Structural Phase Transition and Material Properties of Few-Layer Monochalcogenides

Mehrshad Mehboudi, Benjamin M. Fregoso, Yurong Yang, Wenjuan Zhu, Arend van der Zande, Jaime Ferrer, L. Bellaiche, Pradeep Kumar, and Salvador Barraza-Lopez
Phys. Rev. Lett. 117, 246802 – Published 9 December 2016
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Abstract

GeSe and SnSe monochalcogenide monolayers and bilayers undergo a two-dimensional phase transition from a rectangular unit cell to a square unit cell at a critical temperature Tc well below the melting point. Its consequences on material properties are studied within the framework of Car-Parrinello molecular dynamics and density-functional theory. No in-gap states develop as the structural transition takes place, so that these phase-change materials remain semiconducting below and above Tc. As the in-plane lattice transforms from a rectangle into a square at Tc, the electronic, spin, optical, and piezoelectric properties dramatically depart from earlier predictions. Indeed, the Y and X points in the Brillouin zone become effectively equivalent at Tc, leading to a symmetric electronic structure. The spin polarization at the conduction valley edge vanishes, and the hole conductivity must display an anomalous thermal increase at Tc. The linear optical absorption band edge must change its polarization as well, making this structural and electronic evolution verifiable by optical means. Much excitement is drawn by theoretical predictions of giant piezoelectricity and ferroelectricity in these materials, and we estimate a pyroelectric response of about 3×1012C/Km here. These results uncover the fundamental role of temperature as a control knob for the physical properties of few-layer group-IV monochalcogenides.

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  • Received 18 January 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.246802

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & ThermodynamicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Mehrshad Mehboudi1, Benjamin M. Fregoso2, Yurong Yang1, Wenjuan Zhu3, Arend van der Zande4, Jaime Ferrer5, L. Bellaiche1, Pradeep Kumar1, and Salvador Barraza-Lopez1,*

  • 1Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
  • 2Department of Physics, University of California, Berkeley, California 94720, USA
  • 3Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
  • 4Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
  • 5Departamento de Física, Universidad de Oviedo, 33007 Oviedo, Spain

  • *sbarraza@uark.edu

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Issue

Vol. 117, Iss. 24 — 9 December 2016

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