14,486 research outputs found
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 controls of spin and valley in these
2D materials. The spin-valley coupling at the valence band edges suppresses
spin and valley relaxation, as flip of each index alone is forbidden by the
valley contrasting spin splitting. Valley Hall and spin Hall effects coexist in
both electron-doped and hole-doped systems. Optical interband transitions have
frequency-dependent polarization selection rules which allow selective
photoexcitation of carriers with various combination of valley and spin
indices. Photo-induced spin Hall and valley Hall effects can generate long
lived spin and valley accumulations on sample boundaries. The physics discussed
here provides a route towards the integration of valleytronics and spintronics
in multi-valley materials with strong spin-orbit coupling and inversion
symmetry breaking.Comment: published versio
Experimental implementation of fully controlled dephasing dynamics and synthetic spectral densities
Engineering, controlling, and simulating quantum dynamics is a strenuous
task. However, these techniques are crucial to develop quantum technologies,
preserve quantum properties, and engineer decoherence. Earlier results have
demonstrated reservoir engineering, construction of a quantum simulator for
Markovian open systems, and controlled transition from Markovian to
non-Markovian regime. Dephasing is an ubiquitous mechanism to degrade the
performance of quantum computers. However, a fully controllable all-purpose
quantum simulator for generic dephasing is still missing. Here we demonstrate
full experimental control of dephasing allowing us to implement arbitrary
decoherence dynamics of a qubit. As examples, we use a photon to simulate the
dynamics of a qubit coupled to an Ising chain in a transverse field and also
demonstrate a simulation of non-positive dynamical map. Our platform opens the
possibility to simulate dephasing of any physical system and study fundamental
questions on open quantum systems.Comment: V2: Added some text and new figur
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