37 research outputs found
Fluctuated spin-orbital texture of Rashba-split surface states in real and reciprocal space
Spin-orbit interaction (SOI) in low-dimensional systems, namely Rashba
systems and the edge states of topological materials, is extensively studied in
this decade as a promising source to realize various fascinating spintronic
phenomena, such as the source of the spin current and spin-mediated energy
conversion. Here, we show the odd fluctuation in the spin-orbital texture in a
surface Rashba system on Bi/InAs(110)-(21) by spin- and angle-resolved
photoelectron spectroscopy and a numerical simulation based on a
density-functional theory (DFT) calculation. The surface state shows a paired
parabolic dispersion with the spin degeneracy lifted by the Rashba effect.
Although its spin polarization should be fixed in a particular direction based
on the Rashba model, the observed spin polarization varies greatly and even
reverses its sign depending on the wavenumber. DFT calculations also reveal
that the spin directions of two inequivalent Bi chains on the surface change
from nearly parallel (canted-parallel) to anti-parallel in real space in the
corresponding wavevector region. These results point out an oversimplification
of the nature of spin in Rashba and Dirac systems and provide more freedom than
expected for spin manipulation of photoelectrons.Comment: 23 pages, 7 figure
Photoemission Angular Distribution Beyond the Single Wavevector Description of Photoelectron Final States
We develop a novel simulation procedure for angle-resolved photoemission
spectroscopy (ARPES), where a photoelectron wave function is set to be an
outgoing plane wave in a vacuum associated with the emitted photoelectron wave
packet. ARPES measurements on the transition metal dichalcogenide
- are performed, and our simulations exhibit good
agreement with experiments. Analysis of our calculated final state wave
functions quantitatively visualizes that they include various waves due to the
boundary condition and the uneven crystal potential. These results show that a
more detailed investigation of the photoelectron final states is necessary to
fully explain the photon-energy- and light-polarization-dependent ARPES
spectra.Comment: 6+14 pages, 4+15 figure
Spin-polarized saddle points in the topological surface states of the elemental Bismuth revealed by a pump-probe spin-resolved ARPES
We use a pump-probe, spin-, and angle-resolved photoemission spectroscopy
(ARPES) with a 10.7 eV laser accessible up to the Brillouin zone edge, and
reveal for the first time the entire band structure, including the unoccupied
side, for the elemental bismuth (Bi) with the spin-polarized surface states.
Our data identify Bi as in a strong topological insulator phase (=1)
against the prediction of most band calculations. We unveil that the unoccupied
topological surface states possess spin-polarized saddle points yielding the
van Hove singularity, providing an excellent platform for the future
development of opto-spintronics.Comment: 6 pages, 4 figure