Coupled Ferroelectricity and Superconductivity in Bilayer $T_d$-MoTe$_2

• Main Authors: Jindal, Apoorv, Saha, Amartyajyoti, Li, Zizhong, Taniguchi, Takashi, Watanabe, Kenji, Hone, James C, Birol, Turan, Fernandes, Rafael M, Dean, Cory R, Pasupathy, Abhay N, Rhodes, Daniel A
• Format: Journal Article
• Language: English
• Published: 11-04-2023
• Subjects: Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Physics - Superconductivity
• DOI: 10.48550/arxiv.2304.05443

Nature 613, 48-52 (2023) Achieving electrostatic control of quantum phases is at the frontier of
condensed matter research. Recent investigations have revealed
superconductivity tunable by electrostatic doping in twisted graphene
heterostructures and in two-dimensional (2D) semimetals such as WTe$_2$. Some
of these systems have a polar crystal structure that gives rise to
ferroelectricity, in which the interlayer polarization exhibits bistability
driven by external electric fields. Here we show that bilayer $T_d$-MoTe$_2$
simultaneously exhibits ferroelectric switching and superconductivity.
Remarkably, a field-driven, first-order superconductor-to-normal transition is
observed at its ferroelectric transition. Bilayer $T_d$-MoTe$_2$ also has a
maximum in its superconducting transition temperature ($T_\textrm{c}$) as a
function of carrier density and temperature, allowing independent control of
the superconducting state as a function of both doping and polarization. We
find that the maximum $T_\textrm{c}$ is concomitant with compensated electron
and hole carrier densities and vanishes when one of the Fermi pockets
disappears with doping. We argue that this unusual polarization-sensitive 2D
superconductor is driven by an interband pairing interaction associated with
nearly nested electron and hole Fermi pockets.