Rashba effect

The Rashba effect (named after Emmanuil Iossifowitsch Raschba ) is a specific coupling of the electron spin to the orbital movement of the electron. It is an essential effect of the spin-orbit interaction , whose contribution is proportional to the electron energy is known to cross product of the electric field at the location of the electron and its pulse , scalar multiplied with the spinning , . It is crucial that there is an inversion asymmetry of the structure of the system, more precisely: that the potential that the electron gas encloses in two dimensions ( 2DEG ) is asymmetrical. This has so far been used in spin field effect transistors (spin FETs) at low temperatures in certain high-purity semiconductor heterostructures such as e.g. B. _Realized in _0.53 Ga _0.47 As / In _0.52 Al _0.48 As: the (extrinsic!) Influence of the spin takes place here by a voltage that can be controlled by a gate electrode. The electric field is perpendicular to the direction of movement of the electron, i.e. H. perpendicular to the observed surface or interface, and - in classic terms - causes a precession movement that changes the spin orientation. The spin-orbit coupling is correctly described by means of the Dirac equation by a special development term. ${\displaystyle E}$ ${\displaystyle p}$ ${\displaystyle \sigma }$ ${\displaystyle \Delta E\approx [E\times p]\cdot \sigma }$

The Rashba term is often compared with the so-called Dresselhaus effect, also a symmetry effect, but which is completely intrinsic and differs from the Rashba effect in essential details (e.g. in the asymmetry mentioned).

meaning

At present (late 2010) the Rashba effect is u. a. discussed in connection with the occurrence of certain topological excitations at crystal surfaces and interfaces, e.g. B. in connection with so-called. Skyrmion excitations. In addition, the effect is of outstanding importance in spintronics . The concept of spin transistors , which many semiconductor researchers are currently working on, is based on this effect . The starting material is i. d. Usually so-called semiconductor heterostructures. Spin transistors are expected to further miniaturize the components and shorten the switching times.

literature

• EI Rashba: Svoistva poluprovodnikov s petlei ekstremumov. I. Tsiklotronnyi i Kombirovannyi rezonans v magnitnom pole, perpendikulyarnom ploskosti petli . In: Fizika tverd. Tela . tape 2 , no. 6 . Leningrad 1960, p. 1224-1238 .
  • English publication: EI Rashba: Properties of semiconductors with an extremum loop. 1. Cyclotron and combinational resonance in a magnetic field perpendicular to the plane of the loop . In: Sov. Phys. Solid state . tape 2 , 1960, p. 1109-1122 .
• YA Bychkov, EI Rashba: Oscillatory effects and the magnetic susceptibility of carriers in inversion layers . In: Journal of Physics C-Solid State Physics . tape 17 , no. 33 , 1984, pp. 6039-6045 , doi : 10.1088 / 0022-3719 / 17/33/015 .
• Junsaku Nitta, Tatsushi Akazaki, Hideaki Takayanagi, Takatomo Enoki: Gate Control of Spin-Orbit Interaction in an Inverted In0.53Ga0.47As / In0.52Al0.48As heterostructure . In: Physical Review Letters . tape 78 , 1997, pp. 1335-1338 , doi : 10.1103 / PhysRevLett.78.1335 .

Web links

• weltderphysik.de; Spintronics with Magnetic Effects (2003)

References and footnotes

1. ↑ See e.g. B. a colloquium announcement at the University of Regensburg: uni-regensburg.de ( Memento from October 14, 2013 in the Internet Archive ) (PDF) and Christian Pfleiderer , Magnetismus mit Drehsinn , Physik Journal 11/2010, p. 25