Drag effect and Cooper electron-hole pair fluctuations in a topological insulator film

TL;DR

This paper investigates the fluctuation-induced drag effect in topological insulator films caused by Cooper electron-hole pairs, highlighting the dominant Aslamazov-Larkin contribution near the critical temperature and developing a macroscopic theoretical framework.

Contribution

It introduces a macroscopic theory based on the time-dependent Ginzburg-Landau equation to describe fluctuation effects in electron-hole bilayers, emphasizing the role of Cooper pair fluctuations in Coulomb drag.

Findings

Aslamazov-Larkin contribution diverges as (T - T_d)^{-1} near critical temperature.

Fluctuational effects can dominate transport when scattering rate is comparable to T_d.

The developed theory can be generalized to other electron-hole bilayer systems.

Abstract

Manifestations of fluctuating Cooper pairs formed by electrons and holes populating opposite surfaces of a topological insulator film in the Coulomb drag effect are considered. Fluctuational Aslamazov-Larkin contribution to the transresistance between surfaces of the film is calculated. The contribution is the most singular one in the vicinity of critical temperature $T_\mathrm{d}$ and diverges in the critical manner as $(T-T_\mathrm{d})^{-1}$. In the realistic conditions $\gamma\sim T_\mathrm{d}$, where $\gamma$ is average scattering rate of electrons and holes, Aslamazov-Larkin contribution plays important role and can dominate the fluctuation transport. The macroscopic theory based on time-dependent Ginzburg-Landau equation is developed for description of the fluctuational drag effect in the system. The results can be easily generalized for other realizations of electron-hole bilayer.