Role of Se vacancies on Shubnikov de Haas oscillations in Bi2Se3: a combined magneto-resistance and positron annihilation study

TL;DR

This study investigates how selenium vacancies affect quantum oscillations in Bi2Se3 topological insulators, revealing that fewer vacancies lead to clearer 2D electronic behavior as shown by magneto-resistance and positron annihilation measurements.

Contribution

It combines magneto-resistance and positron lifetime measurements to link Se vacancies with the presence of Shubnikov de Haas oscillations in Bi2Se3.

Findings

Fewer Se vacancies correlate with stronger SdH oscillations.

Quantum oscillations indicate 2D electronic structure in low-vacancy samples.

Positron annihilation spectroscopy effectively characterizes vacancy concentrations.

Abstract

Magneto resistance measurements coupled with positron lifetime measurements, to characterize the vacancy type defects, have been carried out on the topological insulator (TI) system Bi2Se3, of varying Se/Bi ratio. Pronounced Shubnikov de Haas (SdH) oscillations are seen in nominal Bi2Se3.1 crystals for measurements performed in magnetic fields up to 15 T in the 4 K to 10 K temperature range, with field applied perpendicular to the (001) plane of the crystal. The quantum oscillations, characteristic of 2D electronic structure, are seen only in the crystals that have a lower concentration of Se vacancies, as inferred from positron annihilation spectroscopy.