First-principles study of CuInP₂S₆ based van der Walls heterostructure at non-equilibrium state

The discovery of polarization switching in two-dimensional (2D) van der Waals (vdW) materials such as copper indium thiophosphate (CuInP₂S₆) has led to the development of ultrathin ferroelectric devices. However, the atomistic-level description of the switching process is still mostly limited to equilibrium first-principles methods, thereby lacking a direct connection to the experimental measurements. In this presentation, carrying out the recently developed multi-space constrained-search density functional theory (MS-DFT) [1], we study the polarization switching mechanism of CuInP₂S₆ on the electrified electrode surface under a finite bias. Taking the advantages of MS-DFT in which total energies are variationally calculated under finite-bias, we quantitatively provide the bias-dependent free energy and polarization profile by calculating the electric enthalpy. We also calculate the quantum transport properties of the vdW heterostructure composed of CuInP₂S₆ as a channel material sandwiched by various electrode materials and provide design guidelines for the development of advanced ferroelectric material-based nanodevices.

[1] J. Lee, H. Yeo, and Y.-H. Kim, Proc. Nat. Acad. Sci. 117(19), 10142-10148 (2020); J.Lee, H.S.Kim, and Y.-H. Kim, Adv. Sci. 7, 2001038 (2020)