Electronic correlation determining correlated plasmons in Sb-doped Bi$_2$Se$_3$

TL;DR

This study reveals the existence of correlated plasmons in Sb-doped Bi2Se3, demonstrating how electronic correlation influences plasmonic properties and carrier dynamics, with implications for topological insulator device engineering.

Contribution

It provides experimental and theoretical evidence of correlated plasmons in a topological insulator, highlighting the role of electronic correlation in their formation and behavior.

Findings

Correlated plasmons are observed in Sb-doped Bi2Se3.

Electronic correlation affects carrier density in surface and bulk states.

Correlated plasmons are key to understanding spectral weight transfer.

Abstract

Electronic correlation is believed to play an important role in exotic phenomena such as insulator-metal transition, colossal magneto resistance and high temperature superconductivity in correlated electron systems. Recently, it has been shown that electronic correlation may also be responsible for the formation of unconventional plasmons. Herewith, using a combination of angle-dependent spectroscopic ellipsometry, angle resolved photoemission spectroscopy and Hall measurements all as a function of temperature supported by first-principles calculations, the existence of low-loss high-energy correlated plasmons accompanied by spectral weight transfer, a fingerprint of electronic correlation, in topological insulator (Bi$_{0.8}$Sb$_{0.2}$)$_2$Se$_3$ is revealed. Upon cooling, the density of free charge carriers in the surface states decreases whereas those in the bulk states increase, and that the newly-discovered correlated plasmons are key to explaining this phenomenon. Our result shows the importance of electronic correlation in determining new correlated plasmons and opens a new path in engineering plasmonic-based topologically-insulating devices.