A5053462701- Graphene research and applications
- 2D Materials and Applications
- Quantum and electron transport phenomena
- Perovskite Materials and Applications
- Molecular Junctions and Nanostructures
- Chalcogenide Semiconductor Thin Films
- Topological Materials and Phenomena
- Semiconductor Quantum Structures and Devices
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Advanced biosensing and bioanalysis techniques
- Magnetic properties of thin films
- Plasmonic and Surface Plasmon Research
- Electrochemical sensors and biosensors
- Nanocluster Synthesis and Applications
- Photonic Crystals and Applications
- Iron oxide chemistry and applications
- Ga2O3 and related materials
- Quantum Dots Synthesis And Properties
- Electrochemical Analysis and Applications
- Advanced Memory and Neural Computing
- Conducting polymers and applications
- Magnetic Properties and Synthesis of Ferrites
- Lung Cancer Diagnosis and Treatment
- Urban and Freight Transport Logistics
Electric Power University
2020-2025
University of Rochester
2016-2025
Hanoi University of Science and Technology
2020-2023
Lac Hong University
2018
Institut Català de Nanociència i Nanotecnologia
2012-2016
Consejo Superior de Investigaciones Científicas
2016
Universitat Autònoma de Barcelona
2011-2015
Vietnam National University Ho Chi Minh City
2012-2013
Graphene has attracted significant interest both for exploring fundamental science and a wide range of technological applications. Chemical vapor deposition (CVD) is currently the only working approach to grow graphene at wafer scale, which required industrial Unfortunately, CVD intrinsically polycrystalline, with pristine grains stitched together by disordered grain boundaries, can be either blessing or curse. On one hand, boundaries are expected degrade electrical mechanical properties...
Abstract The coupling between spin, charge, and lattice degrees of freedom plays an important role in a wide range fundamental phenomena. Monolayer semiconducting transitional metal dichalcogenides have emerged as outstanding platform for studying these effects. Here, we report the observation multiple valley phonons – with momentum vectors pointing to corners hexagonal Brillouin zone resulting exciton complexes monolayer semiconductor WSe 2 . We find that lead efficient intervalley...
Coulomb interactions in atomically thin materials are remarkably sensitive to variations the dielectric screening of environment, which can be used control exotic quantum many-body phases and engineer exciton potential landscapes. For decades, static or frequency-independent approximations response, where increased is predicted cause an energy redshift resonance, have been sufficient. These were first applied wells more recently extended with initial success layered transition metal...
Polycrystalline graphene is a patchwork of coalescing grains varying lattice orientations and size, resulting from the chemical vapor deposition (CVD) growth at random nucleation sites on metallic substrates. The morphology grain boundaries has become an important topic given its fundamental role in limiting mobility charge carriers polycrystalline graphene, as compared to mechanically exfoliated samples. Here we report new insights current understanding transport geometries. We created...
Recently, the celebrated Keldysh potential has been widely used to describe Coulomb interaction of few-body complexes in monolayer transition-metal dichalcogenides. Using this model charged excitons (trions), one finds a strong dependence binding energy on whether is suspended air, supported SiO$_2$, or encapsulated hexagonal boron-nitride. However, empirical values trion energies show weak configuration. This deficiency indicates that description still lacking important class materials. We...
The role of defect-induced zero-energy modes on charge transport in graphene is investigated using Kubo and Landauer calculations. By tuning the density random distributions monovacancies either equally populating two sublattices or exclusively located a single sublattice, all conduction regimes are covered from direct tunneling through evanescent to mesoscopic bulk disordered graphene. Depending measurement geometry, defect density, broken sublattice symmetry, Dirac-point conductivity...
In this review we discuss the multifaceted problem of spin transport in hydrogenated graphene from a theoretical perspective. The current experimental findings suggest that hydrogenation can either increase or decrease lifetimes, which calls for clarification. We first spin–orbit coupling induced by local re-hybridization and C–H defect formation together with magnetic moment. First-principles calculations unravel strong interplay exchange couplings. concept scattering resonances, recently...
Recent experiments reporting an unexpectedly large spin Hall effect (SHE) in graphene decorated with adatoms have raised a fierce controversy. We apply numerically exact Kubo and Landauer-B\"uttiker formulas to realistic models of gold-decorated disordered (including adatom clustering) obtain the conductivity angle, as well nonlocal resistance quantity accessible experiments. Large angles $\ensuremath{\sim}0.1$ are obtained at zero temperature, but their dependence on clustering differs from...
Many-body interactions in monolayer transition-metal dichalcogenides are strongly affected by their unique band structure. We study these measuring the energy shift of neutral excitons (bound electron-hole pairs) gated ${\mathrm{WSe}}_{2}$ and ${\mathrm{MoSe}}_{2}$. Surprisingly, while blueshift exciton ${X}^{0}$ electron-doped samples can be more than 10 meV, hole-doped is nearly absent. Taking into account dynamical screening local-field effects, we present a transparent analytical model...
Monolayers of semiconducting transition metal dichalcogenides (TMDCs) with unique spin-valley contrasting properties and remarkably strong excitonic effects continue to be a subject intense research interests. These model 2D semiconductors feature two fundamental intravalley excitons species–optically accessible 'bright' anti-parallel spins optically inactive 'dark' parallel spins. For applications exploiting radiative recombination bright or long lifetime dark excitons, it is essential...
Monolayers of transition metal dichalcogenides are ideal materials to control both spin and valley degrees freedom either electrically or optically. Nevertheless, optical excitation mostly generates excitons species with inherently short lifetime spin/valley relaxation time. Here we demonstrate a very efficient pumping resident electrons in n-doped WSe2 WS2 monolayers. We observe that, using continuous wave laser appropriate doping densities, negative trion doublet lines exhibit circular...
The electron valley and spin degree of freedom in monolayer transition-metal dichalcogenides can be manipulated optical transport measurements performed magnetic fields. key parameter for determining the Zeeman splitting, namely separate contribution hole g-factor, is inaccessible most measurements. Here we present an original method that gives access to respective conduction valence band measured splitting. It exploits selection rules exciton complexes, particular ones involving...
In the archetypal monolayer semiconductor WSe_{2}, distinct ordering of spin-polarized valleys (low-energy pockets) in conduction band allows for studies not only simple neutral excitons and charged (i.e., trions), but also more complex many-body states that are predicted at higher electron densities. We discuss magneto-optical measurements electron-rich WSe_{2} monolayers interpret spectral lines emerge high doping as optical transitions six-body exciton ("hexcitons") eight-body...
We present photoluminescence measurements in monolayer WSe$_2$, which point to the importance of interaction between charged particles and excitonic complexes. The theoretical analysis highlights key role played by exchange scattering, referring cases wherein particle composition complex changes after interaction. For example, scattering renders bright complexes dark WSe$_2$ on accounts unique valley-spin configuration this material. In addition ultrafast energy relaxation hot following...
The understanding of spin dynamics and relaxation mechanisms in clean graphene the upper time length scales on which devices can operate are prerequisites to realizing spintronic technologies. Here we theoretically reveal nature fundamental different substrates with spin-orbit Rashba fields as low a few tens micron eV. Spin lifetimes ranging from 50 picoseconds up several nanoseconds found be dictated by substrate-induced electron-hole characteristics. A crossover mechanism Dyakonov-Perel...
We present a method to solve the dynamical Bethe-Salpeter equation numerically. The allows one investigate effects of dielectric screening on spectral position excitons in transition-metal dichalcogenide monolayers. dynamics accounts for response optical phonons materials below and top monolayer electric field lines between electron hole exciton. inclusion this effect unravels origin counterintuitive energy blueshift exciton resonance, observed recently semiconductors that are supported...
We present a theory that studies the state composition of bound exciton in magnetic field. Using basis set made products free electron and hole wavefunctions Landau gauge, we derive secular equation which shows relation between levels (LLs) when is formed. Focusing on excitons light cone, establish scattering selection rule for interaction an LL $n_\text{e}$ with $n_\text{h}$. solve resulting identify simple pairing law, $n_\text{e} = n_\text{h} + l$, informs us construction quantum number...
Just as photons are the quanta of light, plasmons orchestrated charge-density oscillations in conducting media. Plasmon phenomena normal metals, superconductors and doped semiconductors often driven by long-wavelength Coulomb interactions. However, crystals whose Fermi surface is comprised disconnected pockets Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. Here, we show that band structure monolayer...
Photoluminescence experiments from monolayer transition-metal dichalcogenides often show that the binding energy of trions is conspicuously similar to optical phonons. This enigmatic coincidence calls into question whether phonons are involved in radiative recombination process. We address this problem, unraveling an intriguing transition mechanism. Its initial state a localized charge (electron or hole) and delocalized exciton. The final charge, phonon, photon. In between, intermediate...
Monolayer transition-metal dichalcogenides (ML-TMDs) offer exciting opportunities to test the manifestations of many-body interactions through changes in charge density. The two-dimensional character and reduced screening ML-TMDs lead formation neutral charged excitons with binding energies orders magnitude larger than those conventional bulk semiconductors. Tuning density by a gate voltage leads profound optical spectra ML-TMDs. On one hand, increased at large densities should result...