Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L49: The Superconductor-Insulator Transition: Beyond Universal ScalingInvited Live
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Sponsoring Units: DCMP Chair: Norman Armitage, Johns Hopkins University |
Wednesday, March 17, 2021 8:00AM - 8:36AM Live |
L49.00001: New paradigm for a magnetic field driven SIT Invited Speaker: Nandini Trivedi We show that while orbital magnetic field and disorder, acting individually weaken superconductivity, acting together they produce an intriguing evolution of a two-dimensional type-II s-wave superconductor[1-4]. For weak disorder, the critical field at which the superfluid density collapses matches the field at which the superconducting energy gap gets suppressed to zero. With increasing disorder, these two fields diverge from each other creating a pseudogap region. We predict a transformation from "Abrikosov" metallic vortex cores for weak disorder to "Josephson" vortices with gapped and insulating cores for higher disorder. Our results explain the disappearance of the celebrated zero-bias Caroli-de Gennes-Matricon (CdGM) peak in experiments on disordered superconductors. The emergence of the pseudogap phase provides a natural understanding of the long standing puzzle of the gigantic magnetoresistance peak observed as a function of magnetic field in thin disordered superconducting films. |
Wednesday, March 17, 2021 8:36AM - 9:12AM Live |
L49.00002: Quasiparticle screening near a bosonic superconductor-insulator transition revealed by magnetic impurity doping Invited Speaker: James Valles
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Wednesday, March 17, 2021 9:12AM - 9:48AM Live |
L49.00003: The fate of the superfluid density near the SIT in amorphous superconductors Invited Speaker: Benjamin Sacepe Superconducting films of amorphous Indium Oxide (a:InO) thin films undergo a transition to insulation upon increasing disorder. This quantum phase transition is driven by the localization of preformation of Cooper pairs, which has been evidenced through various unusual spectroscopic properties. The continuous decrease of the critical temperature as the critical disorder approaches indicates a similarly continuous suppression of the superfluid density. In this talk I discuss the fate of the superfluid density in the vicinity of the transition to insulation in a:InO films. To access the superfluid density we conducted a systematic study of the whole plasmon dispersion spectrum of high quality factor microwave resonators made of a:InO, combined with DC resistivity measurements, as a function of disorder. Our main observations are a breakdown of the Mattis-Bardeen theory and a record kinetic inductance of 17nH per square for critical, superconducting samples. Surprisingly, we find that the superfluid density remains finite up to the critical disorder. Besides providing new insights to understand the SIT in a:InO, these results may find applications in superconducting quantum circuits where very large inductances are highly desirable. |
Wednesday, March 17, 2021 9:48AM - 10:24AM Live |
L49.00004: Absence of a Dissipative Quantum Phase Transition in Josephson Junctions Invited Speaker: Philippe Joyez In 1962 Josephson predicted that an electric current can flow with no applied voltage through a thin insulating layer separating two superconductors. Since then, this "Josephson junction" has taken the central role in quantum electronic devices (squids magnetometers, parametric amplifiers, superconducting qubits,…), among which, notably, the Josephson voltage standard which helped rebasing the International System of Units on quantum effects. |
Wednesday, March 17, 2021 10:24AM - 11:00AM Live |
L49.00005: Quantum electrodynamics of superconductor-insulator transitions in Josephson junction chains. Invited Speaker: Vladimir Manucharyan It is customary to associate a superconducting phase with zero resistance and an insulating phase with infinite resistance. However, experimentally measured resistance often does not attain either value, and quantum phase transition physics is hidden in the scaling of resistance with temperature, size, magnetic field, etc. Instead, we consider the finite frequency spectroscopy of the collective phase-mode at excitation levels far below a single quantum. In this case, the superconducting phase manifests itself through a non-zero phase-stiffness, while the insulating phase results in the damping of the phase-mode by quantum phase-slip fluctuations. The damping of the phase-mode is independent of the system’s size, but scales with the frequency, which is a more reliable scaling parameter than temperature. We present the recent results of our spectroscopic studies on three notable SIT systems: a high-inductance ring interrupted by a weak junction (quasicharge localization) [1]; (ii) a homogeneous chain of Josephson junctions (1D superfluid to Bose-glass insulator transition) [2]; and (iii) a chain of relatively strong junctions containing one weak junction impurity (Shmid-Bulgadaev dissipative transition). |
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