Electronic structure and weak electron-phonon coupling in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">TaB</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Rösner, H.; Pickett, Warren E.; Drechsler, S.‐L.; Handstein, A.; Behr, G.; Fuchs, G.; Nenkov, K.; Müller, K.‐H.; Eschrig, H.

doi:10.1103/physrevb.64.144516

Cited by 75 publications

(61 citation statements)

References 20 publications

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“…On the other hand, Rosner et al showed 10 that SC in TaB 2 was absent down to 1.5 K, and according to 7,8 the SC transition for NbB 2 is not observed to T ∼ 2K, in conformity with earlier data 6 . The weak electron-phonon coupling estimated to be inconsistent with superconductivity in ZrB 2 14 leads to T c ∼ 0.1 K in TaB 2 13 and is responsible only for T c ∼ 3K in NbB 2 12 .…”

supporting

confidence: 68%

Effect of metal vacancies on the band structure of Nb, Zr, and Y diborides

2003

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Energy band structures of metal-deficient hexagonal diborides M0.75B2 (M = Nb, Zr and Y) were calculated using the full-potential LMTO method. The metal vacancies change the density of states near the Fermi level and this effect is quite different for III-V group transition metal diborides. Contradictory data on superconductivity in diborides may be supposed to be connected with nonstoichiometry of samples. Vacancy formation energies are estimated and analyzed. * E-mail: shein@ihim.uran.ru A recent discovery of superconductivity (SC) in MgB 2 (T c ≈ 39 K) 1 and creation of promising materials based thereon (see reviews [2−5] ) have attracted a great deal of interest in hexagonal transition metal (M) diborides isostructural with MgB 2 [2−5] . Earlier investigations observed no superconductivity in d-metal diborides (Ti, Zr, Hf, V, Ta, Cr, Mo, Nb) with temperatures above 0.6 K 6 . Experimental and theoretical investigations [7−17] showed that the supercoductivity with T c ≈ 40K is unlikely in all undoped diborides except MgB 2 , where the high value of T c is explained by strong electron-phonon coupling and high phonon frequencies and is closely connected with the existence of hole doped boron σ bands.Recently, rather high T c have been reported for ZrB 2 (5.5K) 7 , TaB 2 (9.5K) 8 and NbB2 (5.2K) 9 . On the other hand, Rosner et al showed 10 that SC in TaB 2 was absent down to 1.5 K, and according to 7,8 the SC transition for NbB 2 is not observed to T ∼ 2K, in conformity with earlier data 6 . The weak electron-phonon coupling estimated to be inconsistent with superconductivity in ZrB 2 14 leads to T c ∼ 0.1 K in TaB 2 13 and is responsible only for T c ∼ 3K in NbB 2 12 . So, both experimental and theoretical studies performed to characterize and understand superconductivity in MB 2 yielded contradictory results. It is important also to note that in all the studies [7−17] the composition of transition metal diborides was considered to be strictly stoichiometric (B/M = 2). As is known, lattice vacancies are typical defects, and their presence may change considerably the properties of non-stoichiometric materials in the homogeneity region. For instance, one of the most familiar classes of non-stoichiometric compounds with exclusively wide homogeneity regions (to 30 ∼ 55 at %) includes cubic (B1) III-V group transition metal carbides, nitrides and oxides extensively investigated in numerous works, see 18 . As distinct from the above B1 -carbides, nitrides and oxides, III-V group metal diborides have very narrow homogeneity regions under equilibrium conditions 19 . Therefore the role of non-stoichiometry is usually ignored when their properties are examined. No theoretical studies describing the effect of lattice vacancies on the electronic structure of metal diborides are familiar to us either. Quite recently, Yamamoto et al20 have carried out a highpressure synthesis of a series of metal-deficient samples of the AlB 2 -type Nb 1−x B 2 , Ta 1−x B 2 (0 < x < 0.48) and Mo 2 B 5 -type borides with the compositions ...

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confidence: 68%

Effect of metal vacancies on the band structure of Nb, Zr, and Y diborides

2003

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“…[3][4][5][6][7] In addition, AgB 2 and AuB 2 were predicted to have T c higher than 50 K from the theoretical estimates, 8,9 but recently much lower T c $ 7 K than theoretically predicted was found experimentally in AgB 2 thin films. 10 It should also be noted that, despite a favorable prediction of their high T c , [11][12][13][14] it is difficult to synthesize these materials with an AlB 2 structure.…”

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confidence: 85%

Critical current density and flux pinning in Zr0.96V0.04B2 superconductor with AlB2 structure

Jung

Vanacken

Moshchalkov

et al. 2013

Journal of Applied Physics

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We have investigated the critical current density (Jc) and the flux pinning behavior in Zr0.96V0.04B2 superconductor with an AlB2 structure. V substitutions in Zr sites of non-superconducting ZrB2 system lead to superconductivity, and the 4% V-substituted Zr0.96V0.04B2 compounds show the highest superconducting transition temperature (Tc) of ∼8.7 K. The magnetic hysteresis (M−H) loops for the Zr0.96V0.04B2 demonstrate type-II superconducting behavior in a broad temperature range, and the Jc is estimated from the M−H loops using the Bean model. The analysis of the double-logarithmic Jc(H) plots indicates the dominance of collective pinning in Zr0.96V0.04B2, and that Jc(H) and magnetic field dependences of the flux pinning force density (Fp) are well fitted by the double exponential model which takes into account the existence of two superconducting gaps.

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“…23 The mode at 1180 cm -1 seen in the reflectivity spectrum reported on their samples is also seen in our samples, however, it is noteworthy that our synthesis procedure is entirely different from that adopted earlier. (15) 1323 (19) 1326 (17) 1330(12) 1330 (13) 1336 (12) 1338 (13) 1340 (12) Figure. …”

Section: Discussionmentioning

confidence: 99%

Synthesis and search for superconductivity in LiBC

Bharathi

Balaselvi

Premila

et al. 2002

Solid State Communications

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Following the recent theoretical prediction of superconductivity in hole doped LiBC by Rosner et al [1], we have attempted to synthesise Li deficient Li x BC ( x = 1, 0.8, 0.6 and 0.4) and look for superconductivity in this system. Our synthesis procedure, following the recipe for MgB 2 , involves reaction of elemental components in a Ta crucible at 900o C under 50 bar of argon pressure. X-ray diffraction measurements indicate the formation of P6 3 /mmc structure up to x=0.6. However, no diamagnetic signal or zero resistance, corresponding to the superconducting transition, was observed in the temperature range of 300 to 4 K. This is possibly related to the presence of disorder in the B-C stacking; evidence for which is suggested from a study of the vibrational modes of Li x BC through infrared spectroscopy.

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Electronic structure and weak electron-phonon coupling inTaB2

Cited by 75 publications

References 20 publications

Effect of metal vacancies on the band structure of Nb, Zr, and Y diborides

Effect of metal vacancies on the band structure of Nb, Zr, and Y diborides

Critical current density and flux pinning in Zr0.96V0.04B2 superconductor with AlB2 structure

Synthesis and search for superconductivity in LiBC

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