Metal-Insulator Transition and High Temperature Charge Density Waves in monolayer VSe2

Although emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed, such interface-driven phenomena in shaping the electronic properties has not been well established in van der Waals heterointerfaces. By diminishing the material thickness and forming a heterointerface, we observed two types of charge-ordering transitions in monolayer VSe₂ on graphene substrates. Comprehensive combination of ARPES, STM, and renormalization group analysis enable us to reveal the low-dimensionality and the heterointerface play important roles in enhancing charge density wave temperature to 350 K contrasted to the 105 K in bulk VSe₂ and in driving the unexpected metal-insulator transition at 135 K in the family of monolayered transition metal dichalcogenides. We will discuss implications of our observations in comparison with the similar results reported by two other groups.

This work is published in Nano Letters 18, 5432 (2018). This work was supported by the Korean government (No. NRF-2009-0093818, NRF-2014R1A4A1071686, NRF-2015R1D1A1A01057271, NRF-2017R1C1B2004927, NRF-2015R1C1A1A01051629, No. 2011-0030046, and Grant No. IBS-R009-G1). The ALS is supported by the U.S. DOE under Contract No. DE-AC02- 05CH11231.