Abstract
We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valley-polarized holes in the presence of a strong magnetic field. We find that exciton-hole interactions manifest themselves in hole-density dependent, Shubnikov-de Haas-like oscillations in the energy and line broadening of the excitonic resonances. These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, thus demonstrating that strong interactions between the excitons and Landau-quantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides.
Highlights
Optical excitations of a semiconductor hosting a twodimensional electron (2DES) or hole (2DHS) system subjected to a strong magnetic field provide a direct tool for investigating quantum-Hall states arising from Landau-level (LL) quantization of the carrier orbital motion [1,2,3]
We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valleypolarized holes in the presence of a strong magnetic field
These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, demonstrating that strong interactions between the excitons and Landauquantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides
Summary
With LL filling, providing a first direct evidence for the influence of quantum-Hall states on the excitonic excitations in a TMD monolayer. We present the data acquired for one of these devices [Fig. 1(a)], where density-dependent oscillations are manifest in the hole-doped regime; while all three devices show such oscillations in the presence of a 2DHS, the third device, described in the Supplemental Material [36], displays analogous oscillations for a 2DES. The valley-selective optical response of all samples has been analyzed by means of low-temperature (T ≈ 4 K), circular polarizationresolved, white light reflection magneto-spectroscopy (for details, see Supplemental Material [36]). For − 7V ≲ Vg ≲ 4 V, when the sample is devoid of free carriers, the spectrum features only the bare exciton resonance. Once Vg is increased (decreased) beyond this range, free electrons (holes) start to be injected to the monolayer. As demonstrated previously [32,33,34,35], the attractive interaction between these carriers and the excitons dress the latter into exciton-polarons, which in turn qualitatively alters the nature of the optical transitions
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