05.12.10 - First time realization of a multi-valued spin-switch in the solid state. Read Nature Materials publication on

We realize for the first time a multi-valued spin-switch in the solid state.
Polaritons are light-matter quasiparticles. As most quantum particles, they have a spin which can be spin-up (+1) or spin-down (-1).

We use polaritons under quantum confinement to play with a single, narrow-linewidth, confined level, which s macroscopically occupied by a few hundreds of polaritons.

To control the spin state of the polariton, we use continuous wave laser excitation with variable polarization.
In a first time, we realize the state-of-the-art of spin switching: within very low power variations (few tens of nW effective power), the spin state reversibly flips from 0 to +1 or from 0 to -1.
+1 corresponds to all spins up, -1 to all spins down and 0 to a balanced, coherent mixture of spin-up and spin-down polaritons.

Then we demonstrate that, under a precise regime, it is possible to have the three spin states coexisting (+1, 0 and -1) for a single excitation condition, and to flip reversibly and selectively between them. That is, we realize a new device, the spin Schmitt trigger, which is an analog of the Schmitt trigger in electronics.

These results opens new pathways to optical spintronics and computing and might also lead to the development of multi-valued logic devices. "

Author:Roland CernaSource:Laboratory of Quantum Optoelectronics