Superconductivity in type-II Weyl-semimetal WTe2 induced by a normal metal contact

Kononov, A.; Endres, Martin; Abulizi, Gulibusitan; Qu, Kejian; Yan, Jiaqiang; Mandrus, David; Watanabe, Kenji; Schönenberger, Christian

doi:10.1063/5.0021350

Cited by 33 publications

(23 citation statements)

References 51 publications

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“…The observation of superconductivity in our samples is an interesting phenomenon on its own and it requires a separate study [17]. Our WTe 2 crystals are not intrinsically superconducting.…”

Section: Superconductivity Induced In Wte 2 By Normal Leadsmentioning

confidence: 84%

One-Dimensional Edge Transport in Few-Layer WTe$_2$

Kononov,

Abulizi,

et al. 2019

Preprint

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WTe 2 is a layered transitional metal dichalcogenide (TMD) with a number of intriguing topological properties. The bulk crystal is a Weyl semimetal with Fermi arc surface states and the monolayer is a two-dimensional (2D) topological insulator. Recently, WTe 2 has also been predicted to be a higher-order topological insulator (HOTI) with hinge states along the edges. The gapless nature of WTe 2 complicates the observation of one-dimensional (1D) topological states in transport due to their small contribution relative to the bulk. Here, the Josephson effect can help to detect the edge transport, since the evolution of the critical current in magnetic field is sensitive to the spatial current distribution. Here, we employ superconducting contacts in WTe 2 that emerge when Pd is placed in contact with the TMD to define Josephson junctions. Using the Josephson effect, we demonstrate the presence of 1D current carrying states residing on the edges and steps of few-layer WTe 2 crystals. The width of the 1D current-carrying states is deduced to be below 80 nm. A supercurrent I c is measured over distances up to 3 µm and persisting in magnetic fields up to B = 2 T. This observation is in good agreement with the recent prediction of HOTI states in WTe 2 . Moreover, the observed dependencies of I c (B) on magnetic field demonstrate a particular symmetry with the direction of the current and the magnetic field, which matches the prediction for topological states in systems with broken inversion symmetry. Our observation adds another effect to a plethora of intriguing properties of WTe 2 and potentially provides a new platform for obtaining Majorana zero modes.

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Section: Superconductivity Induced In Wte 2 By Normal Leadsmentioning

confidence: 84%

One-Dimensional Edge Transport in Few-Layer WTe$_2$

Kononov,

Abulizi,

et al. 2019

Preprint

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“…The van-der-Waals (vdW) material WTe 2 is predicted to be a higher-order TI [11][12][13][14][15], hosting topological edge states at its crystal hinges. It was recently shown that thin crystals of the material placed on top of palladium (Pd) bottom contacts turn superconducting [16], with a pronounced flow of super-current along the edges of a Josephson junction (JJ) formed out of this material system [17].…”

Section: Introductionmentioning

confidence: 99%

Transparent Josephson Junctions in Higher-Order Topological Insulator WTe2 via Pd Diffusion

Endres,

Kononov,

Stiefel

et al. 2022

Preprint

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Highly transparent superconducting contacts to a topological insulator (TI) remain a persistent challenge on the route to engineer topological superconductivity. Recently, the higher-order TI WTe2 was shown to turn superconducting when placed on palladium (Pd) bottom contacts, demonstrating a promising material system in perusing this goal. Here, we report the diffusion of Pd into WTe2 and the formation of superconducting PdTex as the origin of observed superconductivity. We find an atomically sharp interface between the diffusion layer and its host crystal, forming state-of-the-art superconducting contacts to a TI. The diffusion is discovered to be non-uniform along the width of the WTe2 crystal, with a greater extend along the edges compared to the bulk. The potential of this contacting method is highlighted in transport measurements on Josephson junctions by employing external superconducting leads.

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“…Another characteristic feature of WTe 2 is the extreme positive transverse magnetoresistance MR ⊥ , which can reach values as high as 10 5 % for magnetic fields ∼9 T applied parallel to the c−axis of bulk or thin flakes of WTe 2 in the Fermi liquid phase at T ∼ 100 mK [40][41][42]. In addition, evidence of topologically protected conducting edge states [43] and flat-band superconductivity in close proximity to Pd [44] and Nb [45] was shown in bulk and few layers WTe 2 flakes, while quantum spin Hall states are found in mechanically exfoliated monolayer WTe 2 [46]. Most of the reported literature on T d -WTe 2 concerns bulk crystals or mechanically exfoliated flakes.…”

Section: Introductionmentioning

confidence: 99%

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

Adhikari

Faina

et al. 2021

Nanomaterials

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Layered van der Waals semimetallic Td-WTe2, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of Td-WTe2 are studied via atomic force microscopy, Raman spectroscopy, low-T/high-μ0H magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse MR⊥ and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse MR⊥∼1200 % and an average carrier mobility of 5000 cm2V−1s−1 at T=5K for an applied perpendicular field μ0H⊥=7T are established. The system follows a Fermi liquid model for T≤50K and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe2 flakes is found to persist up to T=120K, a temperature at least four times higher than the ones reported to date.

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Superconductivity in type-II Weyl-semimetal WTe2 induced by a normal metal contact

Cited by 33 publications

References 51 publications

One-Dimensional Edge Transport in Few-Layer WTe$_2$

One-Dimensional Edge Transport in Few-Layer WTe$_2$

Transparent Josephson Junctions in Higher-Order Topological Insulator WTe2 via Pd Diffusion

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

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