Devices*

          Recently, ionic gating was expanded to intercalation of alkali metals into the vdW gaps of layered 2D materials, and a variety of gate-controlled quantum phases have been reported, as exemplified by the room temperature ferromagnetism in Li-intercalated Fe₃GeTe₂¹, BCS-BEC crossover in Li_xZrNCl², and FFLO state in LixMoS2³. Here we report the gate-controlled K intercalation of MoS₂ using Hall transport experimentation and describe a systematic evolution of low temperature phases.

          Resistivity is continuously reduced, showing a metallic behavior without superconductivity in the 2H phase. At V_G ~ 3 V, a dramatic resistivity drop occurs concurrently with a one order of magnitude carrier density decrease, indicating a transition from 2H to 1T’ structure.  Superconductivity of T_c = 5.5 K appears in the high carrier density 1T’ state. With further increased carrier density, the metallic state without superconductivity emerges.  During the deintercalation process, the phase apparently stays in the 1T’ structure and exhibits a metal-insulator transition. The present results indicate that K-intercalation exhibits a totally different phase diagram from that for the electrostatically doped MoS₂⁴.

 

¹Y. Deng et al. Nature 563, 94 (2018).

²Y. Nakagawa et al., Science 372, 190 (2021).

³D. Zhao et al., Nat. Phys. (2023) https://doi.org/10.1038/s41567-023-02202-4

⁴ J. T. Ye et al., Science 338, 1193 (2012).