Topology of atomically thin soft ferroelectric membranes at finite temperature

Abstract

One account of two-dimensional (2D) structural transformations in 2D ferroelectrics predicts an evolution from a structure with Pnm2${}_1$ symmetry into a structure with square P4/nmm symmetry and is consistent with experimental evidence, while another argues for a transformation into a structure with rectangular Pnmm symmetry. An analysis of the assumptions made in these models is provided here, and six fundamental results concerning these transformations are contributed as follows: (i) Softened phonon modes produce rotational modes in these materials. (ii) The transformation to a structure with P4/nmm symmetry occurs at the lowest critical temperature $T_c$. (iii) The hypothesis that one unidirectional optical vibrational mode underpins the 2D transformation is unwarranted. (iv) Being successively more constrained, a succession of critical temperatures ($T_c<T_c^{\prime }<T_c^{\prime \prime }$) occurs in going from molecular dynamics calculations with the NPT and NVT ensembles onto the model with unidirectional oscillations. (v) The choice of exchange-correlation functional impacts the estimate of the critical temperature. (vi) Crucially, the correct physical picture of these transformations is one in which rotational modes confer a topological character to the 2D transformation via the proliferation of vortices.

arXiv commentOriginally submitted on August 27, 2019

References in corpus (13)

• The SIESTA method for ab initio order-N materials simulation
• Efficient index handling of multidimensional periodic boundary conditions
• Efficient implementation of a van der Waals density functional: Application to double-wall carbon nanotubes
• Giant Piezoelectricity in Monolayer Group IV Monochalcogenides: SnSe, SnS, GeSe and GeS
• Robust Ferroelectricity in Monolayer Group-IV Monochalcogenides
• An exchange functional that tests the robustness of the plasmon description of the van der Waals density functional
• Valleytronics in Tin (II) Sulfide
• Structural phase transition and material properties of few-layer monochalcogenides
• Two-dimensional disorder in black phosphorus and monochalcogenide monolayers
• Tuning the ferro- to para-electric transition temperature and dipole orientation of group-IV monochalcogenide monolayers
• In-Plane Ferroelectric Tunnel Junction
• Strong second harmonic generation in two-dimensional ferroelectric IV-monochalcogenides
• Group-IV monochalcogenide monolayers: two-dimensional ferroelectrics with weak intra-layer bonds and a phosphorene-like monolayer dissociation energy

Cited by in corpus (8)

• Colloquium: Physical properties of group-IV monochalcogenide monolayers
• Ultralow thermal conductivity in two-dimensional MoO${}_3$
• Metastable piezoelectric group IV monochalcogenide monolayers with a buckled honeycomb structure
• Thermoelectricity of Tin Selenide Monolayers Across a Structural Phase Transition
• Berezinskii-Kosterlitz-Thouless Phase in Two-dimensional Ferroelectrics
• Slippery paraelectric transition metal dichalcogenide bilayers
• Elasticity of 2D ferroelectrics across their paraelectric phase transformation
• Tuning energy barriers by doping 2D group-IV monochalcogenides