Ground state and low-energy excitations of a quantum critical superconductor (Jan. 13, 2023)

  • Published: 2023-01-09

Time: 10:00 am, Jan. 13, 2023 (Friday)

Zoom URL:

Zoom ID: 893 3621 7023

Password: 123789


Speaker: Shang-Shun Zhang (University of Minnesota)



At a quantum critical point of a metal, the critical order parameter fluctuations become soft and mediate singular interactions between electrons, which are effectively described by a frequency-dependent function 1/Ω^?. The parameter ? depends on the specific microscopic models. This singular interaction gives rise to two competing tendencies towards either the non-Fermi liquid or superconducting state. In this talk, I show that the pairing of electrons wins the competition. The gap function strongly depends on the frequency and develops an array of dynamical vortices on the complex frequency plane. This array of vortices moves with the interaction parameter ? and crosses the real-frequency axis one by one, which gives rise to measurable effects such as a list of peaks in the density of states. Further, we show that the low-energy excitations above the superconducting ground state display a traditional BCS-like behavior at ?1/2, as revealed by both density of state and the spectral function.