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This content will become publicly available on July 23, 2019

Title: Ferroelectric switching of a two-dimensional metal

A ferroelectric is a material with a polar structure whose polarity can be reversed (switched) by applying an electric field. In metals, itinerant electrons screen electrostatic forces between ions, which explains in part why polar metals are very rare. Screening also excludes external electric fields, apparently ruling out the possibility of ferroelectric switching. However, in principle, a thin enough polar metal could be sufficiently penetrated by an electric field to have its polarity switched. In this paper we show that the topological semimetal WTe 2 provides an embodiment of this principle. Although monolayer WTe 2 is centro-symmetric and thus non-polar, the stacked bulk structure is polar. We find that two- or three-layer WTe 2 exhibits spontaneous out-of-plane electric polarization that can be switched using gate electrodes. We directly detect and quantify the polarization using graphene as an electric-field sensor. Moreover, the polarization states can be differentiated by conductivity and the carrier density can be varied to modify the properties. Finally, the temperature at which polarization vanishes is above 350 kelvin, and even when WTe 2 is sandwiched between graphene layers it retains its switching capability at room temperature, demonstrating a robustness suitable for applications in combination with other two-dimensional materials.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Univ. of Washington, Seattle, WA (United States). Dept. of Physics
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  4. Univ. of Washington, Seattle, WA (United States). Dept. of Physics. Dept. of Materials Science and Engineering
Publication Date:
Grant/Contract Number:
AC05-00OR22725; SC0002197; SC0018171; DMR-1420451; FA9550-14-1-0277; EFRI 2DARE 1433496; MRSEC 1719797
Type:
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Washington, Seattle, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ferroelectrics and multiferroics; two-dimensional materials
OSTI Identifier:
1462831