Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65?Tesla.

ABSTRACT: In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS2 and MoS2 in high magnetic fields to 65?T. Both the A and B excitons exhibit similar Zeeman splittings of approximately -230??eV?T(-1) (g-factor ?-4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS2, from which radii of ?1.53 and ?1.16?nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470?meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). These results highlight the utility of high magnetic fields for understanding new two-dimensional materials.

SUBMITTER: Stier AV 

PROVIDER: S-EPMC4748133 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature