Direct measurement of ferroelectric polarization in a tunable semimetal

Sergio C. Barrera, Qingrui Cao, Yang Gao, Yuan Gao, Vineetha S. Bheemarasetty, Jiaqiang Yan, David G. Mandrus, Wenguang Zhu, Di Xiao and Benjamin M. Hunt ()
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Sergio C. Barrera: Carnegie Mellon University
Qingrui Cao: Carnegie Mellon University
Yang Gao: Carnegie Mellon University
Yuan Gao: Carnegie Mellon University
Vineetha S. Bheemarasetty: Carnegie Mellon University
Jiaqiang Yan: Oak Ridge National Laboratory
David G. Mandrus: Oak Ridge National Laboratory
Wenguang Zhu: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China
Di Xiao: Carnegie Mellon University
Benjamin M. Hunt: Carnegie Mellon University

Nature Communications, 2021, vol. 12, issue 1, 1-9

Abstract: Abstract Ferroelectricity, the electrostatic counterpart to ferromagnetism, has long been thought to be incompatible with metallicity due to screening of electric dipoles and external electric fields by itinerant charges. Recent measurements, however, demonstrated signatures of ferroelectric switching in the electrical conductance of bilayers and trilayers of WTe2, a semimetallic transition metal dichalcogenide with broken inversion symmetry. An especially promising aspect of this system is that the density of electrons and holes can be continuously tuned by an external gate voltage. This degree of freedom enables measurement of the spontaneous polarization as free carriers are added to the system. Here we employ capacitive sensing in dual-gated mesoscopic devices of bilayer WTe2 to directly measure the spontaneous polarization in the metallic state and quantify the effect of free carriers on the polarization in the conduction and valence bands, separately. We compare our results to a low-energy model for the electronic bands and identify the layer-polarized states that contribute to transport and polarization simultaneously. Bilayer WTe2 is thus shown to be a fully tunable ferroelectric metal and an ideal platform for exploring polar ordering, ferroelectric transitions, and applications in the presence of free carriers.

Date: 2021
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DOI: 10.1038/s41467-021-25587-3

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