Spin Hall effect

The spin Hall effect is a quantum mechanical effect, which can be seen in some ways analogous to the classical Hall effect. The main differences to the classical Hall effect here include:

• Instead of a charge current, a spin current flows transverse to the sample, ie For example, in the y- direction, while the direction of movement of the electrons is, the longitudinal direction (x -direction). It is proportional to the electric field that drives the movement of electrons. This refers to the spin Hall conductivity.
• There is no external magnetic field is required. The effect is due to spin-dependent scattering of electrons at defects in the sample ( extrinsic spin Hall effect). In spin-orbit coupled systems of the spin Hall effect also occurs in ideal systems which have no defects (intrinsic spin Hall effect).

Experiments

Theoretically, the spin Hall effect was predicted back in the 1960s, but the first time experimentally in 2004 by YK Kato, David Awschalom, inter alia, demonstrated. Has the effect, for example, in GaAs - semiconductor structures is compared at temperatures of 30 K with the ordinary Hall - effect, has been known for over a hundred years, but the spin Hall effect is smaller by orders of magnitude. In 2006 he has also been detected at room temperature (ie, at about 300 K), in ZnSe structures.

Method

The location-dependent measurement of the spin distribution can be done by Kerr -rotation microscopy. This exploits that certain materials incident by their magnetization, the plane of polarization to rotate plane-polarized light. As a collection of a spin orientation corresponding to an effective magnetization, a map of the spin polarization can be created by scanning the sample. The first evidence of Kato, Awschalom et al. was carried out by the Kerr rotation.

Technical application

Hopes of a controlled generation of spin currents can be significant technical advances in storage media ( MRAM) and spin transistor as well as important steps towards the development of a quantum computer, the realization possibility, however, is controversial.