New many-particle system consisting of electron pairs and holes in a two-dimensional crystal

TL;DR

This paper explores a novel many-particle system in a 2D crystal where electron pairs and holes coexist, showing how exchange-correlation effects can stabilize these pairs and analyzing their charge-density excitations.

Contribution

It demonstrates the stabilization of electron pairs in a 2D crystal due to many-particle effects and characterizes their excitation spectrum, revealing a new quantum system.

Findings

Electron pairs can be stabilized in a 2D crystal with sufficient potential.

A metastable electron-pair band exists between the lowest single-electron bands.

Charge-density excitation spectrum of the system is calculated.

Abstract

When atoms are organized into a crystal, the single-electron energy levels of individual atoms form energy bands. However, there also exist electron-pair states in atoms. We found previously that the counterpart of these electron-pair states of individual atoms may survive in a two-dimensional square-lattice crystal. When the amplitude of the crystal potential is larger than a certain value, a metastable electron-pair band arises between the two lowest single-electron energy bands. In this paper, we demonstrate that the many-particle exchange-correlation corrections renormalize the energy bands and may stabilize the electron pairs for certain hole and electron-pair densities in the two-dimensional crystal. Therefore, depending upon the crystal potential and free carrier densities, there may exist a new many-particle system consisting of electron pairs and holes. Furthermore, we calculate the charge-density excitation spectrum in this new many-particle system.