Coherence Lengths for Superconductivity in the Two-Orbital Negative-U Hubbard Model

Litak, Grzegorz; Örd, T.; Rägo, Küllike; Vargunin, Artjom

doi:10.12693/aphyspola.121.747

Cited by 18 publications

(46 citation statements)

References 22 publications

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“…This fact is illustrated in Fig. (1), where it is given the qualitative picture of calculations in [3]. Phase relations (8) imposes restrictions on the coefficient η.…”

Section: Two-band Superconductormentioning

confidence: 95%

Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

Grigorishin

2016

Physics Letters A

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It has been shown that interband mixing of gradients of two order parameters (drag effect) in an isotropic bulk two-band superconductor plays important role -such a quantity of the intergradients coupling exists that the two-band superconductor is characterized with a single coherence length and a single Ginzburg-Landau (GL) parameter. Other quantities or neglecting of the drag effect lead to existence of two coherence lengths and dynamical instability due to violation of the phase relations between the order parameters. Thus so-called type-1.5 superconductors are impossible. An approximate method for solving of set of GL equations for a multi-band superconductor has been developed: using the result about the drag effect it has been shown that the free-energy functional for a multi-band superconductor can be reduced to the GL functional for an effective single-band superconductor.

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“…This fact is illustrated in Fig. (1), where it is given the qualitative picture of calculations in [3]. Phase relations (8) imposes restrictions on the coefficient η.…”

Section: Two-band Superconductormentioning

confidence: 95%

Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

Grigorishin

2016

Physics Letters A

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“…8,9 Two distinct correlation lengths are also present in the negative-U Hubbard model of two-orbital superconductivity. 10 In this respect, the connection between peculiarities of spatial coherency and excitation of the Leggett mode in two-gap material was discussed. 11 Different point of view on the correlation behavior in a two-band model is based on the statement that two order parameters should have identical characteristic lengths of spatial variation by approaching critical temperature.…”

Section: Introductionmentioning

confidence: 99%

Correlation functions and coherence lengths in a two-gap superconductor

Vargunin

Örd

2012

Phys. Rev. B

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We derive analytically the spatial correlation functions for gap fluctuations in a two-band scenario with intraband and interband pair-transfer interactions. These functions demonstrate the changes in functionality due to the presence of two channels of coherency described by the divergent and finite correlation lengths. Even at the phase transition point, both channels are essential for two-band superconductivity. Generally, their relative contributions depend on the temperature and system parameters.

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“…In a case of the contact of two metal the critical temperature of the source drops, however in a case of the multi-band superconductor the proximity effect supports superconducting state in all bands. k B T c2 < 2∆ 1 k B T c1 as it can be in two-band superconductors [6,7]. The gap ∆3(T ) asymptotically aspires to zero as temperature rises, so that 2∆ 3 k B T c3 = 0.…”

Section: Introductionmentioning

confidence: 94%

“…-quasiaverages Bogolyubov method. In the other case the operator can have a U (1) × U (1) symmetrical form k υa + k↑ a + −k↓ + υ + a −k↓ a k↑ , where υ is the order parameter of another superconductor, for example, the boundary (proximity) effect, when a superconductor is placed in contact with a normal metal [3] or interband mixing of two order parameters belonging to different bands in a multi-band superconductor [5][6][7] occurs.…”

Section: The Modelmentioning

confidence: 99%

“…In this cases the Cooper pairs are injected into the superconductor (band) from another superconductor (band) with higher critical temperature (stronger interaction) which plays a role of a source of Cooper pairs. As a result in a band with lower critical temperature the ratio (1) can be violated as k B T c > ∆ [6,7] as illustrated in Fig.(1). However the source is function of temperature with own critical temperature.…”

Section: Introductionmentioning

confidence: 99%

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BCS theory with the external pair potential

Grigorishin

2017

Physics Letters A

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-b Metrolohichna str. Kiev-03680, Ukraine.We consider a hypothetical substance, where interaction between (within) structural elements of condensed matter (molecules, nanoparticles, clusters, layers, wires etc.) depends on state of Cooper pairs: an additional work must be made against this interaction to break a pair. Such a system can be described by BCS Hamiltonian with the external pair potential term. In this model the potential essentially renormalizes the order parameter: if the pairing lowers energy of the structure the energy gap is slightly enlarged at zero temperature and asymptotically tends to zero as temperature rises. Thus the critical temperature of such a superconductor is equal to infinity formally. For this case the effective Ginzburg-Landau theory is formulated, where the coherence length decreases as temperature rises, the GL parameter and the second critical field are increasing functions of temperature unlike the standard theory. If the pairing enlarges energy of the structure then suppression of superconductivity and the first order phase transition occur.

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Coherence Lengths for Superconductivity in the Two-Orbital Negative-U Hubbard Model

Cited by 18 publications

References 22 publications

Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

Correlation functions and coherence lengths in a two-gap superconductor

BCS theory with the external pair potential

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