Density of states and excitonic condensation in the double layer correlated systems

TL;DR

This paper investigates the density of states and excitonic condensation phenomena in strongly correlated double layer systems, revealing unique spectral features, phase crossover behaviors, and the coexistence of pair formation and condensation.

Contribution

It provides a detailed analysis of the spectral functions and density of states in double layer systems, highlighting the simultaneous occurrence of excitonic pair formation and condensation, and explores the effects of interlayer Coulomb interactions.

Findings

Spectral function collapse at high-symmetry points.

Double peak structures in DOS indicating condensates.

Evidence of hybridization gap at high temperatures.

Abstract

We consider the single-particle density of states (DOS) in the strongly correlated double layer (DL) system, without applied external fields. We demonstrate an unusual collapse effect in the spectrum of the normal single-particle spectral function at the particular high-symmetry point corresponding to the specific bunching-point solution of the chemical potential in the Frenkel channel. We show that at the low-temperature limit the anomalous spectral function obeys a concave like structure, which is directly related to the interlayer pair formation and condensation. We calculate the normal DOS functions, and we find their temperature dependence for different values of the interlayer Coulomb interaction parameter. We show that the normal electron and hole DOS functions demonstrate typical condensates double peak structures on the background of the excitonic pair formation quasiparticle spectra and we have found the evidence of the hybridization gap in the case of high-temperature limit, and small interlayer coupling parameter. Meanwhile, we show a possible crossover from the excitonic condensate regime into the band insulator state. The structure of the normal DOS spectra, in the Frenkel channel and for the strong interlayer coupling regime is found gapless for all temperature limits, which clearly indicates the strong coherence effects in the DL structure, and the excitonic condensates therein. We have shown that the excitonic pair formation and pair condensation occurs simultaneously in the DL system, in contrast with the purely three-dimensional (3D) or two-dimensional cases (2D), discussed previously.