Specific Heat of a Quantum Critical Metal

TL;DR

This study uses quantum Monte Carlo simulations to explore the specific heat behavior near an Ising nematic quantum critical point, revealing a regime where the specific heat remains band-structure-like before superconductivity sets in.

Contribution

It provides the first sign problem-free quantum Monte Carlo analysis of specific heat near a nematic QCP, highlighting the interplay between non-Fermi liquid behavior and superconductivity.

Findings

$c/T$ remains close to non-interacting values over a broad temperature range

Rapid increase of $c/T$ at lower temperatures indicating non-Fermi liquid behavior

Superconductivity onset coincides with the suppression of $c/T$ and spin susceptibility

Abstract

We investigate the specific heat, $c$, near an Ising nematic quantum critical point (QCP), using sign problem-free quantum Monte Carlo simulations. Cooling towards the QCP, we find a broad regime of temperature where $c/T$ is close to the value expected from the non-interacting band structure, even for a moderately large coupling strength. At lower temperature, we observe a rapid rise of $c/T$, followed by a drop to zero as the system becomes superconducting. The spin susceptibility begins to drop at roughly the same temperature where the enhancement of $c/T$ onsets, most likely due to the opening of a gap associated with superconducting fluctuations. These findings suggest that superconductivity and non-Fermi liquid behavior (manifested in an enhancement of the effective mass) onset at comparable energy scales. We support these conclusions with an analytical perturbative calculation.