Structural and superconducting properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MgB</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

Ahn, J. S.; Kim, Young‐Jin; Kim, M.-S.; Lee, S.-I.; Choi, E. J.

doi:10.1103/physrevb.65.172503

Cited by 27 publications

(9 citation statements)

References 18 publications

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“…By the substitution of Li, which corresponds to hole doping 8 T c remains constant. Whereas by Be substitution, which also results in hole doping, 9 T c shows a precipitous decrease, 10 which is understood in terms a decrease in the electron phonon coupling strength. 11 It therefore appears that the route to increase T c is to increase the electron-phonon coupling strength with the hole concentration remaining fixed atleast at the MgB 2 value.…”

Section: Introductionmentioning

confidence: 96%

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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Section: Introductionmentioning

confidence: 96%

Synthesis and search for superconductivity in LiBC

Bharathi

Balaselvi

Premila

et al. 2002

Solid State Communications

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“…Indeed, based on band structure calculations and the Eliashberg theory, it was argued that the observed decrease of T c of Al and C doped MgB 2 samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C [23,24]. Finally we note that NbB 2+x [14,25,26], Nb 1−x B 2 [27], MgB 2−x Be x [13] are additional potential candidates, as well as overdoped cuprates [28,29,30]. In particular, evidence for 1/λ (0)…”

Section: Andmentioning

confidence: 61%

“…and NbB 2+x , where superconductivity disappears at some critical value x = x c [11,12,13,14], whereupon a quantum superconductor to metal (QSM) transition is expected to occur. To illustrate this behavior we depicted in Fig.…”

Section: Andmentioning

confidence: 99%

Quantum Superconductor-Metal Transition in Al, C doped MgB2 and Overdoped Cuprates?

Schneider

2007

High Tc Superconductors and Related Transition Metal Oxides

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We consider the realistic case of a superconductor with a nonzero density of elastic scatterers, so that the normal state conductivity is finite. The quantum superconductor-metal (QSM) transition can then be tuned by varying either the attractive electron-electron interaction, the quenched disorder, or the applied magnetic field. We explore the consistency of the associated scaling relations,valid for all dimensions D > 2, with experimental data, in Al, C doped MgB2 and overdoped cuprates. PACS numbers:Understanding the phenomenon of superconductivity, now observed in quite disparate systems, such as simple elements, fullerenes, molecular metals, cuprates, borides, etc., involves searching for universal relations between superconducting properties across different materials, which might provide hints towards a unique classification. In spite of the great impact of the BCS theory [1], the discovery of superconductivity in the cuprates in 1986 [2] made it clear that the BCS relations between the critical amplitudes of the gap (∆ 0 ), the correlation length (ξ 0 ), the magnetic penetration depth (λ 0 ), the upper critical field (H c20 ) and the transition temperature T c , namely [3]Here, λ (T ) = λ 0 t 1/2 , ∆ (T ) = ∆ 0 t 1/2 ≃ 1.76∆ (0) t 1/2 , ξ (T ) = ξ 0 t −1/2 , and H c2 = H c20 t, close to the superconductor metal transition, with t = 1 − T /T c and 2∆ (0) / (k B T c ) ≃ 3.52. Furthermore, there are empirical relations between T c and the zero-temperature superfluid density, ρ s (0), related to the zero-temperature magnetic field penetration depth λ (0) in terms of ρ s (0) ∝ λ −2 (0). In various families of underdoped cuprate superconductors there is the empirical relation T c ∝ ρ s (0) ∝ λ −2 (0), first identified by Uemura et al. [4,5], while in molecular superconductors, T c ∝ λ −3 (0), appears to apply [6]. Both scaling forms appear to have no counterpart in the BCS scenario and even in more conventional superconductors, including Mg 1−x Al x B 2 , Mg(C x B 1−x ) 2 , and MgB 2+x , such relationships remain to be explored. According to the theory of quantum critical phenomena a power law relation between T c and ρ s (0) ∝ λ −2 (0) is expected whenever there is a critical line T c (x) with a critical endpoint x = x c [7,8,9]. Here the transition temperature vanishes and a quantum phase transition occurs.x denotes the tuning parameter of the transition. A variety of underdoped cuprate superconductors exhibits such a critical line, ending at the quantum superconductor to insulator (QSI) transition, where the materials become essentially two dimensional [10]. If the finite tempera-ture behavior in this regime is controlled by the 3D − xy critical point, T c and ρ s (0) scale as [7,8,9] T c ∝ ρ s (0) z/(D+z−2) .(2) z denotes the dynamic critical exponent of the quantum transition in D dimensions. For D = 2 we recover the empirical Uemura relation, T c ∝ ρ s (0) [4,5], irrespective of the value of z.

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“…On the other hand enormous efforts are made to improve the superconducting properties of MgB 2 so that it can be brought on the platform of application. In order to achieve the enhanced properties, as in case of cuprate superconductors, the range of different substituents such as Al, Li, Si, Zr, Cu [13], Sc [14][15][16], Nb, Mn, Fe, Sn, Co [17], Ni, Ag, Au [18], Ca [19] at Mg sites and C, Be [20], F [21], Cr [22] at B sites, were tried. Out of these, only for Zn doping the transition temperature increased or nearly remained the same [23,24]; otherwise the rest of them led to a considerable decrease in T c .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

Sinha

Chung

Pawar

et al. 2011

J Supercond Nov Magn

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A systematic study on the synthesis of carbondoped MgB 2 superconductor, using a new approach wherein the sample was treated under both pressed carbon environment as well as flowing argon, is presented. The sample synthesized was found to be compact and showed cannibalistic surface morphology. Carbon doping in the sample, crystallized in hexagonal structure, accounted for the reduced inplane lattice parameter of 3.06 Å. The intraband scattering due to doping of carbon resulted in a decreased superconducting transition at about 29 K. The behavior of resistivity with respect to a decrease in temperature was embedded in the signatures for the scattering of electrons by phonons as well as the grain boundary impurity in the sample. The carbon doping achieved by the proposed synthesis technique showed improvement in the self-field critical current density up to around 10 5 A/cm 2 at 5 K. The flux-pinning plots were studied to understand the dominant pinning mechanism in the sample.

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Structural and superconducting properties ofMgB2−xBex

Cited by 27 publications

References 18 publications

Synthesis and search for superconductivity in LiBC

Synthesis and search for superconductivity in LiBC

Quantum Superconductor-Metal Transition in Al, C doped MgB2 and Overdoped Cuprates?

Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

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