Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W45: Superconductivity in Non-Fermi LiquidsInvited Live Streamed
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Philip Phillips, University of Illinois at Urbana-Champai Room: McCormick Place W-375D |
Thursday, March 17, 2022 3:00PM - 3:36PM |
W45.00001: Superconductivity out of a Non-Fermi Liquid Invited Speaker: Andrey V Chubukov In this talk I will discuss the interplay between non-Fermi liquid behavior and pairing near a quantum-critical point (QCP) in a metal. These tendencies are intertwined in the sense that both originate from the same interaction mediated by gapless fluctuations of a critical order parameter. The two tendencies compete because fermionic incoherence destroys the Cooper logarithm, while the pairing eliminates scattering at low energies and restores fermionic coherence. I will discuss this physics for a class of models with an effective dynamical interaction V (W) ~1/|W|γ (the γ-model). This model describes, in particular, the pairing at a 2D Ising-nematic critical point in (γ=1/3), a 2D antiferromagnetic critical point (γ=1/2) and the pairing by an Einstein phonon with vanishing dressed Debye frequency (γ=2). I will argue that the pairing wins, unless the pairing component of the interaction is artificially reduced, but because of fermionic incoherence in the normal state, the pairing problem is fundamentally different from BCS/Eliashberg one. I will show that a system develops pseudogap behaviour in the temperature range between the onset of the pairing at Tp and the onset of phase coherence at the actual superconducting Tc. The ratio Tc/Tp decreases with γ and vanishes at γ =2. I will present two complementary arguments of why this happens. One is the softening of longitudinal gap fluctuations, which become gapless at γ =2. Another is the emergence of a 1D array of dynamical vortices, whose number diverges at γ =2. I will argue that a fundamentally novel superconducting ground state emerges at γ >2, with a macroscopically degenerate bound state at the onset of the continuum. Overall, I will argue that γ=2 is a critical point of a dynamical topological transition and discuss topological distinction between superconductivity at γ<2 and γ>2. I will present and discuss a generic phase diagram. |
Thursday, March 17, 2022 3:36PM - 4:12PM |
W45.00002: Cooper pairing without quasiparticles Invited Speaker: Ilya Esterlis Superconductivity is the ultimate fate of a Fermi liquid at low temperatures. More broadly, superconductivity occurs in many systems where sharp Fermi liquid quasiparticles are absent and the nature of pairing in such incoherent systems thus raises an important problem. I will present work on a natural generalization of the Sachdev-Ye-Kitaev model to systems of interacting electrons and bosons, which demonstrates that both critical and fully incoherent electrons still undergo a superconducting transition. I will describe various properties of the resulting state, such as the possibility of a strongly coupled fluid of Cooper pairs below Tc. I will also describe pair breaking effects due to time-reversal symmetry breaking, leading to a theory that may be understood as a non-Fermi liquid counterpart of the Abrikosov-Gor'kov pair breaking theory by paramagnetic impurities in superconductors. |
Thursday, March 17, 2022 4:12PM - 4:48PM |
W45.00003: Exact theory for superconductivity in a doped Mott insulator Invited Speaker: Edwin Huang Because the cuprate superconductors are doped Mott insulators, it would be advantageous to solve even a toy model that exhibits both Mottness and superconductivity. In this talk, I consider the Hatsugai-Kohmoto model, an exactly solvable system that is a prototypical Mott insulator above a critical interaction strength at half filling. Upon doping or reducing the interaction strength, our exact calculations show that the system becomes a non-Fermi liquid metal with a superconducting instability. In the presence of a weak pairing interaction, the instability produces a thermal transition to a superconducting phase, which is distinct from the BCS state, as evidenced by a gap-to-transition temperature ratio exceeding the universal BCS limit. The elementary excitations of this superconductor are not Bogoliubov quasiparticles but rather superpositions of doublons and holons, composite excitations signaling that the superconducting ground state of the doped Mott insulator inherits the non-Fermi liquid character of the normal state. An unexpected feature of this model is that it exhibits a superconductivity-induced transfer of spectral weight from high to low energies as seen in the cuprates as well as a suppression of the superfluid density relative to that in BCS theory. |
Thursday, March 17, 2022 4:48PM - 5:24PM |
W45.00004: Solvable strong-coupling models for pairing and charge-4e superconductivity in non-Fermi liquids Invited Speaker: Yuxuan Wang We present Sachdev-Ye-Kitaev-like models that captures the interplay between fermionic incoherence and strong attractive interaction in the pairing instability of non-Fermi liquids. The first class of models feature random all-to-all interactions among fermions and bosons. We show that this model exhibits ``self-tuned quantum criticality" for a range of fermion filling independent on the bare boson mass. Unlike BCS instability, the pairing phase of electrons occur at T=0 only for some range of parameters, which is separated by the non-Fermi liquid phase via an infinite-order Kosterliz-Thouless critical point. In the second class of models, we consider a solvable Sachdev-Ye-Kitaev-like model for charge-4e superconductivity. We determine spectral properties, the superfluid density, and the pairing instability of a charge-4e superconductor, which applies even in the strong-coupling regime. |
Thursday, March 17, 2022 5:24PM - 6:00PM |
W45.00005: Strange metal transport and violation of the conjectured Planckian scattering rate limit in electron-doped cuprates Invited Speaker: Richard L Greene I will discuss recent transport studies of the electron-doped cuprate system La2-xCexCuO4 that exhibits strange metal transport in the normal state down to 35 mK. The strange metal behavior is manifested as a linear-in-T resistivity from 35 mK to 20K and a ~T^2 resistivity from 50K to 400K over a range of doping above and below a Fermi surface reconstruction at x = 0.14 [1-2]. Other strange metal behavior includes an anomalous low temperature linear-in-H magnetoresistance and lnT thermopower [3-5]. I also show that the magnitude of the ~T^2 resistivity far exceeds the conjectured Planckian bound on inelastic scattering [6]. |
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