Superfluid weight cross-over and critical temperature enhancement in singular flat bands

TL;DR

This paper investigates how singular flat bands influence superfluid weight and critical temperature in 2D superconductors, revealing a tunable mechanism for enhancing supercurrent and transition temperature through band gap manipulation.

Contribution

It introduces a detailed analysis of superfluid weight behavior near singular flat bands and demonstrates how tuning the band gap can enhance superconducting properties.

Findings

Superfluid weight exhibits crossover behavior at band gap closure.

Tuning the singular band gap can enhance the supercurrent.

Critical temperature can be increased via band gap control.

Abstract

Non-analytic Bloch eigenstates at isolated band degeneracy points exhibit singular behavior in the quantum metric. Here, a description of superfluid weight for zero-energy flat bands in proximity to other high-energy bands is presented, where they together form a singular band gap system. When the singular band gap closes, the geometric and conventional contributions to the superfluid weight as a function of the superconducting gap exhibit different crossover behaviors. The scaling behavior of superfluid weight with the band gap is studied in detail, and the effect on the Berezinskii-KosterlitzThouless (BKT) transition temperature is explored. It is discovered that tuning the singular band gap provides a unique mechanism for enhancing the supercurrent and critical temperature of two-dimensional (2D) superconductors.