DattaDasModell

Datta-Das Modell (Datta-Das spin transistor) is a theoretical framework introduced by Supriyo Datta and Biswajit Das in 1990 that describes a spin field-effect transistor (SFET) built from a semiconductor channel with ferromagnetic source and drain contacts. The key idea is that the current through the channel can be modulated by electrically controlling the spin precession of carriers as they travel between the contacts, using the Rashba spin-orbit interaction.

In the model, a gate electric field induces Rashba spin-orbit coupling in a quasi-one-dimensional semiconductor channel. This coupling causes the spins of conduction electrons to precess as they propagate, with a precession angle θ that is proportional to the Rashba parameter α and the channel length L (approximately θ ≈ 2 m* α L / ħ^2). The spin orientation of electrons arriving at the drain depends on this precession, and the conductance is determined by the projection of the rotated spin onto the magnetization direction of the drain contact. In the idealized case of perfect spin injection and detection with aligned polarizations, the conductance varies as G ∝ cos^2(θ/2), allowing electrical readout and control of current via gate voltage.

Significance and limitations: The Datta-Das model highlighted a route to all-electrical control of spin in a semiconductor and inspired extensive spintronics research. Real implementations face challenges such as spin relaxation, imperfect spin injection/detection, scattering, and maintaining ballistic transport, which have limited practical realization of SFETs. Nevertheless, the model remains a foundational concept in spin-based electronics and the study of Rashba-driven spin dynamics.

See also: spintronics, Rashba effect, spin field-effect transistor.