Effect of thermal fluctuations on topological crossover in the chiral d+id superconducting phase

TL;DR

This study examines how thermal fluctuations influence the topological index in a chiral d+id superconductor, revealing conditions that expand or induce topological crossovers across temperature ranges.

Contribution

It introduces a self-consistent functional-integral approach to analyze thermal effects on topological properties in a two-dimensional superconducting model.

Findings

Thermal fluctuations extend the temperature range of stable topological indices.

Nodal point positions relative to the Fermi contour affect topological crossover behavior.

Thermal effects can induce persistent topological crossovers over wide temperature ranges.

Abstract

The effect of thermal fluctuations on the temperature dependence of the topological index C1 of the chiral d+id superconducting phase of a two-dimensional single-band model on a triangular lattice is investigated. Thermal fluctuations are taken into account within the framework of the self-consistent functional-integral theory. It is established that when the nodal points are located far inside (outside) the Fermi contour of the normal phase, thermal fluctuations expand the relative temperature ranges in which the values of the topological index are close to integer values C1=4(-2). This expansion depends both on the value of the topological index and on the magnitude of the effective attraction between the electrons. However, as the nodal points approach the Fermi contour, topological crossovers to new C1 values are observed, which can persist over a wide temperature range. The nature and degree of influence of thermal fluctuations on these crossovers are established. It is assumed that the observed effects may also manifest in the edge state behavior of a similar system with open boundaries.