Superconductivity in the niobium-selenium system

Revolinsky, E.; Spiering, G.A.; Beerntsen, D. J.

doi:10.1016/0022-3697(65)90190-3

Cited by 135 publications

(56 citation statements)

References 7 publications

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“…In 1T-TaS 2 a mere 50 ppm of isoelectronic Nb impurities were observed to destroy the long range phase coherence of the commensurate CDW and completely suppress the associated metal-insulator (MI) transition [4]. On intercalation, the T c in Ta compounds increases from < 1 K upto 5 K while it is lowered for Nb [5]- [9]. In self-intercalated 2H-Nb 1.05 Se 2 the T c was suppressed below 2.2 K [5], while 2H-NbSe 2 (EDA) 1/4 showed no superconductivity but a resistance minimum at ∼ 25 K [7].…”

Section: Introductionmentioning

confidence: 99%

“…On intercalation, the T c in Ta compounds increases from < 1 K upto 5 K while it is lowered for Nb [5]- [9]. In self-intercalated 2H-Nb 1.05 Se 2 the T c was suppressed below 2.2 K [5], while 2H-NbSe 2 (EDA) 1/4 showed no superconductivity but a resistance minimum at ∼ 25 K [7]. Post-transition metal intercalated 2H-NbS 2 also did not show superconductivity [8].…”

Section: Introductionmentioning

confidence: 99%

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Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂

Niazi¹,

Rastogi²

2001

J. Phys.: Condens. Matter

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We report the structural and electron transport properties of 3R-Nb1+xS2 (x ≥ .07) and 3R-GaxNbS2 (.1 ≤ x ≤ .33) prepared as polycrystalline pellets as well as single crystals grown by vapour transport. We observe a resistance minimum in these compounds between 20-60 K, with the Tmin proportional to x. The resistance scales as ρ/ρmin(T /Tmin) between .2 < T /Tmin < 2 for different phases with x ≤ .25 whose resistivity differs by an order of magnitude. Powder X-ray diffraction (XRD) also shows progressively increasing intensity of superlattice lines with cation concentration. The thermopower changes sign around the resistance minimum. The explanation of the resistance minimum and the simultaneous rapid suppression of superconductivity is sought in e-e scattering effects in the presence of cation disorder in these narrow band anisotropic materials.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂

Niazi¹,

Rastogi²

2001

J. Phys.: Condens. Matter

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“…Layered transition metal dichalcogenide (TMD) is one of the most important material groups that shows plenty physical phenomena such as charge density waves [13,14], superconductivity [15,16], metal-insulator-transition [17], unsaturate magneto-resistance [18], etc. One of the TMDs, PdTe 2 is an intermetallic compound and is known to become a superconductor below T c =1.7 K [19], which is comparable to other TMD superconductors.…”

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confidence: 99%

Experimental Realization of Type-II Dirac Fermions in a PdTe2 Superconductor

Noh¹,

Jeong²,

Cho³

et al. 2017

Phys. Rev. Lett.

284

212

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A Dirac fermion in a topological Dirac semimetal is a quadruple-degenerate quasi-particle state with a relativistic linear dispersion. Breaking either time-reversal or inversion symmetry turns this system into a Weyl semimetal that hosts double-degenerate Weyl fermion states with opposite chiralities. These two kinds of quasi-particles, although described by a relativistic Dirac equation, do not necessarily obey Lorentz invariance, allowing the existence of so-called type-II fermions. Recent theoretical discovery of type-II Weyl fermions evokes the prediction of type-II Dirac fermions in PtSe 2 -type transition metal dichalcogenides, expecting an experimental confirmation. Here, we report an experimental realization of type-II Dirac fermions in PdTe 2 by angle-resolved photoemission spectroscopy combined with ab-initio band calculations. Our experimental finding makes the first example that has both superconductivity and type-II Dirac fermions, which turns the topological material research into a new phase.

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“…2H-NbSe 2 is a prototypical CDW compound. It was originally investigated over four decades ago as one of the first layered materials, in which superconductivity was observed (T SC (2H-NbSe 2 ) = 7.2 K) [3]. Only afterwards it was realized that 2H-NbSe 2 undergoes a CDW phase transition already at T CDW = 33 K [4], however, the exact distortion pattern at T < T CDW is still a subject of current research [5].…”

Section: Introductionmentioning

confidence: 99%

Optical phonons and the soft mode in 2H-NbSe2

et al. 2013

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We present an investigation of the lattice dynamics of the charge-density-wave compound 2H-NbSe 2 . We analyze the precise nature of the wave vector dependent electron-phonon coupling (EPC) and derive the bare dispersion of the charge-density-wave (CDW) soft phonon mode using inelastic x-ray scattering combined with ab-initio calculations. Experimentally, phonon modes along the Γ -M line, i.e. q = (h, 0, 0) with 0 ≤ h ≤ 0.5, with the same longitudinal symmetry (Σ 1 ) as the CDW soft mode were investigated up to 32 meV. In agreement with our calculations we observe significant EPC in the optic modes at h ≤ 0.2. We analyze the EPC in the optic as well as acoustic modes and show that the q dependences stem from scattering processes between two bands at the Fermi surface both having Nb 4d character. Finally, we demonstrate that the soft mode dispersion at T = 33 K (= T CDW ) can be well described on the basis of a strongly q dependent EPC matrix element and an acoustic-like bare phonon dispersion in agreement with observations near room temperature.

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Superconductivity in the niobium-selenium system

Cited by 135 publications

References 7 publications

Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂

Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂

Experimental Realization of Type-II Dirac Fermions in a PdTe2 Superconductor

Optical phonons and the soft mode in 2H-NbSe2

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Superconductivity in the niobium-selenium system

Cited by 135 publications

References 7 publications

Low-temperature resistance minimum in non-superconducting 3R-Nb1+xS2and 3R-GaxNbS2

Low-temperature resistance minimum in non-superconducting 3R-Nb1+xS2and 3R-GaxNbS2

Experimental Realization of Type-II Dirac Fermions in a PdTe2 Superconductor

Optical phonons and the soft mode in 2H-NbSe2

Contact Info

Product

Resources

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Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂

Low-temperature resistance minimum in non-superconducting 3R-Nb_1+xS₂and 3R-Ga_xNbS₂