20 research outputs found
All-electrical detection of the relative strength of Rashba and Dresselhaus spin-orbit interaction in quantum wires
We propose a method to determine the relative strength of Rashba and
Dresselhaus spin-orbit interaction from transport measurements without the need
of fitting parameters. To this end, we make use of the conductance anisotropy
in narrow quantum wires with respect to the directions of an in-plane magnetic
field, the quantum wire and the crystal orientation. We support our proposal by
numerical calculations of the conductance of quantum wires based on the
Landauer formalism which show the applicability of the method to a wide range
of parameters.Comment: 4 pages, 4 figure
Direct determination of spin orbit interaction coefficients and realization of the persistent spin helix symmetry
The spin orbit interaction plays a crucial role in diverse fields of
condensed matter, including the investigation of Majorana fermions, topological
insulators, quantum information and spintronics. In III V zinc blende
semiconductor heterostructures, two types of spin orbit interaction, Rashba and
Dresselhaus act on the electron spin as effective magnetic fields with
different directions. They are characterized by coefficients alpha and beta,
respectively. When alpha is equal to beta, the so called persistent spin helix
symmetry is realized. In this condition, invariance with respect to spin
rotations is achieved even in the presence of the spin orbit interaction,
implying strongly enhanced spin lifetimes for spatially periodic spin modes.
Existing methods to evaluate alpha/beta require fitting analyses that often
include ambiguity in the parameters used. Here, we experimentally demonstrate a
simple and fitting parameter free technique to determine alpha/beta and to
deduce the absolute values of alpha and beta. The method is based on the
detection of the effective magnetic field direction and the strength induced by
the two spin orbit interactions. Moreover, we observe the persistent spin helix
symmetry by gate tuning.Comment: 34 pages with 7 figures including supplementary information. appears
in Nature Nanotechnology (2014) Published online 13 July 201
Spin relaxation: From 2D to 1D
In inversion asymmetric semiconductors, spin-orbit interactions give rise to
very effective relaxation mechanisms of the electron spin. Recent work, based
on the dimensionally constrained D'yakonov Perel' mechanism, describes
increasing electron-spin relaxation times for two-dimensional conducting layers
with decreasing channel width. The slow-down of the spin relaxation can be
understood as a precursor of the one-dimensional limit
Spin dynamics in semiconductors
This article reviews the current status of spin dynamics in semiconductors
which has achieved a lot of progress in the past years due to the fast growing
field of semiconductor spintronics. The primary focus is the theoretical and
experimental developments of spin relaxation and dephasing in both spin
precession in time domain and spin diffusion and transport in spacial domain. A
fully microscopic many-body investigation on spin dynamics based on the kinetic
spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published
in Physics Reports
1-MHz operation of 1.7-cycle multiple plate compression at 35-W average output power
We generated 1.7-cycle and 35-J pulses at a 1-MHz repetition rate by
using two-stage multiple plate continuum compression of Yb-laser pulses with
80-W average input power. By adjusting the plate positions with careful
consideration of the thermal lensing effect due to the high average power, we
compressed the output pulse with a 184-fs initial duration to 5.7 fs by using
only group-delay-dispersion compensation. This pulse achieved a sufficient beam
quality ( < 1.5) reaching a focused intensity over 10 W/cm and
a high spatial-spectral homogeneity (98%). Our study holds promise for a
MHz-isolated-attosecond-pulse source for advanced attosecond spectroscopic and
imaging technologies with unprecedentedly high signal-to-noise ratios.Comment: 4 pages, 6 figure
Gate-controlled persistent spin helix state in (In,Ga)As quantum wells
In layered semiconductors with spin-orbit interaction (SOI) a persistent spin helix (PSH) state with suppressed spin relaxation is expected if the strengths of the Rashba and Dresselhaus SOI terms, α and ÎČ, are equal. Here we demonstrate gate control and detection of the PSH in two-dimensional electron systems with strong SOI including terms cubic in momentum. We consider strain-free InGaAs/InAlAs quantum wells and first determine a ratio α/ÎČâ1 for nongated structures by measuring the spin-galvanic and circular photogalvanic effects. Upon gate tuning the Rashba SOI strength in a complementary magnetotransport experiment, we monitor the complete crossover from weak antilocalization via weak localization to weak antilocalization, where the emergence of weak localization reflects a PSH-type state. A corresponding numerical analysis reveals that such a PSH-type state indeed prevails even in presence of strong cubic SOI, however no longer at α=ÎČ