Spin injection, spin transport and spin coherence

Abstract

We discuss advances, advantages and problems of spintronics through the example of a semiconductor laser whose emission intensity and polarization are modulated by the spin orientation of electrons. We show that spin transport should be feasible at room temperature and present possible concepts and first results concerning spin injection at high temperatures. Finally, we describe the coherent dynamics of coupled electron and hole spins in a quantum mechanical picture and measure the magnetic field-induced dynamics of localized excitons in a 3 nm GaAs quantum well. The system is capable of performing a quantum controlled not operation (CNOT), which realizes a basic two-qubit operation of quantum information processing in a semiconductor nanostructure.

Design considerations for semiconductor spin lasers

“…Changing the growth direction of the GaAs quantum wells from (001) to (110), the spin relaxation times reach the nanosecond regime since the Dyakonov-Perel mechanism is suppressed in these systems for spin orientations in the growth direction [14,8], and the expected threshold reduction approaches the maximum of 50%. A similar reduction is in principle expected for wide band-gap semiconductors like ZnSe where the spin-orbit interaction is weak [15].…”

Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes

“…Investigation at higher J region is extremely interesting not only in view of elucidating the mechanism of nonlinear effects, but also to clarify whether stimulated emission with CP is possible in the lateral-waveguidetype geometry in which stimulated light emission with linear polarization dominates. Exploitation toward both shorter and longer wavelengths with different materials combinations, together with electrical CP switching (20,54,55) and high-frequency modulation (56,57), is another important direction in view of investigating the usefulness of spin-LEDs in the existing and new applications, e.g., the chiral resolution in synthetic chemistry (58), diagnosis of cancerous tissues (59), circularly polarized ellipsometry (60), the optically enhanced nuclei imaging (61), LP-polarization-insensitive 3D display (62), quantum eraser technique (63), optical secure communications (64), and beyond.…”

“…Among those, the highest circular polarization (CP) value, P CP ≡ {I(σ + ) and I(σ − ) the intensity of right-and left-handed EL component, respectively, was P CP ∼ 0.3 ∼ 0.35 at RT in the external magnetic flux of B = 0.8 T, which was achieved in the context of studying the spinfiltering effect of the MgO TB (18,19). Most of the past works regarding spin-LED were carried out under the vertical arrangement with low J ranging from 0.1 to 1 A/cm 2 and forcing spins aligned vertically by applying out-of-plane external magnetic fields (20). With vertical-cavity surface-emitting laser structure incorporating the quantum wells (QWs) (21)(22)(23) or thick active layer (24) together with a means of a vertical optical resonator, pure-CP lasing was demonstrated by the optical pumping up to RT (21)(22)(23)(24).…”

Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons

“…[1][2][3] This allows us to investigate spin relaxation mechanisms in semiconductors using techniques such as time-resolved Faraday rotation and time-resolved photoluminescence. [4][5][6][7] In this work, we study the optical generation of spin correlations in bulk semiconductors using polarization squeezed light. This can be seen as either an extension of optical orientation to manipulate the fluctuations of the spin ͗S͑t͒ · S͑tЈ͒͘ or as a way to transfer correlations from the light to the electrons.…”