Quantum dot spin valve

Schematic representation of
a quantum dot spin valve

Spin dynamics on the quantum dot

A quantum dot spin valve (Engl. Quantum Dot spin valve ) is so far only theoretically described but not yet experimentally realized, mesoscopic , spintronisches component . Possible applications are in the field of quantum computers or in the magnetic storage of information .

It consists of a Einzelniveau- quantum dot , the above tunnel barrier of ferromagnetic electrode is coupled whose magnetizations in any direction and can show. ${\displaystyle \mathbf {n} _{L}}$ ${\displaystyle \mathbf {n} _{R}}$

If a transport voltage is applied to the system , electrons can tunnel to the quantum dot from the left, for example. Since there are more electrons with spin in the direction than with spin in the left electrode , the tunneled electron will preferably have a spin in the former direction. In order to be able to leave the quantum dot in the right electrode, a spin in the direction is preferably necessary. Therefore, due to the conservation of angular momentum on the quantum dot, a spin in the direction will be established in the stationary case . Due to the Pauli ban, this now leads to the transport through the quantum dot spin valve being blocked. ${\displaystyle V}$ ${\displaystyle \mathbf {n} _{L}}$ ${\displaystyle -\mathbf {n} _{L}}$ ${\displaystyle \mathbf {n} _{R}}$ ${\displaystyle \mathbf {n} _{L}-\mathbf {n} _{R}}$

In addition, due to the Coulomb interaction of the electrons on the quantum dot, there is a magnetic exchange field that causes the spin to precession on the quantum dot. This leads to the fact that the amount of the spin ( expected value) is smaller and is rotated out of its unfavorable direction blocking the transport, which ultimately reduces the spin valve effect.

swell

1. ^ Matthias Braun, Jürgen König, Jan Martinek: Theory of transport through quantum-dot spin valves in the weak-coupling regime. In: Physical Review B. 70, 2004, doi : 10.1103 / PhysRevB.70.195345 . arxiv : cond-mat / 0404455