Valley-Dependent Interlayer Excitons in Magnetic WSe<sub>2</sub>/CrI<sub>3</sub>.

Heißenbüttel, Marie-Christin; Deilmann, Thorsten; Krüger, Peter; Rohlfing, Michael · Nano Lett · 2021

basic_science · Level V

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Abstract

Heterostructures of two-dimensional transition-metal dichalcogenides and ferromagnetic substrates are important candidates for the development of viable new spin- or valleytronic devices. For the prototypical bilayer of WSe<sub>2</sub> on top of a ferromagnetic layer of CrI<sub>3</sub>, we find substantially different coupling of both WSe<sub>2</sub> K-valleys to the sublayer. Besides an energy splitting of a few meV, the corresponding excitons have significantly different interlayer character with charge transfer allowed at the K̅<sup>-</sup> point but forbidden at K̅<sup>+</sup>. The different exciton wave functions result in a distinctly different response to magnetic fields with <i>g</i> factors of about -4.4 and -4.0, respectively. By means of ab initio <i>GW</i>/Bethe-Salpeter equation calculations, these findings establish <i>g</i> factors as tool for investigating the exciton character and shedding light on the detailed quantum-mechanical interplay of magnetic and optical properties which are essential for the targeted development of optoelectronic devices.