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Moncton, D. E.; Axe, J. D.; DiSalvo, F. J.

doi:10.1103/physrevb.16.801

Cited by 520 publications

(260 citation statements)

References 19 publications

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“…[1][2][3][4][5][6][7][8][9][10] For example, artificial van der Waals heterostructures with high on/off current ratio in TMDs are promising as an active channel for next-generation devices. [2] Topological field-effect transitions based on quantum spin Hall (QSH) insulators are novel type of device.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity enhancement in the S-doped Weyl semimetal candidate MoTe2

Chen

Luo

Xiao

et al. 2016

Applied Physics Letters

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Two-dimensional (2D) transition-metal dichalcogenide (TMDs) MoTe 2 has attracted much attention due to its predicted Weyl semimetal (WSM) state and a quantum spin Hall insulator in bulk and monolayer form, respectively. We find that the superconductivity in MoTe 2 single crystal can be much enhanced by the partial substitution of the Te ions by the S ones. The maximum of the superconducting temperature T C of MoTe 1.8 S 0.2 single crystal is about 1.3 K. Compared with the parent MoTe 2 single crystal (T C =0.1 K), nearly 13-fold in T C is improved in MoTe 1.8 S 0.2 one.The superconductivity has been investigated by the resistivity and magnetization measurements.MoTe 2-x S x single crystals belong to weak coupling superconductors and the improvement of the superconductivity may be related to the enhanced electron-phonon coupling induced by the S-ion substitution. A dome-shape superconducting phase diagram is obtained in the S-doped MoTe 2 single crystals. MoTe 2-x S x materials may provide a new platform for our understanding of superconductivity phenomena and topological physics in TMDs. II Experimental details 3MoTe 2 and MoTe 2-x S x (0≤x≤1) single crystals were grown by the chemical vapor transport method using polycrystalline MoTe 2 and MoTe 2-x S x as raw materials and I 2 as a transport agent.Firstly, we made the polycrystalline MoTe 2 and MoTe 2-x S x (0≤x≤1). Mo (Alfa Aesar, 99.9 %) and Te or S(Alfa Aesar, 99.9 %) powders with a stoichiometric ratio were ground, pressed into pellets, and put in an evacuated quartz tube. All were done in an Ar-filled glove box. The sealed quartz tube was heated to 800 o C for 20 hours and kept for 7 days, then quenched to ice water. The polycrystalline MoTe 2 or MoTe 2-x S x and the agent I 2 were mixed and sealed into another evacuated quartz tubes. The sealed quartz tubes were put in a two-zone tube furnace. The crystal growth recipe is followed the reported paper.[12] The hot side is about 1000 o C and the cold side is 900 o C, and dwelled for 7 days. In order to improve the quality of single crystals, we quenched the quartz tubes into ice-water as soon as possible before the growth sequence ending. Plate-like shape single crystals with shinning surfaces were obtained. The size of the crystal was about 4*4*0.5 mm 3 . The single crystals were air-stable and can be easily exfoliated. Powder X-ray diffraction (XRD) patterns were taken with Cu K α1 radiation (λ=0.15406 nm) using a PANalytical X'pert diffractometer at room temperature. The element analysis of the single crystals was performed using a commercial energy dispersive spectroscopy (EDS) microprobe. The element compositions of the single crystals used in the text are the ones obtained from EDS measurements.The magnetic properties were carried out by the magnetic property measurement system with a 3 He cryostat (MPMS-XL7). The electrical transport measurements were performed in a 4 He cryostat from 300 K to 2 K, and in a 3 He cryostat down to 0.35 K by a four-probe method to eliminate the contact resistan...

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Section: Introductionmentioning

confidence: 99%

Superconductivity enhancement in the S-doped Weyl semimetal candidate MoTe2

Chen

Luo

Xiao

et al. 2016

Applied Physics Letters

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“…Anisotropies or modulations of the superconducting properties (in real and/or reciprocal space) often appear as a consequence of competing orders within the same system [1,2]. In the compound 2H-NbSe 2 , superconductivity appears within a CDW state (T CDW =33K and T c =7.2 K) [3]. Low lying excitations measured deep in the superconducting state long time ago by specific heat [4,5] have been explained by recent experiments and theoretical calculations with a multiband superconductivity and a peculiar anisotropy of the superconducting gap [6,7].…”

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confidence: 99%

Superconducting Density of States and Vortex Cores of 2H-NbS2

et al. 2008

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Scanning tunneling microscopy and spectroscopy (STM/S) measurements in the superconducting dichalcogenide 2H-NbS2 show a peculiar superconducting density of states with two well defined features at 0.97 meV and 0.53 meV, located respectively above and below the value for the superconducting gap expected from single band s-wave BCS model (∆=1.76kBTc=0.9 meV). Both features have a continuous temperature evolution and disappear at Tc = 5.7 K. Moreover, we observe the hexagonal vortex lattice with radially symmetric vortices and a well developed localized state at the vortex cores. The sixfold star shape characteristic of the vortex lattice of the compound 2H-NbSe2 is, together with the charge density wave order (CDW), absent in 2H-NbS2.PACS numbers: 71.45. Lr, 74.25.Jb,74.50.+r,74.70.Ad The study of the coexistence of superconductivity with competing physical phenomena such as magnetic or charge order has historically produced great interest on the scientific community. Anisotropies or modulations of the superconducting properties (in real and/or reciprocal space) often appear as a consequence of competing orders within the same system [1,2]. In the compound 2H-NbSe 2 , superconductivity appears within a CDW state (T CDW =33K and T c =7.2 K) [3]. Low lying excitations measured deep in the superconducting state long time ago by specific heat [4,5] have been explained by recent experiments and theoretical calculations with a multiband superconductivity and a peculiar anisotropy of the superconducting gap [6,7]. Recent angular resolved photoemission spectroscopy measurements demonstrate that the superconducting gap has, close to T c (at 5.7 K), largest values at k-space positions connected with CDW wavevectors [8,9]. Hess et al. [10,11,12] found that the local superconducting density of states (LDOS) at the center of the vortex core shows a high peak close to the Fermi level highlighting the lowest quasiparticle state bound within the vortex core well [13]. Around the vortex core, the LDOS is far from respecting in-plane symmetry and intriguing vortex lattice images with patterns showing strong in-plane LDOS modulations are obtained [10,11,12]. 2H-NbSe 2 belongs to the transition-metal dichalcogenides (2H-MX 2 with M = Ta, Nb and X = Se, S), a family of systems which is unique to study the interplay between CDW order and superconductivity. The 2H-MX 2 compounds share a double layered structure made of two hexagonal X sheets with an intercalated M sheet (X-M-X), connected through very weak van der Waals bonds [14]. This produces highly anisotropic, quasi two dimensional electronic properties. The features of the Fermi Surface (FS) expected to be common in all systems of the series are two concentric cylindrical FS sheets centered on both Γ and K points, derived from the transition-metal d bands [15,16,17,18]. When going over the series from 2H-TaSe 2 and 2H-TaS 2 to 2H-NbSe 2 and 2H-NbS 2 , the ratio of the intralayer lattice constant with the interlayer distance a/c increases, as well as T c , whereas T CDW decreas...

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“…The detailed neutron diffraction experiments of Moncton et al [21] have determined that the ionic displacements have 1 symmetry, which corresponds to longitudinal motion of the Ta atoms in the basal plane with amplitude given by experiment. However, the fitting procedure to the measured geometric structure factors was insensitive to the overall phase ' of the distortions.…”

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confidence: 99%

Coexistence of Gapless Excitations and Commensurate Charge-Density Wave in the2HTransition Metal Dichalcogenides

et al. 2006

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An unexpected feature common to 2H-transition metal dichalcogenides (2H-TMDs) is revealed with first-principles Wannier functions analysis of the electronic structure of the prototype 2H-TaSe2: The low-energy Ta "5d z 2 " bands governing the physics of charge-density wave (CDW) is dominated by hopping between next-nearest neighbors. With this motivation we develop a minimal effective model for the CDW formation, in which the unusual form of the hopping leads to an approximate decoupling of the three sublattices. In the CDW phase one sublattice remains undistorted, leaving the bands associated with it ungapped everywhere in the Fermi surface, resolving the long-standing puzzle of coexistence of gapless excitations and commensurate CDW in the 2H-TMDs.

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Neutron scattering study of the charge-density wave transitions in2H−TaSe2and2H−

Cited by 520 publications

References 19 publications

Superconductivity enhancement in the S-doped Weyl semimetal candidate MoTe2

Superconductivity enhancement in the S-doped Weyl semimetal candidate MoTe2

Superconducting Density of States and Vortex Cores of 2H-NbS2

Coexistence of Gapless Excitations and Commensurate Charge-Density Wave in the2HTransition Metal Dichalcogenides

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