Fingerprints of hot-phonon physics in time-resolved correlated quantum lattice dynamics

TL;DR

This paper introduces a novel method to detect hot-phonon effects in materials by analyzing lattice correlations, demonstrated on MgB₂, and applicable to other high-symmetry materials.

Contribution

It proposes a new approach to identify hot phonons via lattice inter-atomic correlations, expanding the toolkit for studying electron-phonon interactions.

Findings

Identified signatures of hot phonons in MgB₂ through lattice correlation analysis.

Demonstrated the generality of the method for high-symmetry materials.

Provided insights into the symmetry properties of hot-phonon modes.

Abstract

The time dynamics of the energy flow from electronic to lattice degrees of freedom in pump-probe setups could be strongly affected by the presence of a hot-phonon bottleneck, which can sustain longer coherence of the optically excited electronic states. Recently, hot-phonon physics has been experimentally observed and theoretically described in MgB$_2$, the electron-phonon based superconductor with $T_{\rm c}\approx 39$ K. By employing a combined ab-initio and quantum-field-theory approach and by taking MgB$_2$ as an example, here we propose a novel path for revealing the presence and characterizing the properties of hot phonons through a direct analysis of the information encoded in the lattice inter-atomic correlations. Such method exploits the underlying symmetry of the $E_{2g}$ hot modes characterized by a out-of-phase in-plane motion of the two boron atoms. Since hot phonons occur typically at high-symmetry points of the Brillouin zone, with specific symmetries of the lattice displacements, the present analysis is quite general and it could aid in revealing the hot-phonon physics in other promising materials, such as graphene, boron nitride, or black phosphorus.