Spins go their own way

A semiconductor device that integrates electron spin injection, transport, modulation and detection in a single structure provides an important step in versatility for both fundamental research and practical spintronic applications

Photo-Induced Spin Dynamics in Semiconductor Quantum Wells

We experimentally investigate the dynamics of spins in GaAs quantum wells under applied electric bias by photoluminescence (PL) measurements excited with circularly polarized light. The bias-dependent circular polarization of PL (PPL) with and without magnetic field is studied. ThePPLwithout magnetic field is found to be decayed with an enhancement of increasing the strength of the negative bias. However,PPLin a transverse magnetic field shows oscillations under an electric bias, indicating that the precession of electron spin occurs in quantum wells. The results are discussed based on the electron–hole exchange interaction in the electric field

Semiconductor spintronics - Spins go their own way

A semiconductor device that integrates electron spin injection, transport, modulation and detection in a single structure provides an important step in versatility for both fundamental research and practical spintronic applications

Electrical creation of spin polarization in silicon at room temperature

The control and manipulation of the electron spin in semiconductors is central to spintronics1,2, which aims to represent digital information using spin orientation rather than electron charge. Such spin-based technologies may have a profound impact on nanoelectronics, data storage, and logic and computer architectures.\ud Recently it has become possible to induce and detect spin\ud polarization in otherwise non-magnetic semiconductors (gallium arsenide and silicon) using all-electrical structures3–9, but so far only at temperatures below 150K and in n-type materials, which limits further development. Here we demonstrate room-temperature electrical\ud injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation.\ud A spin splitting as large as 2.9meV is created in n-type\ud silicon, corresponding to an electron spin polarization of 4.6%. The extracted spin lifetime is greater than 140 ps for conduction electrons in heavily doped n-type silicon at 300K and greater than 270 ps for holes in heavily doped p-type silicon at the same temperature.\ud The spin diffusion length is greater than 230nmfor electrons\ud and 310nm for holes in the corresponding materials. These results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature, and to the exploration of their prospects and the fundamental rules that govern their behaviour.\u

Determination of the spin-lifetime anisotropy in graphene using oblique spin precession

We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields