Dynamic Jahn-Teller Mechanism of Superconductivity in MgB$_2$

TL;DR

This paper introduces a new superconductivity mechanism in MgB$_2$ driven by dynamic Jahn-Teller effects and electron-phonon interactions, explaining high critical temperature and specific heat anomalies.

Contribution

It presents a novel theory linking dynamic Jahn-Teller effects with two-gap superconductivity in MgB$_2$, which accounts for key experimental observations.

Findings

High $T_c$ explained by dynamic Jahn-Teller mechanism

Two isotropic superconducting gaps identified

Anomalous specific heat behavior accounted for

Abstract

We propose a novel mechanism of superconductivity in MgB$_2$ based on the dynamic electronic structure of the $p\sigma$-orbitals coupled with $e_{2g}$ phonons. A nonconventional superconducting state is found to arise frome lectron-phonon interactions in the presence of additional pairing channels made available by the dynamic Jahn-Teller effects. A partially broken pseudo-spin symmetry in this Jahn-Teller system, together with two-phonon exchange pairing, naturally gives rise to two distinct gaps both of which are basically isotropic in the ($k_x$, $k_y$) space. Important experimental observations including high $T_c$ and the anomalous specific heat are explained using this theory.