Identifying the Transition Order in an Artificial Ferroelectric van der Waals Heterostructure.

Two-dimensional semiconducting ferroelectrics can enable new technology for low-energy electronic switching. However, conventional ferroelectric materials are usually electrically insulating and suffer from severe depolarization effects when downscaled to atomic thickness. Following recent work, we show that robust ferroelectricity can be obtained from nonferroelectric semiconducting 2H-WSe by creating R-stacked bilayers with broken inversion symmetry. Here, we identify that the phase transition order of this artificial ferroelectric heterostructure is first-order, with a discontinuous jump in the order parameter across the phase transition temperature. The Curie temperature has been experimentally determined as 353 K. Using the Landau-Devonshire theory, we further determine the Curie-Weiss temperatures to be 351.2 K. We additionally demonstrate the robustness of this artificial ferroelectric material using consecutive polarization measurements, where no appreciable deterioration was detected.