Experimental observation of the SpinHall Effect in In
Experimental observation of the Spin-Hall Effect in In. Ga. N/Ga. N superlattices Student : Hsiu-Ju, Chang Advisor:Yang Fang, Chen
Outline • Introduction 1. Basic elements in Spin-Hall effect 2. Recent theoretical analysis 3. Experimental observation • Experiment and discussion • Summary • Future work
- Introduction Basic elements in Spin-Hall effect
- Introduction Recent theoretical analysis Ⅰ The hamiltonian of a 2 DEG with Rashba spin coupling
Red arrows : spin direction Green arrows : moment a E=0 Rate at momentum space E = EX
spin current in the y direction A where p. F+ and p. F- are the Fermi momenta of the majority and minority spin Rashba bands. When n 2 D > (mmλ^2)/(π(2πh)^4) A = 2 mλ(2πh)
spin Hall (SH) conductivity Independent of both the Rashba coupling strength and of the 2 DES density.
Recent theoretical analysis Ⅰ summary • We describe a new effect in semiconductor spintronics that leads to dissipationless spin currents in paramagnetic spinorbit coupled systems. • We argue that in a high-mobility two-dimensional electron system with substantial Rashba spin-orbit coupling, a spin current that flows perpendicular to the charge current is intrinsic. • In the usual case where both spin-orbit split bands are occupied, the intrinsic spin-Hall conductivity has a universal value for zero quasiparticle spectral broadening.
Recent theoretical analysis Ⅱ G. Y. Guo, PRL V 94 226601 (2005)
G. Y. Guo, PRL V 94 226601 (2005)
G. Y. Guo, PRL V 94 226601 (2005)
G. Y. Guo, PRL V 94 226601 (2005)
Hole concentration = 0. 1 e/cell G. Y. Guo, PRL V 94 226601 (2005)
Recent theoretical analysis Ⅱ summary • The calculated orbital-angular momentum (orbital) Hall conductivity is one order of magnitude smaller, indicating no cancellation between the spin and orbital Hall effects in bulk semiconductors. • Furthermore, it is found that the spin Hall effect can be strongly manipulated by strains.
- Introduction Experimental observation Reference: J. Wunderlich, B. Kaestner, J. Sinova, and T. Jungwirth PRL, V 94, 047204 (2005) p n
Experimental observation summary • When an electric field is applied across the hole channel, a nonzero out-of-plane component of the angular momentum is detected whose sign depends on the sign of the electric field and is opposite for the two edges. • Microscopic quantum transport calculations show only a weak effect of disorder, suggesting that the clean limit spin-Hall conductance description (intrinsic spin-Hall effect) might apply to our system.
Motivation • The SHE has been observed by Wunderlich et al. and Kato et al. for Ga. As semiconductor. • Can the SHE be observed in other semiconductors, such as nitride materials ? • The theoretical calculation reveals that the SHE can be tuned by strains, but there is no experimental evidence to prove it. • The difference of the SHE on external current has not been varified. • What will be the influence of temperature on the SHE ? • . . . .
- Slides: 20