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Radiative lifetime of localized excitons in transition-metal dichalcogenides
摘要： Disorder derived from defects or local strain in monolayer transition-metal dichalcogenides (TMDs) can lead to a dramatic change in the physical behavior of the interband excitations, producing inhomogeneous spectral broadening and localization leading to radiative lifetime increase. In this study, we have modeled the surface disorder of a monolayer TMD sample through a randomized potential in the layer plane. We show that this model, applied to a monolayer of WSe2, allows us to simulate the spectra of localized exciton states as well as their radiative lifetime. In this context, we give an in depth study of the in?uence of the disorder potential parameters on the optical properties of these defects through energies, density of states, oscillator strengths, photoluminescence (PL) spectroscopy, and radiative lifetime at low temperature (4 K). We demonstrate that localized excitons have a longer emission time than free excitons, in the range of tens of picoseconds or more, the radiative decay time depending strongly on the disorder parameter and dielectric environment. Finally, in order to prove the validity of our model, we compare it to available experimental results of the literature.
关键词： disorder potential,localized excitons,radiative lifetime,transition-metal dichalcogenides,photoluminescence spectroscopy
更新于2025-09-09 09:28:46
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Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators
摘要： In an ultrathin topological insulator (TI) ?lm, a hybridization gap opens in the TI surface states, and the system is expected to become either a trivial insulator or a quantum spin Hall insulator when the chemical potential is within the hybridization gap. Here we show, however, that these insulating states are destroyed by the presence of a large and long-range-correlated disorder potential, which converts the expected insulator into a metal. We perform transport measurements in ultrathin dual-gated topological insulator ?lms as a function of temperature, gate voltage, and magnetic ?eld, and we observe a metalliclike nonquantized conductivity, which exhibits a weak antilocalizationlike cusp at low magnetic ?elds and gives way to a nonsaturating linear magnetoresistance at large ?elds. We explain these results by considering the disordered network of electron- and hole-type puddles induced by charged impurities. We argue theoretically that such disorder can produce an insulator-to-metal transition as a function of increasing disorder strength, and we derive a condition on the band gap and the impurity concentration necessary to observe the insulating state. We also explain the linear magnetoresistance in terms of strong spatial ?uctuations of the local conductivity using both numerical simulations and a theoretical scaling argument.
关键词： disorder potential,hybridization gap,magnetotransport,linear magnetoresistance,topological insulator
更新于2025-09-04 15:30:14