The Crossover from a Bad Metal to a Frustrated Mott Insulator

TL;DR

This paper introduces a novel Monte Carlo method to study the Mott transition in an anisotropic triangular lattice, revealing a pseudogap phase with unique spectral and transport properties relevant to organic materials.

Contribution

The study presents a real space Monte Carlo approach that accurately captures magnetic fluctuations and pseudogap phenomena in frustrated Mott systems, advancing understanding of the bad metal to insulator crossover.

Findings

Detection of a wide pseudogap phase between metal and insulator

Pronounced momentum dependence of quasiparticle damping

Predictions testable via tunneling and photoemission experiments

Abstract

We use a novel Monte Carlo method to study the Mott transition in an anisotropic triangular lattice. The real space approach, retaining extended spatial correlations, allows an accurate treatment of non trivial magnetic fluctuations in this frustrated structure. Choosing the degree of anisotropy to mimic the situation in the quasi-two dimensional organics, $\kappa-$(BEDT-TTF)$_2$Cu[N(CN)$_2$]-X, we detect a wide pseudogap phase, with anomalous spectral and transport properties, between the `ungapped' metal and the `hard gap' Mott insulator. The magnetic fluctuations also lead to pronounced momentum dependence of quasiparticle damping and pseudogap formation on the Fermi surface as the Mott transition is approached. Our predictions about the `bad metal' state have a direct bearing on the organics where they can be tested via tunneling, angle resolved photoemission, and magnetic structure factor measurement.