A tale of two kinds of exceptional point in a hydrogen molecule

TL;DR

This paper investigates two distinct types of exceptional points in a non-Hermitian, parity-time symmetric hydrogen molecule, revealing new physics in a simple two-site Hubbard model with non-Hermiticity from kinetic and orbital energies.

Contribution

It identifies and characterizes two different kinds of exceptional points in a non-Hermitian hydrogen molecule, highlighting their dependence on interaction strength and expanding understanding of PT-symmetric quantum systems.

Findings

Discovery of two different types of exceptional points in the model.

Dependence of EPs on interaction strength varies between the two types.

Potential for new physics emerging from a simple two-site Hubbard Hamiltonian.

Abstract

We study the parity and time-reversal ($\mathcal{PT}$) symmetric quantum physics in a non-Hermitian non-relativistic hydrogen molecule with local (Hubbard type) Coulomb interaction. We consider non-Hermiticity generated from both kinetic and orbital energies of the atoms and encounter the existence of two different types of exceptional points (EPs) in pairs. These two kinds of EP are characteristically different and depend differently on the interaction strength. Our discovery may open the gates of a rich physics emerging out of a simple Hamiltonian resembling a two-site Hubbard model.