TY - JOUR

T1 - Gigantic 2D laser-induced photovoltaic effect in magnetically-doped topological insulators for surface zero-bias spin-polarized current generation

AU - Shikin, A. M.

AU - Voroshin, V.

AU - Rybkin, A. G.

AU - Kokh, K. A.

AU - Tereshchenko, O. E.

AU - Ishida, Y.

AU - Kimura, A.

N1 - Funding Information: The work was supported by the grant of the Saint Petersburg State University for scientific investigations (grant No. 15.61.202.2015) and the grant of the Russian Science Foundation (grant No. 17-12-01047), in the part of the crystal growth and structural characterization.

PY - 2018/1

Y1 - 2018/1

N2 - A new kind of 2D photovoltaic effect (PVE) with the generation of anomalously large surface photovoltage up to 210 meV in magnetically doped topological insulators (TIs) has been studied by the laser time-resolved pump-probe angle-resolved photoelectron spectroscopy. The PVE has maximal efficiency for TIs with high occupation of the upper Dirac cone (DC) states and the Dirac point located inside the fundamental energy gap. For TIs with low occupation of the upper DC states and the Dirac point located inside the valence band the generated surface photovoltage is significantly reduced. We have shown that the observed giant PVE is related to the laser-generated electron-hole asymmetry followed by accumulation of the photoexcited electrons at the surface. It is accompanied by the 2D relaxation process with the generation of zero-bias spin-polarized currents flowing along the topological surface states (TSSs) outside the laser beam spot. As a result, the spin-polarized current generates an effective in-plane magnetic field that is experimentally confirmed by the k II-shift of the DC relative to the bottom non-spin-polarized conduction band states. The realized 2D PVE can be considered as a source for the generation of zero-bias surface spin-polarized currents and the laser-induced local surface magnetization developed in such kind 2D TSS materials.

AB - A new kind of 2D photovoltaic effect (PVE) with the generation of anomalously large surface photovoltage up to 210 meV in magnetically doped topological insulators (TIs) has been studied by the laser time-resolved pump-probe angle-resolved photoelectron spectroscopy. The PVE has maximal efficiency for TIs with high occupation of the upper Dirac cone (DC) states and the Dirac point located inside the fundamental energy gap. For TIs with low occupation of the upper DC states and the Dirac point located inside the valence band the generated surface photovoltage is significantly reduced. We have shown that the observed giant PVE is related to the laser-generated electron-hole asymmetry followed by accumulation of the photoexcited electrons at the surface. It is accompanied by the 2D relaxation process with the generation of zero-bias spin-polarized currents flowing along the topological surface states (TSSs) outside the laser beam spot. As a result, the spin-polarized current generates an effective in-plane magnetic field that is experimentally confirmed by the k II-shift of the DC relative to the bottom non-spin-polarized conduction band states. The realized 2D PVE can be considered as a source for the generation of zero-bias surface spin-polarized currents and the laser-induced local surface magnetization developed in such kind 2D TSS materials.

KW - 2D systems

KW - electronic and spin structure

KW - magnetically doped topological insulators

KW - spin-polarized currents

KW - surface photovoltaic effect

KW - time-resolved photoemission spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85040099677&partnerID=8YFLogxK

U2 - 10.1088/2053-1583/aa928a

DO - 10.1088/2053-1583/aa928a

M3 - Article

VL - 5

JO - 2D Materials

JF - 2D Materials

SN - 2053-1583

IS - 1

M1 - 015015

ER -