Gap formation in the density of states as the indicator of metal-insulator transition caused by electron-phonon coupling

Abstract

This research explores the electron-phonon coupling effect on manganite system transport properties. Using the Holstein Phonon model, which has been documented to capture metal-insulator transitions in single band model, we investigate the electron-phonon coupling effect. We also look into insulator phase forming criteria, using more realistic phonon model for manganite system; the Jahn-Teller model.To observe the forming of gap energy in Jahn-Teller model, we also do the separate computation for Q2 and Q3 modes. For this computation, interactions between electron spins and Mn ions spin are omitted. Computation is done using Dynamical Mean Field Theory (DMFT). The computation results are shown through the Density of State (DoS) Profile for various modes, electron filling, electron-phonon coupling, and temperature. Our computation results prove that Jahn-Teller model with a certain minimum electron-phonon coupling constant (g) can produce energy gap, where chemical potential (µ) fall precisely in the middle of energy gap that causes the system to be an insulator. This result applies to any electron filling value (x). Computation with electron-phonon coupling variation and temperature shows that the width of the energy gap increases along with the increase of both variables.