Two routes to metallic behavior for a Kondo insulator

TL;DR

This study investigates how the magnetic gap in the Kondo insulator CeNiSn is affected by temperature, chemical doping, and magnetic field, revealing two distinct routes to metallic behavior.

Contribution

It provides experimental evidence of how doping and magnetic fields destroy the magnetic gap in CeNiSn, highlighting two different pathways to metallicity in Kondo insulators.

Findings

Doping collapses the spin gap and induces magnetic Bragg peaks.

Magnetic field and temperature smooth the spin gap without changing static susceptibility.

Two different mechanisms lead to metallic behavior in the material.

Abstract

Cold neutron spectroscopy was performed on CeNi_{1-x}Cu_xSn to investigate how the magnetic gap in the 'Kondo insulator' CeNiSn is destroyed by temperature (T), chemical substitution (x), and external magnetic field. Upon doping, the spin gap collapses and magnetic Bragg peaks occur initially (x = 0.13) at the commensurate wave vectors Q = (0,m/2,l) (m,l integer) where the higher-energy (4.1 meV) gap is located for x = 0. A magnetic field smooths the sharp spin gap structure in both momentum and energy, while leaving the associated static susceptibility unchanged, as does raising T.