Magnetic Doping and Kondo Effect in Bi2Se3 Nanoribbons

TL;DR

This paper reports the synthesis of magnetically doped Bi2Se3 nanoribbons and demonstrates the Kondo effect at low temperatures, highlighting potential for spintronics applications in topological insulator nanostructures.

Contribution

It introduces a vapor-liquid-solid growth method for magnetic doping of Bi2Se3 nanoribbons and confirms the presence of magnetic impurities through transport measurements.

Findings

Low-temperature transport shows a clear Kondo effect below 30 K.

Magnetic doping concentration is less than 2%.

Doping enables magnetic control of topological surface states.

Abstract

A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically-protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surface-to-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically-doped Bi2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than ~ 2%, low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics.