Superfluidity of "dirty" indirect magnetoexcitons in coupled quantum wells in high magnetic field

TL;DR

This paper investigates how disorder and high magnetic fields affect superfluidity of indirect magnetoexcitons in coupled quantum wells, revealing suppression effects on superfluid density and transition temperature.

Contribution

It introduces a model reducing the complex system to an effective exciton problem, analyzing the impact of magnetic field and disorder on superfluid properties.

Findings

Increasing magnetic field and interwell distance suppress superfluid density.

Disorder can eliminate superfluidity at high magnetic fields.

Superfluid transition temperature decreases with stronger disorder and magnetic field.

Abstract

Superfluidity in the quasi-two-dimensional (2D) system of spatially indirect magnetoexcitons in coupled quantum wells (CQW) and unbalanced two-layer electron system in high magnetic field $H$ is considered in the presence of a random field. The problem of the rare gas of magnetoexcitons with dipole-dipole repulsion in a random field has been reduced to the problem of the rare gas of dipole excitons without magnetic field with the effective magnetic mass of a magnetoexciton, which is a function of the magnetic field and parameters of the CQW, in an $H$-dependent effective random field. The density of the superfluid component $n_{s}$ and the temperature $T_{c}$ of the Kosterlitz-Thouless transition to a superfluid state are obtained as functions of magnetic field $H$, interlayer separation $D$ and the random field parameters $\alpha_{i}$ and $g_{i}$. For 2D magnetoexcitonic systems, the rise of the magnetic field $H$ and the interwell distance $D$ is found to increase the effective renormalized random field parameter $Q$ and suppress the superfluid density $n_s$ and the temperature of the Kosterlitz-Thouless transition $T_c$. The suppressing influence of $D$ on $n_s$ and $T_c$ in strong magnetic filed is opposite to the case without magnetic field, when $n_s$ and $T_c$ increase with the rise of $D$ at fixed total exciton density $n$. It is shown that in the presence of the disorder at sufficiently large magnetic field $H$ or parameters of the disorder there is no superfluidity at any exciton density.