Synchrotron radiation induced magnetization in magnetically-doped and pristine topological insulators

TL;DR

This study demonstrates how synchrotron radiation induces magnetization in topological insulators through asymmetric photoexcitation, spin accumulation, and spin-torque effects, confirmed by experiments and ab initio calculations.

Contribution

It reveals the mechanism of SR-induced magnetization in TIs, linking photoexcitation asymmetry to spin polarization and magnetization, supported by experimental and theoretical analysis.

Findings

Asymmetric photoexcitation varies with photon energy.

SR induces measurable in-plane and out-of-plane magnetization.

Magnetization persists above the Curie temperature.

Abstract

Quantum mechanics postulates that any measurement influences the state of the investigated system. Here, by means of angle-, spin-, and time-resolved photoemission experiments and ab initio calculations we demonstrate how non-equal depopulation of the Dirac cone (DC) states with opposite momenta in V-doped and pristine topological insulators (TIs) created by a photoexcitation by linearly polarized synchrotron radiation (SR) is followed by the hole-generated uncompensated spin accumulation and the SR-induced magnetization via the spin-torque effect. We show that the photoexcitation of the DC is asymmetric, that it varies with the photon energy, and that it practically does not change during the relaxation. We find a relation between the photoexcitation asymmetry, the generated spin accumulation and the induced spin polarization of the DC and V 3d states. Experimentally the SR-generated in-plane and out-of-plane magnetization is confirmed by the $k_{\parallel}$-shift of the DC position and by the splitting of the states at the Dirac point even above the Curie temperature. Theoretical predictions and estimations of the measurable physical quantities substantiate the experimental results.