18 research outputs found
Determining the spin-orbit coupling via spin-polarized spectroscopy of magnetic impurities
We study the spin-resolved spectral properties of the impurity states
associated to the presence of magnetic impurities in two-dimensional, as well
as one-dimensional systems with Rashba spin-orbit coupling. We focus on Shiba
bound states in superconducting materials, as well as on impurity states in
metallic systems. Using a combination of a numerical T-matrix approximation and
a direct analytical calculation of the bound state wave function, we compute
the local density of states (LDOS) together with its Fourier transform (FT). We
find that the FT of the spin-polarized LDOS, a quantity accessible via
spin-polarized STM, allows to accurately extract the strength of the spin-orbit
coupling. Also we confirm that the presence of magnetic impurities is strictly
necessary for such measurement, and that non-spin-polarized experiments cannot
have access to the value of the spin-orbit coupling.Comment: 26 pages, 6 figure
RKKY interaction on the surface of three-dimensional Dirac semimetals
We study the RKKY interaction between two magnetic impurities located on the
surface of a three-dimensional Dirac semimetal with two Dirac nodes in the band
structure. By taking into account both bulk and surface contributions to the
exchange interaction between the localized spins, we demonstrate that the
surface contribution in general dominates the bulk one at distances larger than
the inverse node separation due to a weaker power-law decay. We find a strong
anisotropy of the surface term with respect to the spins being aligned along
the node separation axis or perpendicular to it. In the many impurity dilute
regime, this implies formation of quasi-one-dimensional magnetic stripes
orthogonal to the node axis. We also discuss the effects of a surface
spin-mixing term coupling electrons from spin-degenerate Fermi arcs.Comment: 7,5 pages, 3 figures (+4 pages of Appendixes
Topology from triviality
We show that bringing into proximity two topologically trivial systems can give rise to a topological phase. More specifically, we study a 1D metallic nanowire proximitized by a 2D superconducting substrate with a mixed s-wave and p-wave pairing, and we demonstrate both analytically and numerically that the phase diagram of such a setup can be richer than reported before. Thus apart from the two “expected” well-known phases (i.e., where the substrate and the wire are both simultaneously trivial or topological), we show that there exist two peculiar phases in which the nanowire can be in a topological regime while the substrate is trivial and vice versa
Photogalvanic effect in the HgTe/CdTe topological insulator due to edge-bulk optical transitions
We study theoretically the 2D HgTe/CdTe quantum well topological insulator illuminated by circularly polarized light with frequencies higher than the difference between the equilibrium Fermi level and the bottom of the conduction band (THz range). We show that electron-hole asymmetry results in spin-dependent electric dipole transitions between edge and bulk states, and we predict an occurrence of a circular photocurrent. If the edge state is tunnel-coupled to a conductor, then the photocurrent can be detected by measuring an electromotive force in the conductor, which is proportional to the photocurrent
Photogalvanic effects in topological insulators
<p>We discuss optical absorption in topological insulators and study possible photoelectric effects theoretically. We found that absorption of circularly polarized electromagnetic waves in two-dimensional topological insulators results in electric current in the conducting 1D edge channels, the direction of the current being determined by the light polarization. We suggest two ways of inducing such a current: due to magnetic dipole electron transitions stimulated by irradiation of frequency below the bulk energy gap, and due to electric dipole transitions in the bulk at frequencies larger than the energy gap with subsequent capture of the photogenerated carriers on conducting edge states.</p>