The impact of metallic contacts on spin-polarized photocurrents in topological insulator $\text{Bi}_2\text{Se}_3$ nanowires

TL;DR

This study investigates how metallic contacts influence spin-polarized photocurrents in topological insulator Bi2Se3 nanowires, revealing enhanced currents at contact interfaces and complex spatial distributions driven by thermoelectric and spin Nernst effects.

Contribution

It provides new insights into the role of metallic contacts in modulating spin-polarized photocurrents in topological insulator nanowires, highlighting the interplay of thermoelectric and spin Nernst effects.

Findings

Enhanced photocurrent values at contact interfaces.

Dipole-like distribution of spin-polarized current near contacts.

Thermoelectric effects contribute to current enhancement.

Abstract

Recently, a new quantum phase, the topological insulator, has been vividly investigated in a variety of materials. Its unique bandstructure allows for optical generation and control of spin-polarized currents based on the circular photogalvanic effect. In this paper, we generate and distinguish the different photocurrent contributions via the the polarization of the driving light wave. We discuss the helicity-dependent spin-polarized current and the polarization independent thermoelectric current as spatially resolved maps, focusing on the influence of the topological insulator/metallic contact interface. We observe for both current contributions a significant enhancement of the current values at the topological insulator/metallic contact interface and moreover a dipole-like distribution of the spin-polarized current close to the contacts. We discuss the general behavior of the thermovoltage as a three-material Seebeck effect and explain the enhanced values by the acceleration of the photoelectrons generated in the space charge region of the topological insulator/metallic contact interface. Furthermore, we interpret the temperature gradient together with the spin Nernst effect as a possible origin for the enhancement and dipole-like distribution of the spin-polarized current.