Robust two-dimensional ferroelectricity in single-layer γ-SbP and γ-SbAs

Currently, two-dimensional ferroelectricity has attracted considerable attention due to its fascinating properties and promising applications. Herein, by means of first-principles calculations, we propose a series of excellent ferroelectric materials, single-layer gamma-SbX (X = As, P). Both systems exhibit excellent 2D ferroelectricity with an in-plane spontaneous polarization around 3.80 x 10(-10) C m(-1) (gamma-SbAs) and 3.47 x 10(-10) C m(-1) (gamma-SbP). More importantly, the ferroelectricity of SL gamma-SbAs (gamma-SbP) has been maintained well at 700 K (600 K), much higher than room temperature. These properties indicate that SL gamma-SbX are robust ferroelectric materials, which could be promising for nonvolatile memory devices and nanoscale electronics. The Landau theory is employed to explain the mechanism of the ferroelectric phase transition, which provides a better understanding of the universal critical properties of 2D materials.