Superfluidity of dipolar excitons in a double layer of $\alpha-T_3$ with a mass term

TL;DR

This paper predicts Bose-Einstein condensation and superfluidity of dipolar excitons in a gapped $ ext{GHAT}_3$ double layer, analyzing their properties and critical temperature considering the effects of a mass term and magnetic field.

Contribution

It introduces the concept of superfluidity of dipolar excitons in $ ext{GHAT}_3$ layers with a mass term, providing new insights into their collective excitations and critical temperature.

Findings

Calculated binding energies of A and B excitons.

Derived the dispersion relation and sound velocity of collective excitations.

Estimated the critical temperature for superfluidity.

Abstract

We predict Bose-Einstein condensation and superfluidity of dipolar excitons, formed by electron-hole pairs in spatially separated gapped hexagonal $\alpha-T_{3}$ (GHAT3) layers. In the $\alpha-T_{3}$ model, the AB-honeycomb lattice structure is supplemented with C atoms located at the centers of the hexagons in the lattice. We considered the $\alpha-T_{3}$ model in the presence of a mass term which opens a gap in the energy dispersive spectrum. The gap opening mass term, caused by a weak magnetic field, plays the role of Zeeman splitting at low magnetic fields for this pseudospin-1 system. The band structure of GHAT3 monolayers leads to the formation of two distinct types of excitons in the GHAT3 double layer. We consider two types of dipolar excitons in double-layer GHAT3: (a) ``A excitons'', which are bound states of electrons in the conduction band (CB) and holes in the intermediate band (IB) and (b) ``B excitons'', which are bound states of electrons in the CB and holes in the valence band (VB). The binding energy of A and B dipolar excitons is calculated. For a two-component weakly interacting Bose gas of dipolar excitons in a GHAT3 double layer, we obtain the energy dispersion of collective excitations, the sound velocity, the superfluid density, and the mean-field critical temperature $T_{c}$ for superfluidity.