2016/04/04 by Ruixiang Fei, Wei Kang, Li Yang
Physics and Astronomy · #cond-mat.mtrl-sci #cond-mat.mes-hall #cond-mat.stat-mech #physics.comp-ph
paper · pdf · doi:10.1103/physrevlett.117.097601
published as Phys. Rev. Lett. 117, 097601 (2016) · 5 pages with 4 figures
arxiv created 2016/04/04 · arxiv updated 2016/08/31
Ferroelectricity usually fades away when materials are thinned down below a critical value. Employing the first-principles density functional theory and modern theory of polarization, we show that the unique ionic-potential anharmonicity can induce spontaneous in-plane electrical polarizations and ferroelectricity in monolayer group-IV monochalcogenides MX (M=Ge, Sn; X=S, Se). Using Monte Carlo simulations with an effective Hamiltonian extracted from the parameterized energy space, we show these materials exhibit a two-dimensional ferroelectric phase transition that is described by fourth-order Landau theory. We also show the ferroelectricity in these materials is robust and the corresponding Curie temperature is higher than room temperature, making these materials promising for realizing ultra-thin ferroelectric devices of broad interest.