WTe2

/Tag: WTe2

An ultrafast symmetry switch in a Weyl semimetal

2019-01-02T18:33:47+00:00January 2nd, 2019|Categories: Publications|Tags: |

An ultrafast symmetry switch in a Weyl semimetalAn ultrafast symmetry switch in a Weyl semimetal, Published online: 02 January 2019; doi:10.1038/s41586-018-0809-4Terahertz light pulses induce transitions between a topological and a trivial phase in the Weyl semimetal WTe2 through an interlayer shear strain.

Published in: "Nature".

In‐Plane Anisotropic Thermal Conductivity of Few‐Layered Transition Metal Dichalcogenide Td‐WTe2

2019-01-01T22:34:33+00:00January 1st, 2019|Categories: Publications|Tags: |

In‐plane anisotropic thermal conductivities are experimentally demonstrated in suspended Td‐WTe2 of different thicknesses. Theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As the thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in the stronger anisotropy. Abstract 2D Td‐WTe2 has attracted increasing attention due to its promising applications in spintronic, field‐effect chiral, and high‐efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in‐plane anisotropic thermal conductivities in suspended Td‐WTe2 samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides. The results reveal an obvious anisotropy in the thermal conductivities between the zigzag and armchair axes. The theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in stronger anisotropy. The findings here are crucial for developing efficient thermal management schemes when engineering thermal‐related applications of a 2D system.

Published in: "Advanced Materials".

In‐Plane Anisotropic Thermal Conductivity of Few‐Layered Transition Metal Dichalcogenide Td‐WTe2

2018-12-29T22:35:20+00:00December 29th, 2018|Categories: Publications|Tags: |

In‐plane anisotropic thermal conductivities are experimentally demonstrated in suspended Td‐WTe2 of different thicknesses. Theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As the thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in the stronger anisotropy. Abstract 2D Td‐WTe2 has attracted increasing attention due to its promising applications in spintronic, field‐effect chiral, and high‐efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in‐plane anisotropic thermal conductivities in suspended Td‐WTe2 samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides. The results reveal an obvious anisotropy in the thermal conductivities between the zigzag and armchair axes. The theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in stronger anisotropy. The findings here are crucial for developing efficient thermal management schemes when engineering thermal‐related applications of a 2D system.

Published in: "Advanced Materials".

In‐Plane Anisotropic Thermal Conductivity of Few‐Layered Transition Metal Dichalcogenide Td‐WTe2

2018-12-28T08:34:21+00:00December 28th, 2018|Categories: Publications|Tags: |

In‐plane anisotropic thermal conductivities are experimentally demonstrated in suspended Td‐WTe2 of different thicknesses. Theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As the thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in the stronger anisotropy. Abstract 2D Td‐WTe2 has attracted increasing attention due to its promising applications in spintronic, field‐effect chiral, and high‐efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in‐plane anisotropic thermal conductivities in suspended Td‐WTe2 samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides. The results reveal an obvious anisotropy in the thermal conductivities between the zigzag and armchair axes. The theoretical calculation implies that the in‐plane anisotropy is attributed to the different mean free paths along the two orientations. As thickness decreases, the phonon‐boundary scattering increases faster along the armchair direction, resulting in stronger anisotropy. The findings here are crucial for developing efficient thermal management schemes when engineering thermal‐related applications of a 2D system.

Published in: "Advanced Materials".

Spontanous breaking of time-reversal symmetry at the edges of 1T’ monolayer transition metal dichalcogenides. (arXiv:1812.09082v1 [cond-mat.mes-hall])

2018-12-24T02:29:29+00:00December 24th, 2018|Categories: Publications|Tags: , , |

Using density functional theory calculations and the Greens’s function formalism, we report the existence of magnetic edge states with a non-collinear spin texture present on different edges of the 1T’ phase of the three monolayer transition metal dichalcogenides (TMDs): MoS2, MoTe2 and WTe2. The magnetic states are gapless and accompanied by a spontaneous breaking of the time-reversal symmetry. This may have an impact on the prospects of utilizing WTe2 as a quantum spin Hall insulator. It has previously been suggested that the topologically protected edge states of the 1T’ TMDs could be switched off by applying a perpendicular electric field. We confirm with fully self-consistent DFT calculations, that the topological edge states can be switched off. The investigated magnetic edge states are seen to be robust and remains gapless when applying a field.

Published in: "arXiv Material Science".

Intrinsic Spin Hall Conductivity of MoTe2 and WTe2 Semimetals. (arXiv:1812.06910v1 [cond-mat.mtrl-sci])

2018-12-18T02:29:22+00:00December 18th, 2018|Categories: Publications|Tags: , , |

We report a comprehensive study on the intrinsic spin Hall conductivity (SHC) of semimetals MoTe2 and WTe2 by ab initio calculation. Large SHC and desirable spin Hall angles have been discovered, due to the strong spin orbit coupling effect and low charge conductivity in semimetals. Diverse anisotropic SHC values, attributed to the unusual reduced-symmetry crystalline structure, have been revealed. We report an effective method on SHC optimization by electron doping, and exhibit the mechanism of SHC variation respect to the energy shifting by the spin Berry curvature. Our work provides insights into the realization of strong spin Hall effects in 2D systems.

Published in: "arXiv Material Science".

Observation of the nonlinear Hall effect under time-reversal-symmetric conditions

2018-12-17T16:35:06+00:00December 17th, 2018|Categories: Publications|Tags: |

Observation of the nonlinear Hall effect under time-reversal-symmetric conditionsObservation of the nonlinear Hall effect under time-reversal-symmetric conditions, Published online: 17 December 2018; doi:10.1038/s41586-018-0807-6The nonlinear Hall effect is observed in bilayer WTe2 in the absence of a magnetic field, providing a direct measure of the dipole moment of the Berry curvature.

Published in: "Nature".

Van der Waals Heteroepitaxial Growth of Monolayer Sb in a Puckered Honeycomb Structure

2018-12-15T22:33:29+00:00December 15th, 2018|Categories: Publications|Tags: , |

Monolayer α‐phase antimonene, a structural analog to black phosphorous, is fabricated on a WTe2 substrate. The α‐antimonene exhibits great stability upon exposure to air. Its electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make α‐antimonene promising in the future electronic applications. Abstract Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. Monolayers of α‐phase Sb (α‐antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging. Here, high‐quality monolayerα‐antimonene is successfully grown, with the thickness finely controlled. The α‐antimonene exhibits great stability upon exposure to air. Combining scanning tunneling microscopy, density functional theory calculations, and transport measurements, it is found that the electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make the α‐antimonene promising for future electronic applications.

Published in: "Advanced Materials".

Anomalous and Polarization‐Sensitive Photoresponse of Td‐WTe2 from Visible to Infrared Light

2018-12-15T22:33:25+00:00December 15th, 2018|Categories: Publications|Tags: |

Semimetal Td‐WTe2 demonstrates broadband anomalous and polarization‐sensitive photoresponse. The giant photocurrent and responsivity reach 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K, and the photocurrent anisotropic ratio of 4.9 for a 514.5 nm laser. Consistently, first‐principles calculations confirm angle sensitive bandgap opening of WTe2 by polarized light, showing its photodetection potential. Abstract Recently, an emergent layered material Td‐WTe2 was explored for its novel electron–hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe2 flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid‐ and far‐infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light‐induced surface bandgap opening from the first‐principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K. Furthermore, the WTe2 anomalous photocurrent matches its in‐plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first‐principles calculations confirm the angle‐dependent bandgap opening of WTe2 under polarized light irradiation. The anomalous and polarization‐sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe2 surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.

Published in: "Advanced Materials".

Van der Waals Heteroepitaxial Growth of Monolayer Sb in a Puckered Honeycomb Structure

2018-12-13T00:34:12+00:00December 12th, 2018|Categories: Publications|Tags: , |

Monolayer α‐phase antimonene, a structural analog to black phosphorous, is fabricated on a WTe2 substrate. The α‐antimonene exhibits great stability upon exposure to air. Its electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make α‐antimonene promising in the future electronic applications. Abstract Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. Monolayers of α‐phase Sb (α‐antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging. Here, high‐quality monolayerα‐antimonene is successfully grown, with the thickness finely controlled. The α‐antimonene exhibits great stability upon exposure to air. Combining scanning tunneling microscopy, density functional theory calculations, and transport measurements, it is found that the electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make the α‐antimonene promising for future electronic applications.

Published in: "Advanced Materials".

Anomalous and Polarization‐Sensitive Photoresponse of Td‐WTe2 from Visible to Infrared Light

2018-12-13T00:33:58+00:00December 12th, 2018|Categories: Publications|Tags: |

Semimetal Td‐WTe2 demonstrates broadband anomalous and polarization‐sensitive photoresponse. The giant photocurrent and responsivity reach 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K, and the photocurrent anisotropic ratio of 4.9 for a 514.5 nm laser. Consistently, first‐principles calculations confirm angle sensitive bandgap opening of WTe2 by polarized light, showing its photodetection potential. Abstract Recently, an emergent layered material Td‐WTe2 was explored for its novel electron–hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe2 flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid‐ and far‐infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light‐induced surface bandgap opening from the first‐principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K. Furthermore, the WTe2 anomalous photocurrent matches its in‐plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first‐principles calculations confirm the angle‐dependent bandgap opening of WTe2 under polarized light irradiation. The anomalous and polarization‐sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe2 surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.

Published in: "Advanced Materials".

Observation of Spin Hall Effect in Semimetal WTe2. (arXiv:1812.02113v1 [cond-mat.mes-hall])

2018-12-06T02:29:14+00:00December 6th, 2018|Categories: Publications|Tags: , , |

Discovery of two-dimensional (2D) topological semimetals has revealed the opportunities to realize several extraordinary physical phenomena in condensed matter physics. Specifically, these semimetals with strong spin-orbit coupling, novel spin texture, and broken inversion symmetry are predicted to exhibit a large spin Hall effect that can efficiently convert the charge current to a spin current. Here for the first time, we report the direct experimental observation of a large and gate-controlled spin Hall and inverse spin Hall effects in a layered semimetal WTe2 at room temperature obeying Onsager reciprocity relation. We demonstrate the creation and detection of the pure spin current generated by spin Hall phenomenon in WTe2 by making van der Waals heterostructures with graphene, taking advantage of its long spin coherence length and a large spin transmission efficiency at the heterostructure interface. A large and gate-tunable spin Hall signal has been observed with spin Hall angle up to 0.37 and a spin Hall resistivity r{ho}SH= 3.29 x10-4 {Omega}.cm at room temperature which is almost one to two orders of magnitude larger than that of the conventional heavy metals. These experimental findings well supported by ab initio calculations; pave the way for utilization of gate tunable spin-orbit induced phenomena in 2D material heterostructures for spin-based device architectures.

Published in: "arXiv Material Science".

Anomalous and Polarization‐Sensitive Photoresponse of Td‐WTe2 from Visible to Infrared Light

2018-12-05T18:34:39+00:00December 5th, 2018|Categories: Publications|Tags: |

Semimetal Td‐WTe2 demonstrates broadband anomalous and polarization‐sensitive photoresponse. The giant photocurrent and responsivity reach 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K, and the photocurrent anisotropic ratio of 4.9 for a 514.5 nm laser. Consistently, first‐principles calculations confirm angle sensitive bandgap opening of WTe2 by polarized light, showing its photodetection potential. Abstract Recently, an emergent layered material Td‐WTe2 was explored for its novel electron–hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe2 flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid‐ and far‐infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light‐induced surface bandgap opening from the first‐principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K. Furthermore, the WTe2 anomalous photocurrent matches its in‐plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first‐principles calculations confirm the angle‐dependent bandgap opening of WTe2 under polarized light irradiation. The anomalous and polarization‐sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe2 surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.

Published in: "Advanced Materials".

Van der Waals Heteroepitaxial Growth of Monolayer Sb in a Puckered Honeycomb Structure

2018-12-05T18:34:36+00:00December 5th, 2018|Categories: Publications|Tags: , |

Monolayer α‐phase antimonene, a structural analog to black phosphorous, is fabricated on a WTe2 substrate. The α‐antimonene exhibits great stability upon exposure to air. Its electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make α‐antimonene promising in the future electronic applications. Abstract Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. Monolayers of α‐phase Sb (α‐antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging. Here, high‐quality monolayerα‐antimonene is successfully grown, with the thickness finely controlled. The α‐antimonene exhibits great stability upon exposure to air. Combining scanning tunneling microscopy, density functional theory calculations, and transport measurements, it is found that the electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make the α‐antimonene promising for future electronic applications.

Published in: "Advanced Materials".

Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1<i>T</i>’-WTe<sub>2</sub>

2018-10-04T10:33:25+00:00October 4th, 2018|Categories: Publications|Tags: |

Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1T’-WTe2Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1<i>T</i>’-WTe<sub>2</sub>, Published online: 04 October 2018; doi:10.1038/s41467-018-06635-xThe conductance from bulk bands in a topological insulator usually blurs effects arising from edge states. Here, Song et al. report a Coulomb gap opened by electron–electron interactions, which effectively suppress the bulk conductance and promote observation of topological edge states in the single-layer 1T’-WTe2.

Published in: "Nature Communications".

Photo-induced anomalous Hall effect in the type-II Weyl-semimetal WTe2 at room-temperature. (arXiv:1810.01510v1 [cond-mat.mtrl-sci])

2018-10-04T02:29:20+00:00October 4th, 2018|Categories: Publications|Tags: |

Using Hall photovoltage measurements, we demonstrate that an anomalous Hall-voltage can be induced in few layer WTe2 under circularly polarized light illumination. By applying a bias voltage along different crystal axes, we find that the photo-induced anomalous Hall conductivity coincides with a particular crystal axis. Our results are consistent with the underlying Berry-curvature exhibiting a dipolar distribution due to the breaking of crystal inversion symmetry. Using a time-resolved optoelectronic auto-correlation spectroscopy, we find that the decay time of the anomalous Hall voltage exceeds the electron-phonon scattering time by orders of magnitude but is consistent with the comparatively long spin-lifetime of carriers in the momentum-indirect electron and hole pockets in WTe2. Our observation suggests, that a helical modulation of an otherwise isotropic spin-current is the underlying mechanism of the anomalous Hall effect.

Published in: "arXiv Material Science".

Observation of the nonlinear Hall effect under time reversal symmetric conditions. (arXiv:1809.09279v1 [cond-mat.mes-hall])

2018-09-26T04:30:22+00:00September 26th, 2018|Categories: Publications|Tags: , |

The electrical Hall effect is the production of a transverse voltage under an out-of-plane magnetic field. Historically, studies of the Hall effect have led to major breakthroughs including the discoveries of Berry curvature and the topological Chern invariants. In magnets, the internal magnetization allows Hall conductivity in the absence of external magnetic field. This anomalous Hall effect (AHE) has become an important tool to study quantum magnets. In nonmagnetic materials without external magnetic fields, the electrical Hall effect is rarely explored because of the constraint by time-reversal symmetry. However, strictly speaking, only the Hall effect in the linear response regime, i.e., the Hall voltage linearly proportional to the external electric field, identically vanishes due to time-reversal symmetry. The Hall effect in the nonlinear response regime, on the other hand, may not be subject to such symmetry constraints. Here, we report the observation of the nonlinear Hall effect (NLHE) in the electrical transport of the nonmagnetic 2D quantum material, bilayer WTe2. Specifically, flowing an electrical current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of magnetic field. The NLHE exhibits unusual properties sharply distinct from the AHE in metals: The NLHE shows a quadratic I-V characteristic; It strongly dominates the nonlinear longitudinal response, leading to a Hall angle of about 90 degree. We further show that the NLHE directly measures the “dipole moment” of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new Hall effect and provide a powerful

Published : "arXiv Mesoscale and Nanoscale Physics".

Observation of the nonlinear anomalous Hall effect in 2D WTe2. (arXiv:1809.08744v1 [cond-mat.mes-hall])

2018-09-25T04:31:10+00:00September 25th, 2018|Categories: Publications|Tags: |

The Hall effect occurs only in systems with broken time-reversal symmetry, such as solids under an external magnetic field in the ordinary Hall effect and magnetic materials in the anomalous Hall effect (AHE). Here we show a new Hall effect in a nonmagnetic material under zero magnetic field, in which the Hall voltage depends quadratically on the longitudinal current. We observe the effect (referred to as nonlinear AHE) in two-dimensional Td-WTe2, a semimetal with broken inversion symmetry and only one mirror line in the crystal plane. Our angle-resolved electrical measurements reveal that the Hall voltage changes sign when the bias current reverses direction; it maximizes (vanishes) when the bias current is perpendicular (parallel) to the mirror line. The observed effect can be understood as an AHE induced by the bias current which generates an out-of-plane magnetization. The temperature dependence of the Hall conductivity further suggests that both intrinsic Berry curvature dipole and extrinsic spin-dependent scatterings contribute to the observed nonlinear AHE. Our results open the possibility of exploring the intrinsic Berry curvature effect in nonlinear electrical transport in solids .

Published : "arXiv Mesoscale and Nanoscale Physics".

Electrically Tunable Low Density Superconductivity in a Monolayer Topological Insulator. (arXiv:1809.04637v1 [cond-mat.mes-hall])

2018-09-14T02:29:22+00:00September 14th, 2018|Categories: Publications|Tags: |

The capability to switch electrically between superconducting and insulating states of matter represents a novel paradigm in the state-of-the-art engineering of correlated electronic systems. An exciting possibility is to turn on superconductivity in a topologically non-trivial insulator, which provides a route to search for non-Abelian topological states. However, existing demonstrations of superconductor-insulator switches have involved only topologically trivial systems, and even those are rare due to the stringent requirement to tune the carrier density over a wide range. Here we report reversible, in-situ electrostatic on off switching of superconductivity in a recently established quantum spin Hall insulator, namely monolayer tungsten ditelluride (WTe2). Fabricated into a van der Waals field effect transistor, the monolayer’s ground state can be continuously gate-tuned from the topological insulating to the superconducting state, with critical temperatures Tc up to ~ 1 Kelvin. The critical density for the onset of superconductivity is estimated to be ~ 5 x 10^12 cm^-2, among the lowest for two-dimensional (2D) superconductors. Our results establish monolayer WTe2 as a material platform for engineering novel superconducting nanodevices and topological phases of matter.

Published in: "arXiv Material Science".

Ferroelectric switching of a two-dimensional metal. (arXiv:1809.04575v1 [cond-mat.mtrl-sci])

2018-09-13T02:29:27+00:00September 13th, 2018|Categories: Publications|Tags: , |

A ferroelectric is a material with a polar structure whose polarity can be reversed by applying an electric field. In metals, the itinerant electrons tend to screen electrostatic forces between ions, helping to explain why polar metals are very rare. Screening also excludes external electric fields, apparently ruling out the possibility of polarity reversal and thus ferroelectric switching. In principle, however, a thin enough polar metal could be penetrated by an electric field sufficiently to be switched. Here we show that the layered topological semimetal WTe2 provides the first embodiment of this principle. Although monolayer WTe2 is centrosymmetric and thus nonpolar, the stacked bulk structure is polar. We find that two- or three-layer WTe2 exhibits a spontaneous out-of-plane electric polarization which 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. The critical temperature is above 350 K, and even when WTe2 is sandwiched in graphene it retains its switching capability at room temperature, demonstrating a robustness suitable for applications in combination with other two-dimensional materials.

Published in: "arXiv Material Science".

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