a superconducting material, resulting in state-of-the-art hybrid devices. We benchmark our devices by investigating InSb/Al Josephson junctions. In voltage-bias spectroscopy, we observe multiple Andreev reflections indicating a highly-transparent interface. Furthermore, in current-bias spectroscopy we observe remarkably high critical currents. Finally, we emphasize that we have developed a versatile platform which can easily be used to investigate different material combinations. In addition, it can be used to create sophisticated quantum circuits for the purpose of demonstrating the proof of principle of a topological qubit. |
Wednesday, March 4, 2020 4:54PM - 5:06PM |
P48.00013: Design and discovery of CaKRu4P4: a new member of the generalized 1144 structure. Mingyu Xu, Palasyuk Andriy, Sergey L. Bud'ko, Boqun Song, Kai-Ming Ho, Paul C Canfield AeAFe4As4 (Ae=Ca, Sr; A=K, Rb, Cs) compounds were discovered as a new structural type [1] which has alternate stacking of the Ae and A layers. The AeAFe4As4 structure is stabilized by the combination of large Δc (= cA122-cAe122) and small Δa (= aA122-aAe122), where a and c are lattice parameters of the AFe2As2 and AeFe2As2 parent structures. In this presentation we extent this idea to similar, phosphorus-based 122 compounds with large Δc and small Δa values, identifying CaKRu4P4 as a promising candidate. The stability of a CaK1144 type ruthenium phosphide was also recently predicted by combining first principle calculations [2]. We synthesize polycrystalline CaKRu4P4 by solid state reaction of CaRu2P2 and KRu2P2. The crystallographic structure and physical properties of CaKRu4P4 will be presented. |
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