Jahn-Teller Coupled Charge Density Wave in A Two Orbital Double Exchange System

TL;DR

This paper investigates how Jahn-Teller phonons induce charge density waves in a two orbital double exchange system, revealing mode-dependent effects on stability, thermodynamics, and collective excitations.

Contribution

It formulates a model for Jahn-Teller coupled charge density waves in a two orbital double exchange system, highlighting the role of specific distortion modes and their impact on system properties.

Findings

Q2 mode yields lowest free energy.

Heat capacity exhibits T^3 behavior at low temperature.

Electron-lattice interaction significantly affects collective modes.

Abstract

In a two orbital double exchange model we formulate Jahn-Teller coupled charge density wave in one electron per lattice site limit. Softening of Jahn-Teller phonons corresponding to distortion modes $Q_2$ or $Q_3$ associated with perfect nesting of Fermi surface leads to this instability at low temperature. The gap equation for charge density wave state and its dependences on electron-lattice coupling are calculated explicitly when any one of the Jahn-Teller modes is excited cooperatively. We find that the $Q_2$ distortion mode yields lowest free energy. The calculated heat capacity for each mode shows $T^3$ behavior at low temperature. Effect of electron-lattice interaction on collective mode, such as amplitude mode, is more pronounced when the excited mode is $Q_2$.