Electric-field tunable fine-structure splitting in monolayer semiconductors

Semiconducting quantum dots (QDs) are among the most promising source of on-demand, indistinguishable single and entangled photon source which are the basic ingredients for quantum communications and computing applications¹. The most common approach to generate entangled photon pairs in QDs is to utilize the biexciton to exciton radiative cascade². Recently, single confined exciton and biexciton emission have been demonstrated at locally strained sites in semiconducting two-dimensional (2D) materials^3-5. The 2D host makes them ideal for integrated quantum photonics studies. However, a sizable fine-structure splitting (FSS) (~800 ueV) due to anisotropic electron-hole exchange interaction in these quantum-confined excitons and biexcitons poses a limit to the indistinguishability of the generated photon pairs. We demonstrate a suppression of the FSS by leveraging on van der Waals heterostructure and fabricate a voltage tunable device to minimize the effect of exchange interaction.
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2. Nat. Phy. 6, 947 (2010)
3. Nat. Nano. 10, 507 (2015)
4. Nat. Comm. 8, 15093 (2017)
5. Nat, Comm. 7, 13409 (2016)