Center for Semiconductor Physics in Nanostructures
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Importance: The asymmetry of a two-dimensional electron system’s
(2DES’s) confinement potential is predicted to increase the spin-splitting
of its energy band structure due to a spin-orbit coupling phenomenon called
the Rashba effect. If this modification is sufficiently large at zero
applied magnetic field, it could enable the development of a new type
of transistor based on electron spin precession. Nearly all the experimental
evidence for zero-field spin splitting in 2DESs has been based on observed
beating in Shubnikov-de Haas oscillations. Several of these experiments,
however, reveal inconsistencies with theoretical expectations. A complementary
experimental technique could contribute to resolving these issues.
We have demonstrated a far-infrared photoconductivity measurement that
directly probes the Rashba spin-splitting as a function of applied magnetic
field, B. Our experiments were performed on InSb-based 2DESs, which are
expected to exhibit strong spin-orbit coupling effects. Our data demonstrate
that electron spin resonance is a valuable technique for studying the
Rashba effect and confirm that this effect is large in asymmetric InSb-based
2DESs.
---G.A. Khodaparast, R.E. Doezema, S.J. Chung, K.J. Goldammer
and M.B. Santos, C-SPIN
(Japan J. Appl. Phys., in press)
Figure 1: Spin splitting as deduced from electron spin resonance in remotely-doped InSb quantum wells, is shown as a function of applied magnetic field. The solid symbols are for asymmetric structures, while the open symbols are for symmetric structures. The solid lines are calculations of Zeeman splitting and do not include the Rashba effect. The relevant Landau level indices, n, for several transitions are indicated. Note that the data for the symmetric structures agree with the calculations, but not the asymmetric structures do not. The deviations from theory indicate the strength of the Rashba effect in asymmetric InSb quantum wells.
Figure 2: Direct measurement of spin splitting due to the Rashba Effect.
