Quasiparticles at the verge of localization near the Mott metal-insulator transition in a two-dimensional material

TL;DR

This study investigates the behavior of quasiparticles near the Mott transition in a two-dimensional organic material, revealing significant spectral weight redistribution and effective mass increase, with theoretical modeling aligning well with experimental results.

Contribution

It provides a combined experimental and theoretical analysis of quasiparticle dynamics near the Mott transition in a 2D material, highlighting spectral weight transfer and mass enhancement.

Findings

Spectral weight redistributes as the Mott transition is approached.

Quasiparticle effective mass increases near the insulating phase.

The Hubbard model with dynamical mean-field theory accurately describes the data.

Abstract

The dynamics of charge carriers close to the Mott transition is explored theoretically and experimentally in the quasi two-dimensional organic charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br$_x$Cl$_{1-x}$, with varying Br content. The frequency dependence of the conductivity deviates significantly from simple Drude model behavior: there is a strong redistribution of spectral weight as the Mott transition is approached and with temperature. The effective mass of the quasiparticles increases considerably when coming close to the insulating phase. A dynamical mean-field-theory treatment of the relevant Hubbard model gives a good quantitative description of the experimental data.