Title: Synchrotron radiation induced magnetization in magnetically-doped and pristine topological insulators,
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.