On the Coulomb-dipole transition in mesoscopic classical and quantum electron-hole bilayers

TL;DR

This paper investigates the transition between Coulomb and dipole interactions in electron-hole bilayers, analyzing classical ground states and quantum states across different layer separations, revealing significant changes in system configurations and excitations.

Contribution

It provides a detailed analysis of classical and quantum ground states in electron-hole bilayers during the Coulomb-dipole transition, highlighting differences from pure systems and exploring quantum states with Hartree-Fock calculations.

Findings

Classical ground states differ from pure Coulomb or dipole systems.

Normal mode frequencies change drastically with layer separation.

Quantum Hartree-Fock states show significant variation across parameters.

Abstract

We study the Coulomb-to-dipole transition which occurs when the separation $d$ of an electron-hole bilayer system is varied with respect to the characteristic in-layer distances. An analysis of the classical ground state configurations for harmonically confined clusters with $N\leq30$ reveals that the energetically most favorable state can differ from that of two-dimensional pure dipole or Coulomb systems. Performing a normal mode analysis for the N=19 cluster it is found that the lowest mode frequencies exhibit drastic changes when $d$ is varied. Furthermore, we present quantum-mechanical ground states for N=6, 10 and 12 spin-polarized electrons and holes. We compute the single-particle energies and orbitals in self-consistent Hartree-Fock approximation over a broad range of layer separations and coupling strengths between the limits of the ideal Fermi gas and the Wigner crystal.