2005 APS March Meeting
Monday–Friday, March 21–25, 2005;
Los Angeles, CA
Session H4: Recent Developments in Semiconductor Heterostructure Spin Physics
8:00 AM–11:00 AM,
Tuesday, March 22, 2005
LACC
Room: 515A
Sponsoring
Unit:
DCMP
Chair: David Awschalom, University of California-Santa Barbara
Abstract ID: BAPS.2005.MAR.H4.5
Abstract: H4.00005 : Spin susceptibility of AlAs two-dimensional electron systems
10:24 AM–11:00 AM
Preview Abstract
Abstract
Author:
Mansour Shayegan
(Princeton University)
Bulk AlAs has multiple conduction band minima at the X points of the
Brillouin zone, giving rise to ellipsoidal conduction electron Fermi
surfaces, similar to those of Si, but with only three full ellipsoids
occupied. The AlAs electrons have a larger and anisotropic effective mass
($m_{l}$ = 1.1, $m_{t}$ = 0.21) in comparison to the GaAs electrons ($m$* =
0.067). The effective Lande g-factor of electrons in bulk AlAs ($g$* = 2) is
also much larger in magnitude and of a different sign than in GaAs ($g$* = -
0.44). These properties combine to make the AlAs electron system very
different from the more commonly studied GaAs system. By confining electrons
in modulation-doped AlAs quantum wells we can obtain two-dimensional
electron systems (2DESs) with very high low-temperature mobilities.
Moreover, by choosing the proper well width, and applying uniaxial stress,
we can populate the valleys with their major axis lying either in the 2D
plane or out-of-plane. In this talk, we will present results of our
measurement of several properties of AlAs 2DESs, with an emphasis on their
spin susceptibility. In particular, when the electrons occupy the
out-of-plane valley in a very narrow ($<$ 5nm wide) AlAs quantum well, we
find that the measured spin susceptibility increases as the density is
lowered, quantitatively following the prediction of the quantum Monte Carlo
calculations. The measured susceptibility in wider AlAs wells where the
electrons occupy the in-plane valleys, however, is puzzling: at a given
density, the susceptibility is \textit{larger} when the electrons occupy one valley rather
than two valleys. This observation counters the common assumption that a
two-valley 2DES is effectively more dilute than a single-valley system
because of its smaller Fermi energy.
Work performed in collaboration with E.P. DePoortere, O. Gunawan, Y.P.
Shkolikov, E. Tutuc, and K. Vakili, and supported by the NSF.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.H4.5