Vibronic Excitation Dynamics in Orbitally Degenerate Correlated Electron System

TL;DR

This paper develops a theoretical framework to analyze vibronic excitation dynamics in orbitally degenerate correlated electron systems, accounting for local vibronic states and inter-site interactions across various Jahn-Teller coupling strengths.

Contribution

It introduces a generalized spin-wave approximation that incorporates local vibronic states, enabling analysis of excitation modes in orbital-lattice coupled systems from weak to strong coupling regimes.

Findings

Identification of a low-energy dispersive vibronic mode.

Discovery of a high-energy multi-peak mode as Flanck-Condon excitations.

The formalism applies to various orbital-lattice coupled materials.

Abstract

Orbital-lattice coupled excitation dynamics in orbitally degenerate correlated systems are examined. We present a theoretical framework, where both local vibronic excitations and superexchange-type inter-site interactions are dealt with on an equal footing. We generalize the spin-wave approximation so as to take local vibronic states into account. Present method is valid from weak to strong Jahn-Teller coupling magnitudes. Two characteristic excitation modes coexist; a low-energy dispersive mode and high-energy multi-peak mode. These are identified as a collective vibronic mode, and Flanck-Condon excitations in a single Jahn-Teller center modified by the inter-site interactions, respectively. Present formalism covers vibronic dynamics in several orbital-lattice coupled systems.