Two-band Ginzburg Landau theory for the lower critical fieldHc1in MgB2

Askerzade, I. N.; Gençer, A.; Güçlü, N.; Kılıç, Ahmet

doi:10.1088/0953-2048/15/6/101

Cited by 46 publications

(15 citation statements)

References 20 publications

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“…As shown, the situation is very different for the lower critical field which is al-most linear for H ab and reveals a negative curvature for H c at high temperatures. This unusual negative curvature of H c1 c close to T c has been previously observed in thin films and polycrystalline samples [12] and can be explained by the two-band Ginzburg-Landau theory [13] (the isotropic Ginzburg-Landau theory only allows for a linear temperature dependence of H c1 close to T c [14]). As shown below, this difference in curvatures will lead to an increase of Γ λ for increasing temperature.…”

supporting

confidence: 67%

Anisotropies of the Lower and Upper Critical Fields inMgB2Single Crystals

et al. 2004

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The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

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supporting

confidence: 67%

Anisotropies of the Lower and Upper Critical Fields inMgB2Single Crystals

et al. 2004

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“…We note that the temperature dependence of H c1 is somewhat different among different samples. The observed variety in the temperature dependence of lower critical field in different samples may be a consequence of multigap superconductivity, which is known to produce additional structure in the temperature dependence of H c1 [36]. One may expect that the curvature of H c1 is set by the way disorder tunes the contribution of different bands.…”

Section: A Lower Critical Field Hc1mentioning

confidence: 99%

Superfluid density and carrier concentration across a superconducting dome: The case of strontium titanate

et al. 2017

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We present a study of the lower critical field, Hc1, of SrTi1−xNbxO3 as a function of carrier concentration with the aim of quantifying the superfluid density. At low carrier concentration (i.e. the underdoped side), superfluid density and the carrier concentration in the normal state are equal within experimental margin. A significant deviation between the two numbers starts at optimal doping and gradually increases with doping. The inverse of the penetration depth and the critical temperature follow parallel evolutions as in the case of cuprate superconductors. In the overdoped regime, the zero-temperature superfluid density becomes much lower than the normal-state carrier density before vanishing all together. We show that the density mismatch and the clean-to-dirty crossover are concomitant. Our results imply that the discrepancy between normal and superconducting densities is expected whenever the superconducting gap becomes small enough to put the system in the dirty limit. A quantitative test of the dirty BCS theory is not straightforward, due to he multiplicity of the bands in superconducting strontium titanate.

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“…The Helmholtz free energy of Ginzburg and Landau [1] theory can be modified to describe the critical magnetic field in non-magnetic superconductors and magnetic superconductors both in one-band and twoband presented in Refs. [1][2][3][4][5][6][7][8][9][10][26][27][28]. For isotropic two-band GL theory, there are two order parameters in the Ginzburg-Landau functional that free energy can be written down as…”

Section: Model and Calculationsmentioning

confidence: 99%

The critical magnetic field of anisotropic two-band magnetic superconductors

Changjan¹,

Udomsamuthirun²

2011

Solid State Communications

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The upper and lower critical field, and the critical field ratio of an anisotropic two-band magnetic superconductors in Ginzburg-Landau(GL) scenery is derived analytically. The temperature-dependent on the upper critical field is investigated and applied to Fe-based superconductors. We find that the very high value of zero-temperature upper critical field in Febased superconductors can be found in the negative differential susceptibility region. The temperature-dependent upper critical field is presented in two formulas as in the empirical view and in the GL two-band view that agrees with the experiment results.

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Two-band Ginzburg Landau theory for the lower critical fieldH_c1in MgB₂

Cited by 46 publications

References 20 publications

Anisotropies of the Lower and Upper Critical Fields inMgB2Single Crystals

Anisotropies of the Lower and Upper Critical Fields inMgB2Single Crystals

Superfluid density and carrier concentration across a superconducting dome: The case of strontium titanate

The critical magnetic field of anisotropic two-band magnetic superconductors

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