Valley polarization in MoS2 monolayers by optical pumping.

@article{Zeng2012ValleyPI,
  title={Valley polarization in MoS2 monolayers by optical pumping.},
  author={H. Zeng and J. Dai and W. Yao and Di Xiao and X. Cui},
  journal={Nature nanotechnology},
  year={2012},
  volume={7 8},
  pages={
          490-3
        }
}
Most electronic devices exploit the electric charge of electrons, but it is also possible to build devices that rely on other properties of electrons. Spintronic devices, for example, make use of the spin of electrons. Valleytronics is a more recent development that relies on the fact that the conduction bands of some materials have two or more minima at equal energies but at different positions in momentum space. To make a valleytronic device it is necessary to control the number of electrons… Expand
Control of valley polarization in monolayer MoS2 by optical helicity.
TLDR
It is demonstrated that optical pumping with circularly polarized light can achieve complete dynamic valley polarization in monolayer MoS(2) (refs 11, 12), a two-dimensional non-centrosymmetric crystal with direct energy gaps at two valleys. Expand
Valley Polarization by Spin Injection in a Light-Emitting van der Waals Heterojunction
TLDR
This demonstration of spin injection and magnetoelectronic control over valley polarization provides a new opportunity for realizing combined spin and valleytronic devices based on spin-valley locking in semiconducting TMDCs. Expand
Electrical control of the valley Hall effect in bilayer MoS2 transistors.
TLDR
It is shown that the valley Hall effect in bilayer MoS2 transistors can be controlled with a gate voltage, which is consistent with symmetry-dependent Berry curvature and valley Hall conductivity in bilayers MoS 2. Expand
Valley-polarized exciton dynamics in a 2D semiconductor heterostructure
TLDR
This work created interlayer exciton spin-valley polarization by means of circularly polarized optical pumping and determined a valley lifetime of 40 nanoseconds, which enables the visualization of the expansion of a valley-polarized exciton cloud over several micrometers. Expand
Optical generation of valley polarization in atomically thin semiconductors
Electronic valleys refer to energy extrema in momentum space. In the same way as spin is utilized for spintronics, valleys can be considered as pseudo-spins for valley based electronics andExpand
Valley-polarized exciton currents in a van der Waals heterostructure
TLDR
The generation and transport over mesoscopic distances of valley-polarized excitons in a device based on a type-II TMDC heterostructure is shown and electrostatic traps are used to increase the exciton concentration by an order of magnitude, opening the route to achieving a coherent quantum state of valley, polarizedexcitons via Bose–Einstein condensation. Expand
Direct observation of valley-coupled topological current in MoS2
TLDR
It is reported that valley current can be electrically induced and detected through the valleyHall effect and inverse valley Hall effect, respectively, in monolayer molybdenum disulfide, to enable a new generation of electronic devices using the valley degree of freedom, which can be used for future novel valleytronic applications. Expand
The valley Hall effect in MoS2 transistors
TLDR
The observation of the so-called valley Hall effect in a monolayer of MoS2 opens up new possibilities for using the valley DOF as an information carrier in next-generation electronics and optoelectronics. Expand
Realization of Valley and Spin Pumps by Scattering at Nonmagnetic Disorders.
TLDR
It is discovered that the quested valley pump of electrons or holes can be realized simply by scattering at the ubiquitous nonmagnetic disorders, not relying on any specific material property. Expand
Magnetoluminescence and valley polarized state of a two-dimensional electron gas in WS2 monolayers.
TLDR
The recombination of the negatively charged exciton in the presence of a two-dimensional electron gas is found to be circularly polarized at zero magnetic field despite being excited with unpolarized light, which indicates that the existence of a valley polarized 2DEG is caused by valley and spin locking and strong electron-electron interactions. Expand
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References

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Control of valley polarization in monolayer MoS2 by optical helicity.
TLDR
It is demonstrated that optical pumping with circularly polarized light can achieve complete dynamic valley polarization in monolayer MoS(2) (refs 11, 12), a two-dimensional non-centrosymmetric crystal with direct energy gaps at two valleys. Expand
MoS_2 as an ideal material for valleytronics: valley-selective circular dichroism and valley Hall effect
A two-dimensional honeycomb lattice harbors a pair of inequivalent valleys in the k-space electronic structure, in the vicinities of the vertices of a hexagonal Brillouin zone, K±. It is particularlyExpand
Valley filter and valley valve in graphene
The potential of graphene for carbon electronics rests on the possibilities offered by its unusual band structure to create devices that have no analogue in silicon-based electronics1,2. ConductionExpand
Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides.
We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides, making possible controlsExpand
Valley-dependent optoelectronics from inversion symmetry breaking
Inversion symmetry breaking allows contrasted circular dichroism in different $k$-space regions, which takes the extreme form of optical selection rules for interband transitions at high symmetryExpand
Atomically thin MoS₂: a new direct-gap semiconductor.
TLDR
The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N=1,2,…,6 S-Mo-S monolayers have been investigated by optical spectroscopy and the effect of quantum confinement on the material's electronic structure is traced. Expand
Valley-contrasting physics in graphene: magnetic moment and topological transport.
TLDR
The pseudospin associated with the valley index of carriers has an intrinsic magnetic moment, in close analogy with the Bohr magneton for the electron spin, forming the basis for the valley-based electronics applications. Expand
Valley-selective circular dichroism of monolayer molybdenum disulphide
TLDR
It is shown, using first principles calculations, that monolayer molybdenum disulphide is an ideal material for valleytronics, for which valley polarization is achievable via valley-selective circular dichroism arising from its unique symmetry. Expand
Graphene valley filter using a line defect.
TLDR
It is shown that electron and hole quasiparticles in graphene can be filtered according to which valley they occupy without the need to introduce confinement. Expand
Valley splitting of AlAs two-dimensional electrons in a perpendicular magnetic field.
TLDR
The splitting of the conduction-band valleys in high-mobility two-dimensional electrons confined to AlAs quantum wells appears to depend primarily on the magnitude of the perpendicular component of the magnetic field, suggesting electron-electron interaction as its origin. Expand
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