Negative-Temperature State Formed and Interactions Inverted by Symmetric Monocycle Optical Pulse Excitation

TL;DR

This paper demonstrates theoretically that symmetric monocycle optical pulses can induce a negative-temperature state and invert interactions in correlated electron systems, using exact diagonalization in one-dimensional models.

Contribution

It reveals that symmetric monocycle pulses can create negative-temperature states and invert interactions, a phenomenon previously unreported in such symmetric excitation scenarios.

Findings

Negative-temperature states are induced by symmetric monocycle pulses.

Electron-electron and electron-phonon interactions are inverted at maximum energy absorption.

The phenomena are demonstrated in one-dimensional dimerized extended Peierls-Hubbard and Holstein models.

Abstract

The excited state dynamics of correlated electron and electron-phonon systems triggered by an oscillating electric-field pulse of large amplitude are theoretically investigated. A "negative-temperature" state and inversion of electron-electron and electron-phonon interactions are induced even by a symmetric monocycle pulse. This fact is numerically demonstrated, using the exact diagonalization method, in a band-insulator phase of one-dimensional three-quarter-filled strongly dimerized extended Peierls-Hubbard and Holstein models. When the total-energy increment is maximized as a function of the electric field amplitude, the occupancy of the bonding and antibonding orbitals is inverted to produce a negative-temperature state. Around this state, the dependences of time-averaged electron-electron and electron-phonon correlation functions on interaction parameters are opposite to those in the ground state.