Can trions crystallize in TMDC monolayers?

Positively and negatively charged trions in monolayers of transition metal dichalcogenides (TMD) are bound with binding energies of 20-30 meV [1]. Based on the existence of the trions in TMD monolayers, one can propose that a dilute gas of trions, as composite fermions, forms a 2D Wigner crystal. This is similar to the 2D Wigner crystal formed by a dilute system of electrons. The formation of 2D Wigner crystal of the dilute system of trions in TMDC monolayers is studied. We show how the reduction of dimensionality affects the binding energy of trions and their crystallization in TMD monolayers. The 2D trion gas in TMD is described using a Charge–Charge, Charge-Exciton, Exciton-Exciton interactions based on the screened Coulomb interaction - Keldysh potential [2]. The formation of the 2D Wigner crystal in the dilute system of trions in TMD monolayers, when the average distance between the trions is much larger than the radius of each trion is predicted. It is shown that the critical density of the formation of the trion Wigner crystal is greater than the critical density of the electron Wigner crystal in the same material.

[1] R.Ya. Kezerashvili, Few-Body Syst. 60, 52 (2019)
[2] L.V. Keldysh, JETP Lett. 29, 658 (1979)