21 research outputs found
Spin-3/2 physics of semiconductor hole nanowires: Valence-band mixing and tunable interplay between bulk-material and orbital bound-state spin splittings
We present a detailed theoretical study of the electronic spectrum and Zeeman
splitting in hole quantum wires. The spin-3/2 character of the topmost
bulk-valence-band states results in a strong variation of subband-edge g
factors between different subbands. We elucidate the interplay between quantum
confinement and heavy-hole - light-hole mixing and identify a certain
robustness displayed by low-lying hole-wire subband edges with respect to
changes in the shape or strength of the wire potential. The ability to address
individual subband edges in, e.g., transport or optical experiments enables the
study of holes states with nonstandard spin polarization, which do not exist in
spin-1/2 systems. Changing the aspect ratio of hole wires with rectangular
cross-section turns out to strongly affect the g factor of subband edges,
providing an opportunity for versatile in-situ tuning of hole-spin properties
with possible application in spintronics. The relative importance of cubic
crystal symmetry is discussed, as well as the spin splitting away from
zone-center subband edges.Comment: 16 pages, 12 figures, RevTe
Lande-like formula for the g factors of hole-nanowire subband edges
We have analyzed theoretically the Zeeman splitting of hole-quantum-wire
subband edges. As is typical for any bound state, their g factor depends on
both an intrinsic g factor of the material and an additional contribution
arising from a finite bound-state orbital angular momentum. We discuss the
quantum-confinement-induced interplay between bulk-material and orbital
effects, which is nontrivial due to the presence of strong spin-orbit coupling.
A compact analytical formula is provided that elucidates this interplay and can
be useful for predicting Zeeman splitting in generic hole-wire geometries.Comment: 4 pages, 2 figure
Fano effect in a ring-dot system with tunable coupling
Transport measurements are presented on a quantum ring that is tunnel-coupled
to a quantum dot. When the dot is in the Coulomb blockade regime, but strongly
coupled to the open ring, Fano line shapes are observed in the current through
the ring, when the electron number in the dot changes by one. The symmetry of
the Fano resonances is found to depend on the magnetic flux penetrating the
area of the ring and on the strength of the ring-dot coupling. At temperatures
above T=0.65 K the Fano effect disappears while the Aharonov-Bohm interference
in the ring persists up to T=4.2 K. Good agreement is found between these
experimental observations and a single channel scattering matrix model
including decoherence in the dot.Comment: 9 pages, 6 figure
Higher harmonics of azimuthal anisotropy in relativistic heavy ion collisions in HYDJET++ model
The LHC data on azimuthal anisotropy harmonics from PbPb collisions at
center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in
the framework of the HYDJET++ model. The cross-talk of elliptic and
triangular flow in the model generates both even and odd harmonics of
higher order. Comparison with the experimental data shows that this mechanism
is able to reproduce the and centrality dependencies of
quadrangular flow , and also the basic trends for pentagonal and
hexagonal flows.Comment: 12 pages including 13 figures as EPS-files; prepared using LaTeX
package for publication in the European Physical Journal
Spin-filtering and charge- and spin-switching effects in a quantum wire with periodically attached stubs
Spin-dependent electron transport in a periodically stubbed quantum wire in
the presence of Rashba spin-orbit interaction (SOI) is studied via the
nonequilibrium Green's function method combined with the Landauer-Buttiker
formalism. The coexistence of spin filtering, charge and spin switching are
found in the considered system. The mechanism of these transport properties is
revealed by analyzing the total charge density and spin-polarized density
distributions in the stubbed quantum wire. Furthermore, periodic spin-density
islands with high polarization are also found inside the stubs, owing to the
interaction between the charge density islands and the Rashba SOI-induced
effective magnetic field. The proposed nanostructure may be utilized to devise
an all-electrical multifunctional spintronic device.Comment: 4 pages, 4 figure