Dramatic effective mass reduction driven by strong electronic correlations

TL;DR

This study uses angle-resolved photoemission to show that strong electronic correlations in 1T-TiSe2 cause a significant reduction in effective mass at low temperatures, challenging the usual notion that interactions increase quasiparticle mass.

Contribution

It provides experimental evidence of effective mass reduction driven by electronic correlations, explained by the exciton condensate phase model.

Findings

Dramatic conduction band renormalization below 100K

Substantial effective mass reduction of charge carriers

Correlation with low-temperature resistivity downturn

Abstract

We present angle-resolved photoemission experiments on 1T-TiSe2 at temperatures ranging from 13K to 288K. The data evidence a dramatic renormalization of the conduction band below 100K, whose origin can be explained with the exciton condensate phase model. The renormalization translates into a substantial effective mass reduction of the dominant charge carriers and can be directly related to the low temperature downturn of the resistivity of 1T-TiSe2. This observation is in opposition to the common belief that strong interactions produce heavier quasiparticles through an increased effective mass.