Superconductivity in monolayer FeSe enhanced by quantum geometry

Kitamura, Taisei; Yamashita, Tatsuya; Ishizuka, Jun; Daido, Akito; Yanase, Youichi

doi:10.1103/physrevresearch.4.023232

Cited by 18 publications

(7 citation statements)

References 86 publications

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“…The superfluid weight has been computed from mean field theory in a variety of multiband systems [6,7,13,14,28,34,43,[50][51][52][53] including magic-angle twisted bilayer graphene [23][24][25]. The impact of the terms arising from the derivatives of the order parameters in Eq.…”

Section: Revisiting the Literaturementioning

confidence: 99%

Revisiting flat band superconductivity: Dependence on minimal quantum metric and band touchings

et al. 2022

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A central result in superconductivity is that flat bands, though dispersionless, can still host a nonzero superfluid weight due to quantum geometry. We show that the derivation of the mean field superfluid weight in previous literature is incomplete, which can lead to severe quantitative and even qualitative errors. We derive the complete equations and demonstrate that the minimal quantum metric, the metric with minimum trace, is related to the superfluid weight in isolated flat bands. We complement this result with an exact calculation of the Cooper pair mass in attractive Hubbard models with the uniform pairing condition. When the orbitals are located at high-symmetry positions, the Cooper pair mass is exactly given by the quantum metric, which is guaranteed to be minimal. Moreover, we study the effect of closing the band gap between the flat and dispersive bands, and develop a mean field theory of pairing for different band-touching points via the S-matrix construction. In mean field theory, we show that a nonisolated flat band can actually be beneficial for superconductivity. This is a promising result in the search for high-temperature superconductivity as the material does not need to have flat bands that are isolated from other bands by the thermal energy. Our work resolves a fundamental caveat in understanding the relation of multiband superconductivity to quantum geometry, and the results on band touchings widen the class of systems advantageous for the search of high-temperature flat band superconductivity.

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Section: Revisiting the Literaturementioning

confidence: 99%

Revisiting flat band superconductivity: Dependence on minimal quantum metric and band touchings

et al. 2022

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“…In this paper we dealt with a simplified model for UTe 2 , where the orbital degree of freedom, electron correlation effect, detailed band structure and so on are neglected for simplicity. For a precise prediction it is desirable to study a more realistic model for UTe 2 , as we have carried out for FeSe based on the first-principles calculation 58,62 . Such studies are beyond the scope of this paper and left for a future work.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…In this paper, we show that the anapole superconductivity is a ubiquitous feature more than revealed in the previous paper 28 , considering the quantum geometry extensively studied in various fields 37,38,[47][48][49][50][51][52][53][54][55][56][57][58] . Recently, an essential role of the quantum geometry in the superfluid weight, namely, the second-order derivative of the free energy, has been revealed [59][60][61][62] . Thus, it is naturally expected that the quantum geometry may be essential for the anapole superconductivity.…”

Section: Introductionmentioning

confidence: 99%

Quantum-geometry-induced anapole superconductivity

Kitamura¹,

Kanasugi²,

Chazono³

et al. 2022

Preprint

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Anapole superconductivity recently proposed for multiband superconductors [Commun. Phys. 5, 39 (2022)] is a key feature of time-reversal (T )-symmetry-broken polar superconductors. The anapole moment was shown to arise from the asymmetric Bogoliubov spectrum, which induces a finite center of mass momenta of Cooper pairs at the zero magnetic field. In this paper, we show an alternative mechanism of anapole superconductivity: the quantum geometry induces the anapole moment when the interband pairing and Berry connection are finite. Thus, the anapole superconductivity is a ubiquitous feature of T -broken multiband polar superconductors. Applying the theory to a minimal model of UTe2, we demonstrate the quantum-geometry-induced anapole superconductivity. Furthermore, we show the Bogoliubov Fermi surfaces (BFS) in an anapole superconducting state and predict an unusual temperature dependence of BFS due to the quantum geometry. Experimental verification of these phenomena may clarify the superconducting state in UTe2 and reveal the ubiquitous importance of quantum geometry in exotic superconductors.

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“…Nonetheless, the geometric effect is not unique to flat band systems. Recently, the discussion has been extended to geometry-induced effects, including some peculiar optical anomalies, in a more broad spectrum of multiorbital superconductors [19][20][21][22].…”

mentioning

confidence: 99%

“…Note added. In the process of completing this manuscript, we became aware of a proposal of quantum geometry induced FFLO state in the presence of external magnetic field [28].…”

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confidence: 99%

Pair density wave facilitated by Bloch quantum geometry in nearly flat band multiorbital superconductors

Chen¹,

Wen²

2022

Preprint

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Bloch electrons in multiorbital systems carry quantum geometric information characteristic of their wavevector-dependent interorbital mixing. The geometric nature impacts electromagnetic responses, and this effect carries over to the superconducting state, which receives a geometric contribution to the superfluid weight. In this paper, we show that this contribution could become negative under appropriate circumstances, and that a more striking scenario could occur in the narrow-or flat-band limit when the geometric contribution overcomes the conventional contribution to produce an overall negative superfluid weight. This paves the way for the stabilization of a Cooper pairing that favors real space phase modulation, i.e. the pair density wave order, as we demonstrate through two-orbital model Bogoliubov de-Gennes mean-field calculations. The quantum geometric effect therefore constitutes an intrinsic mechanism for the formation of pair density wave states in the absence of external magnetic field.

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Superconductivity in monolayer FeSe enhanced by quantum geometry

Cited by 18 publications

References 86 publications

Revisiting flat band superconductivity: Dependence on minimal quantum metric and band touchings

Revisiting flat band superconductivity: Dependence on minimal quantum metric and band touchings

Quantum-geometry-induced anapole superconductivity

Pair density wave facilitated by Bloch quantum geometry in nearly flat band multiorbital superconductors

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