APS March Meeting 2012
Volume 57, Number 1
Monday–Friday, February 27–March 2 2012;
Boston, Massachusetts
Session H19: Invited Session: Current-Driven Spin Textures
8:00 AM–11:00 AM,
Tuesday, February 28, 2012
Room: 253AB
Sponsoring
Units:
DCMP GMAG
Chair: Joseph Orenstein, University of California, Berkeley and Lawrence Livermore National Laboratory
Abstract ID: BAPS.2012.MAR.H19.1
Abstract: H19.00001 : Doppler velocimetry of a current driven spin helix
8:00 AM–8:36 AM
Preview Abstract
Abstract
Author:
Luyi Yang
(UC Berkeley and Lawrence Berkeley National Lab)
We present direct observation of the translational motion of spin helices in
GaAs quantum wells under the influence of applied electric fields.
Previously, the lifetime of such helices was observed by time-resolving the
amplitude of light diffracted from the periodic spin polarization [1]. This
technique cannot be applied to tracking the motion of current-driven spin
helices because diffraction amplitude is insensitive to translation of the
center of mass of a periodic structure. In this talk, we describe a new
experimental technique, Doppler spin velocimetry, capable of resolving
displacements of spin polarization at the level of 1 nm on a picosecond time
scale [2]. This is accomplished through the use of heterodyne detection to
measure the optical phase of the diffracted light. We discuss experiments in
which this technique is used to measure the motion of spin helices as a
function of temperature, in-plane electric field, and photoinduced spin
polarization amplitude. Several striking observations will be reported --
for example, the spin helix velocity changes sign as a function of
wavevector and is zero at the wavevector that yields the largest spin
lifetime. Another important observation is that the velocity of spin
polarization packets becomes equal to the drift velocity of the
high-mobility electron gas in the limit of small spin helix amplitude.
Finally, we show that spin helices continue propagate at the same speed as
the Fermi sea even when the electron drift velocity exceeds the Fermi
velocity of 10$^{7}$ cm-s$^{-1}$. In collaboration with J. D. Koralek and J.
Orenstein, UC Berkeley and LBNL, D. R. Tibbetts, J. L. Reno, and M. P.
Lilly, SNL. Supported by DOE under Contract No. DE-AC02-05CH11231 and
DE-AC04-94AL85000.
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[1] J. D. Koralek et al., ``Emergency of the persistent spin helix in semiconductor quantum wells,'' Nature 458, 610-613 (2009).
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[2] L. Yang et al, ``Doppler velocimetry of spin propagation in a
two-dimensional electron gas,'' to appear in Nature Physics.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.H19.1