Signatures of the topological s
            +− superconducting order parameter in the type-II Weyl semimetal T
            d-MoTe2

Guguchia, Zurab; Rohr, Fabian von; Shermadini, Z.; Lee, A. T.; Banerjee, Soham; Wieteska, Andrew; Marianetti, Chris A.; Frandsen, Benjamin A.; Luetkens, H.; Gong, Zizhou; Cheung, Sky C.; Baines, C.; Shengelaya, А.; Taniashvili, Grigol; Pasupathy, Abhay; Morenzoni, E.; Billinge, Simon J. L.; Amato, A.; Cava, R. J.; Khasanov, R.; Uemura, Yohei

doi:10.1038/s41467-017-01066-6

Cited by 122 publications

(157 citation statements)

References 71 publications

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“…A high-pressure muon-spin rotation study of superconductivity in MoTe 2 suggested that a topologically non-trivial s +− state likely exists in MoTe 2 at pressures up to 1.9 GPa. 18 Key components to a TSC state are the crystal structure and band topology under pressure. Existing reports stop short of exploring the symmetry in the superconducting phase under pressure and no calculations exist on the electronic band structure.…”

Section: Introductionmentioning

confidence: 99%

Electronic band tuning under pressure in MoTe2 topological semimetal

et al. 2019

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Topological superconductors (TSC) can host exotic quasiparticles such as Majorana fermions, poised as the fundamental qubits for quantum computers. TSC's are predicted to form a superconducting gap in the bulk, and gapless surface/edges states which can lead to the emergence of Majorana zero energy modes. A candidate TSC is the layered dichalcogenide MoTe 2 , a type-II Weyl (semi) metal in the non-centrosymmetric orthorhombic (T d) phase. It becomes superconducting upon cooling below 0.25 K, while under pressure, superconductivity extends well beyond the structural boundary between the orthorhombic and monoclinic (1T′) phases. Here, we show that under pressure, coupled with the electronic band transition across the T d to 1T′ phase boundary, evidence for a new phase, we call T d * is observed and appears as the volume fraction of the T d phase decreases in the coexistence region. T d * is most likely centrosymmetric. In the region of space where T d * appears, Weyl nodes are destroyed. T d * disappears upon entering the monoclinic phase as a function of temperature or on approaching the suppression of the orthorhombic phase under pressure above 1 GPa. Our calculations in the orthorhombic phase under pressure show significant band tilting around the Weyl nodes that most likely changes the spin-orbital texture of the electron and hole pockets near the Fermi surface under pressure that may be linked to the observed suppression of magnetoresistance with pressure.

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Section: Introductionmentioning

confidence: 99%

Electronic band tuning under pressure in MoTe2 topological semimetal

et al. 2019

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“…MoTe 2 is an interesting member of the family of the transition metal dichalcogenides because of the multiple structural phases in which the compound can exist. 25,26 At 250 K, MoTe 2 shows a structural phase transition where a high temperature inversion symmetric monoclinic phase finds a new ground state with noncentrosymmetric orthorhombic structure (space group: P mn21, T d Phase). 27 The Orthorhombic T d phase is a Weyl semimetal 28,29 which is also known to show superconductivity below a very low critical temperature (T c ) of 0.1 K. 30 By introducing strain in the crystals of MoTe 2 through large external hydrostatic pressure, it has also been possible to enhance the T c of MoTe 2 significantly.…”

mentioning

confidence: 99%

Generation of strain-induced pseudo-magnetic field in a doped type-II Weyl semimetal

Kamboj

Rana²,

Sirohi³

et al. 2019

Phys. Rev. B

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In Weyl semimetals, there is an intriguing possibility of realizing a pseudo-magnetic field in presence of small strain due to certain special cases of static deformations. This pseudo-magnetic field can be large enough to form quantized Landau levels and thus become observable in Weyl semimetals. In this paper we experimentally show the emergence of a pseudo-magnetic field (∼ 3 Tesla) by Scanning Tunneling Spectroscopy (STS) on the doped Weyl semimetal Re-MoTe2, where distnict Landau level oscillations in the tunneling conductance are clearly resolved. The crystal lattice is intrinsically strained where large area STM imaging of the surface reveals differently strained domains where atomic scale deformations exist forming topographic ripples with varying periodicity in the real space. The effect of pseudo-magnetic field is clearly resolved in areas under maximum strain.

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“…The data of Cu 0.09 Bi 2 Se 3 were extracted from our magnetization measurement, and other data points of Cu x Bi 2 Se 3 were obtained from magnetization and μSR measurements in previous reports [53,55]. [143], Nb 0.5 Os 0.5 [114], Re 6 Zr [144], Mo 3 P [113], and BeAu [145], thin films of transition-metal nitrides NbN [14,91], heavy fermions superconductors UPt 2 , UBe 13 and Ce 1−x Yb x CoIn 5 [146][147][148], and conventional metal superconductors [82,119].…”

Section: Discussionmentioning

confidence: 98%

Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport

Fang

You

2020

New J. Phys.

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Although the Cu doped Bi 2 Se 3 topological insulator was discovered and intensively studied for almost a decade, its electrical and magnetic properties in normal state, and the mechanism of 'high-T c ' superconductivity regarding the relatively low-carrier density are still not addressed yet. In this work, we report a systematic investigation of magnetic susceptibility, critical fields, and electrical transport on the nominal Cu 0.20 Bi 2 Se 3 single crystals with T onset c = 4.18 K, the highest so far. The composition analysis yields the Cu stoichiometry of x = 0.09(1). The magnetic susceptibility shows considerable anisotropy and an obvious kink at around 96 K was observed in the magnetic susceptibility for H c, which indicates a charge density anomaly. The electrical transport measurements indicate the two-dimensional (2D) Fermi liquid behavior at low temperatures with a high Kadowaki-Woods ratio, A/γ 2 = 30.3a 0 . The lower critical field at 0 K limit was extracted to be 6.0 Oe for H ab. In the clean limit, the ratio of energy gap to T c was determined to be Δ 0 /k B T c = 2.029 ± 0.124 exceeding the standard BCS value 1.764, suggesting Cu 0.09 Bi 2 Se 3 is a strong-coupling superconductor. The in-plane penetration depth at 0 K was calculated to be 1541.57 nm, resulting in an unprecedented high ratio of T c /λ −2 (0) ∼ = 9.86. Moreover, the ratio of T c to Fermi temperature is estimated to be T c /T 2D F = 0.034. Both ratios fall into the region of unconventional superconductivity according to Uemura's regime, supporting the unconventional superconducting mechanism in Cu x Bi 2 Se 3 . Finally, the enhanced T c value higher than 4 K is proposed to arise from the increased density of states at Fermi energy and strong electron-phonon interaction induced by the charge density instability. 1 K, such as SrTiO 3 (T c ∼ 0.05-0.29 K, n e = 0.65 to 42.4 × 10 20 cm −3 ) [3,4], GeTe (T c ∼ 0.07-0.3 K, n e = 8.6 to 15.2 × 10 20 cm −3 ) [5], and SnTe (T c ∼ 0.034-0.214 K, n p = 7.5 to 20.0 × 10 20 cm −3 ) [6]. To compare with these systems, the T c value of Cu x Bi 2 Se 3 is relatively 'high' given it is a highly doped narrow semiconductor with lower carrier density. However, the mechanism of such anomalous enhanced T c phenomenon remains unclear despite nearly a decade of extensive research. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft New J. Phys. 22 (2020) 053026 Y Fang et alThe emergence and enhancement of superconductivity may occur in various cases by tailoring the ground states of quantum materials. For example, suppression of charge density wave (CDW) by chemical doping or pressure is observed in many systems [7-10], including low dimensional layered Cu x TiSe 2 and three dimensional (3D) alloys Lu(Pt 1−x Pd x ) 2 In and (Sr, Ca) 3 Ir 4 Sn 13 , 3D oxides Ba 1−x K x BiO 3 . Similarly, the magnetic ordering or spin density wave (SDW) have also been suppressed in strongly correlated heavy fermions materials, high-T c cuprates and i...

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Signatures of the topological s +− superconducting order parameter in the type-II Weyl semimetal T d-MoTe2

Cited by 122 publications

References 71 publications

Electronic band tuning under pressure in MoTe2 topological semimetal

Electronic band tuning under pressure in MoTe2 topological semimetal

Generation of strain-induced pseudo-magnetic field in a doped type-II Weyl semimetal

Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport

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Signatures of the topological s +− superconducting order parameter in the type-II Weyl semimetal T d-MoTe2

Cited by 122 publications

References 71 publications

Electronic band tuning under pressure in MoTe2 topological semimetal

Electronic band tuning under pressure in MoTe2 topological semimetal

Generation of strain-induced pseudo-magnetic field in a doped type-II Weyl semimetal

Unconventional superconductivity in CuxBi2Se3 from magnetic susceptibility and electrical transport

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Product

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Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport