78th Annual Meeting of the Southeastern Section of the APS
Volume 56, Number 9
Wednesday–Saturday, October 19–22, 2011;
Roanoke, Virginia
Session BB: Nano Materials
8:30 AM–10:30 AM,
Thursday, October 20, 2011
Room: Crystal Ballroom B
Chair: Michel Pleimling, Virginia Polytechnic Institute and State University
Abstract ID: BAPS.2011.SES.BB.3
Abstract: BB.00003 : Spin-dependent quantum transport in nanoscaled geometries
9:30 AM–10:00 AM
Preview Abstract
Abstract
Author:
Jean J. Heremans
(Virginia Tech, Department of Physics)
We discuss experiments where the spin degree of freedom leads to
quantum interference phenomena in the solid-state. Under
spin-orbit interactions (SOI), spin rotation modifies
weak-localization to weak anti-localization (WAL). WAL's
sensitivity to spin- and phase coherence leads to its use in
determining the spin coherence lengths Ls in materials, of
importance moreover in spintronics. Using WAL we measure the
dependence of Ls on the wire width w in narrow nanolithographic
ballistic InSb wires, ballistic InAs wires, and diffusive Bi
wires with surface states with Rashba-like SOI. In all three
systems we find that Ls increases with decreasing w. While theory
predicts the increase for diffusive wires with linear (Rashba)
SOI, we experimentally conclude that the increase in Ls under
dimensional confinement may be more universal, with consequences
for various applications. Further, in mesoscopic ring geometries
on an InAs/AlGaSb 2D electron system (2DES) we observe both
Aharonov-Bohm oscillations due to spatial quantum interference,
and Altshuler-Aronov-Spivak oscillations due
to time-reversed paths. A transport formalism describing quantum
coherent networks including ballistic transport and SOI allows a
comparison of spin- and phase coherence lengths extracted for
such spatial- and temporal-loop quantum interference phenomena.
We further applied WAL to study the magnetic interactions between
a 2DES at the surface of InAs and local magnetic
moments on the surface from rare earth (RE) ions (Gd3+, Ho3+, and
Sm3+). The magnetic spin-flip rate carries information about
magnetic interactions. Results indicate that the heavy RE ions
increase the SOI scattering rate and the spin-flip rate, the
latter indicating magnetic interactions. Moreover Ho3+ on InAs
yields a spin-flip rate with an unusual power 1/2 temperature
dependence, possibly characteristic of a Kondo system. We
acknowledge funding from DOE (DE-FG02-08ER46532).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.SES.BB.3