Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time

• URL: http://arxiv.org/abs/2106.03359v3
• Date: Tue, 20 Jun 2023 10:05:03 GMT
• Title: Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time
• Authors: Garima Gupta, Kenji Watanabe, Takashi Taniguchi, and Kausik Majumdar
• Abstract summary: In monolayer transition metal dichalcogenide semiconductors, valley coherence degrades rapidly due to a combination of fast scattering and inter-valley exchange interaction. Here we demonstrate fully valley coherent excitons by observing 100% degree of linear polarization in steady state photoluminescence. This is the first report in which the excitons are found to be valley coherent in the entire lifetime in monolayer semiconductors.
• Score: 1.189955933770711
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: In monolayer transition metal dichalcogenide semiconductors, valley coherence degrades rapidly due to a combination of fast scattering and inter-valley exchange interaction. This leads to a sub-picosecond valley coherence time, making coherent manipulation of exciton a highly challenging task. Using monolayer MoS2 sandwiched between top and bottom graphene, here we demonstrate fully valley coherent excitons by observing ~100% degree of linear polarization in steady state photoluminescence. This is achieved in this unique design through a combined effect of (a) suppression in exchange interaction due to enhanced dielectric screening, (b) reduction in exciton lifetime due to a fast inter-layer transfer to graphene, and (c) operating in the motional narrowing regime. We disentangle the role of the key parameters affecting valley coherence by using a combination of calculation (solutions of Bethe-Salpeter and Maialle-Silva-Sham equations) and a careful choice of design of experiments using four different stacks with systematic variation of screening and exciton lifetime. To the best of our knowledge, this is the first report in which the excitons are found to be valley coherent in the entire lifetime in monolayer semiconductors, allowing optical readout of valley coherence possible.

Related papers

• Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers [0.929965561686354]
  We show that strong doping levels beyond $1013$cm$-2$ can induce 61% and 37% valley contrast at room temperature in TMD monolayers. Our results indicate that charged excitons in TMD monolayers can be utilized as quantum units in designing of practical valleytronic devices operating at 300 K.
  arXiv  Detail & Related papers  (2023-08-21T07:01:39Z)
• Optically controlled single-valley exciton doublet states with tunable internal spin structures and spin magnetization generation [0.0]
  We introduce a novel kind of optically controllable doubly degenerate exciton states that come from a single valley. Our findings open new routes to control quantum degrees of freedom, paving the way for applications in spintronics and quantum information science.
  arXiv  Detail & Related papers  (2022-11-07T06:43:47Z)
• On the Su-Schrieffer-Heeger model of electron transport: low-temperature optical conductivity by the Mellin transform [62.997667081978825]
  We describe the low-temperature optical conductivity as a function of frequency for a quantum-mechanical system of electrons that hop along a polymer chain. Our goal is to show vias how the interband conductivity of this system behaves as the smallest energy bandgap tends to close.
  arXiv  Detail & Related papers  (2022-09-26T23:17:39Z)
• All-optical valley switch and clock of electronic dephasing [0.0]
  We introduce a coherent control protocol to turn on, off and switch the valley polarization at faster timescales than electronic and valley decoherence. We show that we can extract the electronic dephasing time $T$ from the valley Hall conductivity.
  arXiv  Detail & Related papers  (2022-04-01T12:45:22Z)
• Entanglement and correlations in fast collective neutrino flavor oscillations [68.8204255655161]
  Collective neutrino oscillations play a crucial role in transporting lepton flavor in astrophysical settings. We study the full out-of-equilibrium flavor dynamics in simple multi-angle geometries displaying fast oscillations. We present evidence that these fast collective modes are generated by the same dynamical phase transition.
  arXiv  Detail & Related papers  (2022-03-05T17:00:06Z)
• Enhanced superconductivity and various edge modes in modulated $t$-$J$ chains [6.0413288393037305]
  We numerically investigate the ground state of the extended $t$-$J$ Hamiltonian with periodic local modulations in one dimension. We obtain a rich ground-state phase diagram consisting of the metallic state, the superconducting state, the phase separation, and insulating states at commensurate fillings.
  arXiv  Detail & Related papers  (2021-11-26T19:00:18Z)
• Chemical tuning of spin clock transitions in molecular monomers based on nuclear spin-free Ni(II) [52.259804540075514]
  We report the existence of a sizeable quantum tunnelling splitting between the two lowest electronic spin levels of mononuclear Ni complexes. The level anti-crossing, or magnetic clock transition, associated with this gap has been directly monitored by heat capacity experiments. The comparison of these results with those obtained for a Co derivative, for which tunnelling is forbidden by symmetry, shows that the clock transition leads to an effective suppression of intermolecular spin-spin interactions.
  arXiv  Detail & Related papers  (2021-03-04T13:31:40Z)
• Light-matter interactions near photonic Weyl points [68.8204255655161]
  Weyl photons appear when two three-dimensional photonic bands with linear dispersion are degenerated at a single momentum point, labeled as Weyl point. We analyze the dynamics of a single quantum emitter coupled to a Weyl photonic bath as a function of its detuning with respect to the Weyl point.
  arXiv  Detail & Related papers  (2020-12-23T18:51:13Z)
• Deterministic single-atom source of quasi-superradiant $N$-photon pulses [62.997667081978825]
  Scheme operates with laser and cavity fields detuned from the atomic transition by much more than the excited-state hyperfine splitting. This enables reduction of the dynamics to that of a simple, cavity-damped Tavis-Cummings model with the collective spin determined by the total angular momentum of the ground hyperfine level.
  arXiv  Detail & Related papers  (2020-12-01T03:55:27Z)
• Microscopic theory of cavity-confined monolayer semiconductors: polariton-induced valley relaxation and the prospect of enhancing and controlling the valley pseudospin by chiral strong coupling [0.0]
  We apply a microscopic theory of exciton-polaritons in cavity-confined monolayer transition-metal dichalcogenides. We show how chiral cavity photons interact with the valley degrees of freedom of the active material.
  arXiv  Detail & Related papers  (2020-08-06T18:00:05Z)
• Optically pumped spin polarization as a probe of many-body thermalization [50.591267188664666]
  We study the spin diffusion dynamics of 13C in diamond, which we dynamically polarize at room temperature via optical spin pumping of engineered color centers. We find good thermal contact throughout the nuclear spin bath, virtually independent of the hyperfine coupling strength. Our results open intriguing opportunities to study the onset of thermalization in a system by controlling the internal interactions within the bath.
  arXiv  Detail & Related papers  (2020-05-01T23:16:33Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.