Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D48: Superconductivity: Transport Properties |
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Sponsoring Units: DCMP Chair: Michael Osofsky, United States Naval Research Laboratory Room: Mile High Ballroom 1A |
Monday, March 2, 2020 2:30PM - 2:42PM |
D48.00001: Analysis of thermal conductivity for pairing symmetry in high-Tc cuprate superconductors H.-T. Kim, Minguen Choi The pairing symmetry of high-Tc cuprate superconductors has been unsolved over 30 years. Most researchers have believed that the pairing symmetry is dx2-y2 (d) wave, nevertheless, several objections have been still suggested. Recently the objection was also disclosed [1]. We reanalyze the data of thermal conductivity, κ, announced as experimental evidence of d-wave symmetry, which showed the presence of a finite value at nearest T=0 K in a curve of κ/T vs T2 in thermal conductivity [2]. This is the metal characteristic coming from the nodes of the d-wave electronic structure of clover [2]. The characteristic of the curve of κ/T vs T2 increases a residual linear value of κ/T with going to T=0 K, which does not describe the pairing symmetry characteristic of κ. We redrew the curve of κ/T vs T2 to the curve of κ vs T, deduced experimental data below 0.2 K unobservable by experiment through polynomial fitting, and discovered the behavior of the conductivity with nonlinear and no residual linear value. This is evidence denying d-wave symmetry, rather, supports s-wave symmetry. [1] arXiv:1710.07754. [2] M. Sutherland et al., Phys, Rev. B 67, 174520 (2003). |
Monday, March 2, 2020 2:42PM - 2:54PM |
D48.00002: DC Hall measurements in the strongly correlated Hubbard model Wen Wang, Jixun Ding, Brian Moritz, Edwin Huang, Thomas Devereaux We investigate the DC Hall conductivity, an indicator of charge carrier properties, of the single-band Hubbard model in the zero field limit[1] using determinant quantum Monte Carlo (DQMC). Utilizing an effective expansion to lowest order, we observe a change of sign in the Hall coefficient as a function of temperature and interaction strength, which may signal a change in the topology of the Fermi surface. We relate the Hall coefficient to the frequency dependent resistivity, also obtained from DQMC following analytic continuation, to reveal the properties of charge carriers within the strange metal phase of the Hubbard model. |
Monday, March 2, 2020 2:54PM - 3:06PM |
D48.00003: Hall Conductivity in the Hubbard Model from Determinant Quantum Monte Carlo Jixun Ding, Wen Wang, Yoni Schattner, Brian Moritz, Edwin Huang, Thomas Devereaux We extend determinant quantum monte carlo (DQMC) to allow for the addition of a constant magnetic field to the usual Hubbard model hamiltonian. We calculate the frequency and field dependent electrical Hall conductance for the single-band Hubbard model on a two-dimensional square lattice as a function of doping and temperature. Limiting cases of our results are compared with both those from recent experiments and an alternative theoretical technique. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D48.00004: Resistance oscillations in the quantum metal phase of lithium intercalated TiSe2 Menghan Liao, Heng Wang, Yuying Zhu, Mohsin Rafique, Xiang Xu, Lexian Yang, Ding Zhang, Qikun Xue The nature of the metallic ground state, in the transition from a superconductor to an insulator at a temperature close to absolute zero, is still a mystery. In this work, we uncover quantum oscillations of this quantum metal or failed superconductor in a three-dimensional anisotropic superconductor—lithium intercalated TiSe2. The quantum metallic state, hosting saturating resistance below the superconducting transition even after properly filtering of radio-frequency (RF) signals, depends sensitively on the lithium doping. Exactly in this metallic regime, we show that the resistance oscillates as a function of magnetic field with a period that changes gradually with temperature. We attribute this oscillation to flux effects imposed by the domains of a coexisting charge density wave (CDW). It suggests that a periodically perturbed superconductor, either by CDW or artificial patterning, may be key to realizing the quantum metal. |
Monday, March 2, 2020 3:18PM - 3:30PM |
D48.00005: Transport properties of EuTiO3-δ down to 50 mK Jiaming He, Jianshi Zhou Tetravalent perovskite titanates garnered great attention due to its unique dielectric properties. Within the family, the electron-doped SrTiO3 was found to be superconducting below 1 K; its superconducting transition temperature has a dome-shaped dependence with carrier concentration [1]. Low temperature transport properties of electron-doped SrTiO3 can be described by Fermi liquid theory [2]. Cubic perovskite EuTiO3 has identical Ti-O subarray as SrTiO3. However, interaction between mobile electron spins and magnetic moments in Eu3+ may dramatically change transport properties. So far, transport properties of EuTiO3 at sub Kelvin temperatures have not been studied. We obtained high quality single crystal EuTiO3 by floating zone method; oxygen deficiency is introduced by annealing the crystal at different temperatures. These samples are characterized by suite of measurements including resistivity, specific heat capacity, and Seebeck coefficient. The electron doping converts the crystal from semiconductor to metal. As revealed by the resistivity and the specific heat, EuTiO3-δ exhibits filamentary superconductivity at 1.4 K. |
Monday, March 2, 2020 3:30PM - 3:42PM |
D48.00006: Electronic phase diagram of Ta1-xMoxS2 and optimization of superconductivity in a charge density wave system Jose Salcedo- Pimienta, Juan Mendoza Arenas, Jose Galvis Echeverry, Ian Fisher, Luis Quiroga, Ferney Rodriguez, Paula Giraldo-Gallo Transition metal dichalcogenides are a family of quasi-2-dimensional quantum materials with a unique susceptibility to the variation of parameters such as pressure, chemical doping, disorder, etc. These materials have been extensively studied due to the wide variety of electronic ground states they can show. Of special interest are the compounds of this family that show charge density wave (CDW) ordering and superconductivity, since the exact mechanism for the stabilization and optimization of superconductivity in systems that show these two ground states is still an open question. In this talk we present experimental transport results in single crystals of the solid solution Ta1-xMoxS2. We observe a suppression of the CDW transition temperature with increasing Mo content, accompanied by a strong enhancement of the superconducting transition temperature. We discuss our results in the context of the evolution of the electronic and structural properties of this solid solution as we approach the MoS2 compound, and their relationship to the possible existence of a CDW quantum critical point. |
Monday, March 2, 2020 3:42PM - 3:54PM |
D48.00007: Thermoelectric Effects in Superconductor-Ferromagnetic Heterostructures Kirsten Blagg, Portia Allen, Bradley Lloyd, Michael P Lilly, Meenakshi Singh Superconductor-ferromagnetic (S-F) heterostructures have been predicted to show large thermoelectric effects at cryogenic temperatures with a figure of merit of ~1.8. Confirmation of these theoretical predictions requires S-F heterostructures, controlled temperature gradients, cryogenic thermometry, thermal conductivity measurements, and electrical transport measurements. To this end, we have developed an experimental platform for the measurements of thermal and electrical transport in nanoscale devices at cryogenic temperatures. S-F heterostructures have been fabricated using lithography, evaporation, and sputtering, providing precise control over interfaces, and a wide choice of materials and geometries. Heaters and resistive thermometers, patterned via focused ion beam assisted platinum deposition, have been calibrated and optimized for thermal transport measurements at cryogenic temperatures. Finally, the Seebeck coefficient of S-F heterostructures has been measured in the presence of a magnetic field. This measurement sets the stage for systematic examination of the effects of dimensionality, ferromagnet polarization, and interface quality. |
Monday, March 2, 2020 3:54PM - 4:06PM |
D48.00008: Thermal Transport as a Probe of the Hidden Rashba Effect in the High Temperature Superconductor YBa2Cu3O6+x Bill Atkinson, Arno P Kampf The high temperature superconductor YBa2Cu3O6+x is an example of a Rashba bilayer material. The crystal structure comprises a stack of CuO2 bilayers, and while each bilayer is inversion symmetric, the individal CuO2 planes within the bilayers are not. This leads to a so-called hidden spin polarization, in which each layer making up the bilayer has a Rashba coupling constant with opposite sign such that the net spin polarization vanishes. In this talk, I will discuss the origins of the effect in YBa2Cu3O6+x, and show that the measurement of the transverse thermal conductivity in an in-plane magnetic field allows one to make a sensitive measurement of the Rashba coupling. |
Monday, March 2, 2020 4:06PM - 4:18PM |
D48.00009: Giant Edelstein effect in the surface states of non-centrosymmetric superconductors Yuhei Ikeda, Youichi Yanase It is an important topic in the modern field of spintronics to control magnetic moments by using local electric current. One of the representative methods is the Edelstein effect [1]. However, for practical applications, e.g. magnetic domain switching [2], it is widely known that quite a large amount of electric current density is needed. Therefore, Joule heating created by a dissipative current is the main obstacle for efficient control of magnetization. |
Monday, March 2, 2020 4:18PM - 4:30PM |
D48.00010: Effect of Zeeman Splitting on Andreev Reflection in Quantum Hall--Superconductor Heterostructures Joseph Cuozzo, Xiang Hu, Stuart N Thomas, Enrico Rossi We study the effect of Zeeman splitting on Andreev processes and non-local transport in heterostructures formed by two-dimensional systems in the superconducting and integer quantum Hall regime. We obtain analytic expressions for the dependence of the Andreev reflection probabilities on the Zeeman splitting in the narrow-contact and long-contact limits using an low-energy effective edge-state Hamiltonian within the Bogoliubov de-Gennes formalism. We find that introducing a higher-order, spin-dependent contribution to the renormalized drift velocity in the effective model is important to obtain accurate results. We then correlate the scattering wave function's penetration into the superconducting region with the observed Andreev reflection probabilities. |
Monday, March 2, 2020 4:30PM - 4:42PM |
D48.00011: Manifestations of spin-orbit coupling in a cuprate superconductor Zachary Raines, Andrew A Allocca, Victor Galitski Exciting new work on Bi2212 shows the presence of non-trivial spin-orbit coupling effects as seen in spin resolved ARPES data [Gotlieb et al., Science, 362, 1271-1275 (2018)]. |
Monday, March 2, 2020 4:42PM - 4:54PM |
D48.00012: A cyclic superconducting quantum refrigerator for adiabatic magnetization cooling Sreenath Kizhakkumpurath Manikandan, Francesco Giazotto, Andrew N Jordan We propose a solid-state refrigeration technique using adiabatic magnetization/ demagnetization cycles of a superconductor, acting as the working substance. The gradual cooling down of a substrate (normal metal) in contact with the working substance is predicted, where the excess heat is given to a hot, large-gap superconductor. The selective cooling of the normal metal is due to an effective thermal switching mechanism owing to the asymmetry of heat transport between N/N versus N/S junctions. We predict cooling of a 0.3cm^3 block of Cu by almost two orders of magnitude starting from 200mK, and down to about 1mK starting from the base temperature of a dilution fridge (10mK). The cooling powers at 200mK and 10mK for a 1cmx1cm interface are 25 nW and 0.06 nW respectively, which scales with the area of the interface. |
Monday, March 2, 2020 4:54PM - 5:06PM |
D48.00013: Parity dependent supercurrent amplitude and phase of InSb/Al hybridized island Jiyin Wang, Constantin Schrade, Vukan Levajac, David van Driel, Sasa Gazibegovic, Roy Op het Veld, Kongyi Li, Joon Sue Lee, Mihir Pendharkar, connor dempsey, Chris J Palmstrom, Erik Bakkers, Liang Fu, Leo P Kouwenhoven, Jie Shen Semiconductor nanowires coupled with superconductors are a promising platform to construct Majorana zero modes as well as to build up topological fault-tolerant quantum computers. In semiconductor nanowire/superconductor hybridized island, charging energies are introduced and thus even/odd parity of two Majorana zero modes exhibit as a two-level quantum system, which could work as topological qubits. By embedding such hybridized islands into superconducting circuit, not only can trivial Andreev bound states and Majorana bound states be distinguished via the supercurrent phase of the island, but also topological-qubit readout and operation can be performed by supercurrent measurement. Here, we insert an InSb/Al hybridized island into NbTiN superconducting circuit forming a superconducting interference device (SQUID). In such a device, we find switching current of the InSb/Al island depends on its parity and the corresponding superconducting phase also show parity-dependent behaviours. In this way, the parity of bound state residing in hybridized island can be read out, which paves the way for parity read out of Majorana superconducting qubits. |
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