# Excitonic giant-dipole potentials in cuprous oxide

## TL;DR

This paper predicts a new type of giant-dipole excitons in cuprous oxide under crossed electric and magnetic fields, revealing potential for large electric dipole moments and novel excitonic states.

## Contribution

It introduces a theoretical model for giant-dipole excitons in Cu2O, including a pseudoseparation of motion and exact gauge-invariant Hamiltonian formulation.

## Key findings

- Potential well depths up to 380 μeV
- Excitonic dipole moments around three million Debye
- Outer well separations up to several micrometers

## Abstract

In this work we predict the existence of a novel species of Wannier excitons when exposed to crossed electric and magnetic fields. In particular, we present a theory of giant-dipole excitons in $\textrm{Cu}_2\rm O$ in crossed fields. Within our theoretical approach we perform a pseudoseparation of the center-of-mass motion for the field-dressed excitonic species, thereby obtaining an effective single-particle Hamiltonian for the relative motion. For arbitrary gauge fields we exactly separate the gauge-dependent kinetic energy terms from the effective single-particle interaction potential. Depending on the applied field strengths and the specific field orientation, the potential for the relative motion of electron and hole exhibits an outer well at spatial separations up to several micrometers and depths up to $380\, \mu \rm eV$, leading to possible permanent excitonic electric dipole moments of around three million Debye.