Self-Consistent Two-Gap Description of MgB2 Superconductor

Kim, Hyunsoo; Cho, Kyuil; Tanatar, M. A.; Taufour, Valentin; Kim, Stella K.; Bud’ko, Sergey L.; Canfield, Paul C.; Kogan, V. G.; Prozorov, Ruslan

doi:10.3390/sym11081012

Cited by 16 publications

(15 citation statements)

References 45 publications

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“…We also observed two-bands i.e. π band and σ band having two different SC-energy band gaps with the same critical temperature of 39.1 K from our theoretical model calculation and the gap ratio is approximately the same as experimentally and theoretically observed value [30][31][32][33]38].…”

Section: Resultssupporting

confidence: 78%

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)

Sahoo¹,

Mishra²,

Das³

et al. 2021

AJPA

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We formulate a Model Hamiltonian of two band superconductivity for Magnesium Diboride superconductors (MgB 2 ). It is a conventional BCS type metallic superconductor which has the highest critical temperature T c =39K. It is assumed that the superconductivity in MgB 2 arises due to metallic nature of the 2D sheets. From band structure calculations, it is observed that two types of bands i.e. σ and π bands are located at Fermi surface. Here, we consider phonon mediated superconductivity in which σ band is dominant over π band i.e. σ band is more coupled to a superconductor with much higher coupling. We consider a model Hamiltonian with mean field approach and solve this by calculating equations of motion of Green functions for a single particle. We determine the quasi-particle energy from the poles of the Green functions. We derive the single particle correlation functions and determine the two SC order parameters for both σ and π band. Here, the two SC order parameters for the bands are solved self-consistently and numerically. The conduction bandwidth (W) is considered as W=8t 0 , where t 0 is the hopping integral. To make all the physical quantities dimensionless, we divide 2t 0 in each of the physical quantities. We then calculate the gap ratio 2∆(0)/K B T c for both the bands. It is seen form our theoretical model that the two bands of MgB 2 superconductors have two different SC gaps with the same critical temperature. We also observe the variation of dispersion curves of quasi-particles for different temperature parameters for both σ and π band.

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Section: Resultssupporting

confidence: 78%

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)

Sahoo¹,

Mishra²,

Das³

et al. 2021

AJPA

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“…The black dashed line guides the eye to two linear fits with different slopes, which can correspond to the two isotropic gaps on the FSs. A similar behavior of the Sommerfield coefficient was observed for popular multigap superconductor such as MgB 2 [48,49], 2H-NbSe 2 [50]. Such a nontrivial nature of γ suggests the presence of an unconventional single-particle energy gap, as predicted by the theoretical results [51][52][53].…”

supporting

confidence: 69%

Time-reversal symmetry breaking in frustrated superconductor Re$_2$Hf

Manda,

Kataria,

Patra

et al. 2022

Preprint

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Geometrical frustration leads to novel quantum phenomena such as the spin-liquid phase in triangular and Kagomé lattices. Intra-band and inter-band Fermi surface (FS) nesting can drive unique superconducting (SC) ground states with d-wave and s ± pairing symmetries, respectively, according to the criterion that the SC gap changes sign across the nesting wavevector. For an odd number of FSs, when multiple inter-band nesting is of comparable strength, the sign-reversal criterion between different FS sheets can leads to frustration, which promotes novel SC order parameters. Here we report the experimental observation of a time-reversal symmetry breaking pairing state in Re2Hf resulting from FS nesting frustration. Furthermore, our electronic specific heat and transverse-field µSR experiments suggest a fully gaped pairing symmetry. The first-principle electronic structure calculation reveals multiple Fermi surface sheets with comparable inter-band nesting strength. Implementing the ab-initio band structure, we compute spin-fluctuation mediated SC pairing symmetry which reveals a s + is -pairing state -consistent with experimental observations. Our investigation demonstrates a novel SC state which provides a putative setting for both applied and fundamental study.

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“…Such behavior is expected in the case of multiband superconductors. It is confirmed theoretically as well as experimentally for the most famous two-gap superconductor MgB 2 [32,41,[54][55][56].…”

Section: B C E (T ) and B C (T ) Of Beau: Two-gap Scenariomentioning

confidence: 53%

“…Measurements of temperature dependences of thermodynamic quantities such as the superfluid density ρ s , the electronic specific heat C e , and the thermodynamic critical field B c are among the primary ways used to test pairing mechanisms of new superconductors [1][2][3][4][5][6]. In particular, such experiments allow us (i) to distinguish between the single-band and multiband scenarios [7][8][9][10][11][12][13][14], (ii) to determine the superconducting gap structure [15][16][17][18][19][20][21][22][23][24][25][26], (iii) to calculate the temperature evolution(s) of the superconducting energy gaps [27][28][29][30][31][32][33], etc. Obviously, the parameters obtained from the analysis of various thermodynamic quantities need to be consistent with each other.…”

Section: Introductionmentioning

confidence: 99%

Single-gap versus two-gap scenario: Specific heat and thermodynamic critical field of the noncentrosymmetric superconductor BeAu

et al. 2020

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Temperature evolutions of the electronic specific heat C e (T ) [A. Amon et al., Phys. Rev. B 97, 014501 (2018)] and the thermodynamic critical field B c (T ) [R. Khasanov et al., Phys. Rev. Research 2, 023142 (2020)] of the BeAu superconductor were reconsidered within the framework of the single-gap and two-gap scenarios. The analysis shows that the single-gap approach, by being able to describe satisfactorily the temperature dependence of C e (T ), fails in the case of B c (T ). The self-consistent two-gap model, in contrast, is able to describe both thermodynamic quantities by using a similar set of parameters. Our results imply that in some particular cases, such as in the case of BeAu, measurement of one single thermodynamic quantity may not be enough in order to speculate on the nature of the superconducting pairing mechanism.

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Self-Consistent Two-Gap Description of MgB2 Superconductor

Cited by 16 publications

References 45 publications

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)

Time-reversal symmetry breaking in frustrated superconductor Re$_2$Hf

Single-gap versus two-gap scenario: Specific heat and thermodynamic critical field of the noncentrosymmetric superconductor BeAu

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Self-Consistent Two-Gap Description of MgB2 Superconductor

Cited by 16 publications

References 45 publications

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB&lt;sub&gt;2&lt;/sub&gt;)

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB&lt;sub&gt;2&lt;/sub&gt;)

Time-reversal symmetry breaking in frustrated superconductor Re$_2$Hf

Single-gap versus two-gap scenario: Specific heat and thermodynamic critical field of the noncentrosymmetric superconductor BeAu

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Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)

Microscopic Study of Two Band Superconductivity in Magnesium Diboride Superconductor (MgB<sub>2</sub>)