Mapping out the emergence of topological features in the highly alloyed topological Kondo insulators Sm$_{1-x}M_x$B$_6$ ($M$=Eu, Ce)

TL;DR

This study investigates how topological features in highly alloyed SmB6 topological Kondo insulators evolve with magnetic doping and temperature, revealing persistent topological states even at high impurity levels.

Contribution

It provides the first detailed mapping of topological electronic structure evolution in highly alloyed SmB6, highlighting the robustness of topological states against extreme doping.

Findings

Topological surface states persist up to 30% Eu and 50% Ce doping.

Topological coherence remains despite the loss of the insulating gap.

Revised band symmetry understanding explains the persistence of topological features.

Abstract

SmB6 is a strongly correlated material that has been attributed as a topological insulator and a Kondo insulator. Recent studies have found the topological surface states and low temperature insulating character to be profoundly robust against magnetic and non-magnetic impurities. Here, we use angle resolved photoemission spectroscopy to chart the evolution of topologically-linked electronic structure features versus magnetic doping and temperature in Sm$_{1-x}$M$_x$B$_6$ (M=Eu, Ce). Topological coherence phenomena are observed out to unprecedented ~30% Eu and 50% Ce concentrations that represent extreme nominal hole and electron doping, respectively. Theoretical analysis reveals that a recent re-designation of the topologically inverted band symmetries provides a natural route to reconciling the persistence of topological surface state emergence even as the insulating gap is lost through decoherence.