Interlayer excitons in a bulk van der Waals semiconductor

Abstract

Bound electron–hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose–Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe2, we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.

Fine structure of K-excitons in multilayers of transition metal dichalcogenides

“…3 and 6), are assigned to the pair of intra-(X A ) and interlayer (X ′ A ) A-excitons, and to the analogous pair of intra-(X B ) and interlayer (X ′ B ) Bexcitons. We use the signs and magnitude of the exciton g-factors as fingerprints the intra-and interlayer nature of the X A -and X ′ A -excitons respectively [39]. Namely, we conclude that g XA ≈ −4, while g X ′ A ≈ 8.…”

Hidden spin-polarized bands in semiconducting 2H-MoTe2

“…For instance, the A* feature, which is ≈ 50 meV above the A transition, has been either assigned to excited excitonic states [10,11] or direct transitions at the H k-point [12][13][14]. More recently magneto-reflectance measurements showed that such feature could be attributed to an interlayer excitonic transition [15,16]. Hence it is desirable to further investigate the excitonic features present in MX 2 to better understand the effect of the SOC on the electronic band structure.…”

Superradiant coupling effects in transition-metal dichalcogenides

“…The near-K -point bands have a flat dispersion along the K − H axis, indicating that even in a multilayer structure, the corresponding quasi-particles are strongly confined within the individual layers and can be considered as effectively two-dimensional. Indeed, recent theoretical and experimental studies attribute the excitonic series in TMDC multilayer systems as being due to quasi twodimensional intra-and interlayer excitons [2,3].…”