Optical probe of electrostatic doping in an n-type Mott insulator

TL;DR

This study demonstrates electrostatic electron doping in an n-type Mott insulator using a heterojunction, revealing spectral changes indicative of a transition towards metallicity through optical spectroscopy.

Contribution

It introduces a novel heterojunction approach for electrostatic doping in n-type Mott insulators and observes associated electronic state modifications.

Findings

Electrostatic doping up to 6% per Cu atom achieved.

Spectral weight transfer observed in Mott-gap state.

Evidence of metallic state formation through optical spectroscopy.

Abstract

Electrostatic doping into an $n$-type Mott insulator Sm$_{2}$CuO$_{4}$ has been successfully achieved with use of the heterojunction with an $n$-type band semiconductor Nb-doped SrTiO$_{3}$. The junction exhibits rectifying current-voltage characteristics due to the interface band discontinuity and the formation of depleted region. The application of reverse bias electric field on this junction enables the field-effect electron doping (presumably up to 6% per Cu atom) to the Mott insulator. The electro-modulation absorption spectroscopy could clearly show a large modification of the Mott-gap state accompanying the spectral weight transfer to the lower-energy region, reminiscent of formation of a metallic state.