Crossband versus intraband pairing in superconductors: Signatures and consequences of the interplay

Vargas-Paredes, Alfredo A.; Shanenko, A. A.; Vagov, Alexei; Miloševıć, M. V.; Perali, Andrea

doi:10.1103/physrevb.101.094516

Cited by 28 publications

(17 citation statements)

References 69 publications

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“…It would be interesting to extend the present study to other FeSC families (e.g., 112 70 , 10-3-8 and 10-4-8 71 – 73 , for which a possible quasi-2D behavior 29 may also affect the angular dependence), and to probe signatures of crossband pairing, that could be present in these materials, as it has been recently proposed 74 .…”

Section: Discussionmentioning

confidence: 83%

Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors

Llovo

Carballeira

Sóñora

et al. 2021

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Detailed measurements of the in-plane resistivity were performed in a high-quality Ba($$\hbox {Fe}_{1-x}\hbox {Co}_{{x}}$$ Fe 1 - x Co x )$$_2\hbox {As}_2$$ 2 As 2 ($$x=0.065$$ x = 0.065 ) single crystal, in magnetic fields up to 9 T and with different orientations $$\theta$$ θ relative to the crystal c axis. A significant $$\rho (T)_{H,\theta }$$ ρ ( T ) H , θ rounding is observed just above the superconducting critical temperature $$T_c$$ T c due to Cooper pairs created by superconducting fluctuations. These data are analyzed in terms of a generalization of the Aslamazov-Larkin approach, that extends its applicability to high reduced-temperatures and magnetic fields. This method allows us to carry out a criterion-independent determination of the angular dependence of the upper critical field, $$H_{c2}(\theta )$$ H c 2 ( θ ) . In spite of the relatively small anisotropy of this compound, it is found that $$H_{c2}(\theta )$$ H c 2 ( θ ) presents a significant deviation from the single-band 3D anisotropic Ginzburg-Landau (3D-aGL) approach, particularly for large $$\theta$$ θ (typically above $$\sim 60^o$$ ∼ 60 o ). These results are interpreted in terms of the multiband nature of these materials, in contrast with other proposals for similar $$H_{c2}(\theta )$$ H c 2 ( θ ) anomalies. Our results are also consistent with an effective anisotropy factor almost temperature independent near $$T_c$$ T c , a result that differs from the ones obtained by using a single-band model.

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Section: Discussionmentioning

confidence: 83%

Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors

Llovo

Carballeira

Sóñora

et al. 2021

Sci Rep

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“…In contrast with conventional BCS pairing, the Coulomb pairing interaction is independent of the electron and hole spins. There are four possible electron-hole pairings, corresponding to four superfluid condensates [37,38]. We introduce the temperature dependent normal and anomalous multiband Matsubara Green functions, with subband indices α and β,…”

Section: Methodsmentioning

confidence: 99%

“…where T τ is the time-ordering operator. These result in mean field equations for the gaps and the densities [37,38]:…”

Section: Methodsmentioning

confidence: 99%

Transition Metal Dichalcogenides as Strategy for High Temperature Electron-Hole Superfluidity

et al. 2020

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Condensation of spatially indirect excitons, with the electrons and holes confined in two separate layers, has recently been observed in two different double layer heterostructures. High transition temperatures were reported in a double Transition Metal Dichalcogenide (TMD) monolayer system. We briefly review electron-hole double layer systems that have been proposed as candidates for this interesting phenomenon. We investigate the double TMD system WSe 2 /hBN/MoSe 2 , using a mean-field approach that includes multiband effects due to the spin-orbit coupling and self-consistent screening of the electron-hole Coulomb interaction. We demonstrate that the transition temperature observed in the double TMD monolayers, which is remarkably high relative to the other systems, is the result of (i) the large electron and hole effective masses in TMDs, (ii) the large TMD band gaps, and (iii) the presence of multiple superfluid condensates in the TMD system. The net effect is that the superfluidity is strong across a wide range of densities, which leads to high transition temperatures that extend as high as T B K T = 150 K.

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“…A mean-field analysis of the interplay between cross-band and intraband pairing, with applications to iron-based superconductors, has been recently reported in Ref. [42], while the effects of fluctuations and pseudogaps in this complex configuration is still an open and computational demanding problem. However, the shallow Fermi surface pocket coupled to the deep band in these materials, corresponding to the band 2 in this paper, indeed plays a significant role for the realization of the two-band BCS-BEC crossover in FeSe superconductors [7].…”

Section: Formalismmentioning

confidence: 99%

Hidden Pseudogap and Excitation Spectra in a Strongly Coupled Two-Band Superfluid/Superconductor

2021

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We investigate single-particle excitation properties in the normal state of a two-band superconductor or superfluid throughout the Bardeen–Cooper–Schrieffer (BCS) to Bose–Einstein-condensation (BEC) crossover, within the many-body T-matrix approximation for multichannel pairing fluctuations. We address the single-particle density of states and the spectral functions consisting of two contributions associated with a weakly interacting deep band and a strongly interacting shallow band, relevant for iron-based multiband superconductors and multicomponent fermionic superfluids. We show how the pseudogap state in the shallow band is hidden by the deep band contribution throughout the two-band BCS-BEC crossover. Our results could explain the missing pseudogap in recent scanning tunneling microscopy experiments in FeSe superconductors.

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Crossband versus intraband pairing in superconductors: Signatures and consequences of the interplay

Cited by 28 publications

References 69 publications

Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors

Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors

Transition Metal Dichalcogenides as Strategy for High Temperature Electron-Hole Superfluidity

Hidden Pseudogap and Excitation Spectra in a Strongly Coupled Two-Band Superfluid/Superconductor

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