Far-infrared absorption and the metal-to-insulator transition in hole-doped cuprates

TL;DR

This study investigates the metal-to-insulator transition in hole-doped cuprates through far-infrared optical conductivity, revealing a gap formation consistent with ARPES data and a Mott-like transition mechanism.

Contribution

It provides new insights into the gap formation and optical signatures associated with the MIT in cuprates, linking infrared absorption features to electronic structure changes.

Findings

A small gap opens at low temperatures in the far-infrared spectrum.

The gap formation correlates with the transformation of the Drude peak into infrared absorption.

A mid-infrared band softens with doping but is less affected by the MIT.

Abstract

By studying the optical conductivity of BSLCO and YCBCO, we show that the metal-to-insulator transition (MIT) in these hole-doped cuprates is driven by the opening of a small gap at low T in the far infrared. Its width is consistent with the observations of Angle-Resolved Photoemission Spectroscopy in other cuprates, along the nodal line of the k-space. The gap forms as the Drude term turns into a far-infrared absorption, whose peak frequency can be approximately predicted on the basis of a Mott-like transition. Another band in the mid infrared softens with doping but is less sensitive to the MIT.