Room-temperature electron spin polarization exceeding 90% in an opto-spintronic semiconductor nanostructure via remote spin filtering

Abstract

An exclusive advantage of semiconductor spintronics is its potential for optospintronics that will allow integration of spin-based information processing/storage with photon-based information transfer/communications. Unfortunately, progresses have so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at room temperature. Here, we demonstrate successful generation of conduction electron spin polarization exceeding 90% at room temperature without a magnetic field in a non-magnetic all-semiconductor nanostructure, which remains high even up to 110°C. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunneling-coupled GaNAs spin filter. We further show that the quantum-dot electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin-photon interfaces. This work demonstrates the feasibility to implement opto-spintronic functionality in common semiconductor nanostructures.

Chiral emission from resonant metasurfaces

“…Compared with previous reports (7,8,14,16), our resonant metasurface exhibits better performances in terms of DOP, directionality, and Q factor (table S1) that are retained over a wide range, from photoluminescence to lasing (table S2). This approach may improve the design of current sources of chiral light and boost their applications in photonic and quantum systems.…”

“…Progress in this field relies on continued breakthroughs in the demonstration of chiral materials and chiral optical cavities ( 6 ). Chiral materials have been intensively explored, and emission of light with 0.95 degree of polarization (DOP) has recently been demonstrated at room temperature by applying electrical or optical spin injection ( 7 , 8 ). Research on chiral optical micro- and nanocavities is slightly behind ( 6 ).…”

Designing Semiconductor Nanowires for Efficient Photon Upconversion via Heterostructure Engineering

“…Under the above bandgap excitation through one-photon absorption, that is, a linear process, the PL spectra (the solid lines) are dominated by a near-band-edge emission caused by recombination of excitons trapped within the band tail states. The PL spectra experience a red shift upon N incorporation, which is caused by a N-induced decrease in the bandgap energy due to the well-known giant bandgap bowing in dilute nitrides. − Simultaneously, spectral broadening of the PL emission upon N incorporation is observed, which is typical for dilute nitrides and is determined by an energy distribution of the localized states. ,, The same emissions, though significantly weaker, can also be excited when the excitation photon energy ( hυ exc ) is tuned below the bandgap ( E g ). The corresponding spectra of such upconverted PL (UPL) emission are shown in Figure b by the dotted lines, where the excitation energies are marked by the dotted arrows.…”

“…In this work, we attempt to push the limit of low-power upconversion efficiency in semiconductor nanostructures, through the approach of radial heterostructure engineering of NWs by exploring radial core/shell NWs with a nitrogen free III–V core and a dilute-nitride shell of a lower bandgap with a favorable band alignment between the core and shell. Dilute nitrides, obtained from parental III–V materials by substitution of a few percent of group-V atoms with nitrogen (N), have a number of attractive properties promising for optoelectronic, photovoltaic, and spintronic applications. ,− A large difference in size and electronegativity between the N atom and the replaced group-V host atom dramatically affects the electronic structure of the forming alloy: It leads to a giant decrease in the bandgap energy, which can be as much as 270 meV/%N, caused by a dramatic down-shift of the conduction band (CB) edge upon N incorporation, while the valence band (VB) edge remains practically unaffected . Using dilute-nitride alloys in such nanostructured NWs is expected to facilitate easy and wide-range tuning of the band alignment at the heterointerface thanks to this N-induced giant down-shift of the CB states, which broadens and extends the usable range of the primary light wavelength.…”

Efficient Room‐Temperature Voltage Control of Picosecond Optical Spin Orientation Using a III‐V Semiconductor Nanostructure

“…The next step is the integration of spintronics into semiconductor engineering, in which spin polarization (corresponding to spin information) can be generated, manipulated, conserved, and transferred to circularly polarized light. [4,8,9] Semiconductor quantum dots (QDs) are the most promising candidates for the spin-photon interface because of their suppressed carrier spin relaxation [10,11] in addition to high efficiency of optical transitions. [12] The manipulation of spin orientation in QDs in electron and hole occurs, emitting PL with negative polarization.…”