Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio

Tsung Han Lee; Andrey Chubukov; Hu Miao; Gabriel Kotliar

doi:10.1103/PhysRevLett.121.187003

Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio

Tsung Han Lee, Andrey Chubukov, Hu Miao, Gabriel Kotliar

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Article › peer-review

27 Scopus citations

Abstract

We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, (Ω0/|Ω|)γ, with γ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the 2Δmax/kBTc remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).

Original language	English (US)
Article number	187003
Journal	Physical review letters
Volume	121
Issue number	18
DOIs	https://doi.org/10.1103/PhysRevLett.121.187003
State	Published - Nov 1 2018

Bibliographical note

Funding Information:
T.-H.L. and G.K. were supported by the NSF Grant No. DMR-1733071. A.C. was supported by the NSF Grant No. DMR-1523036. H.M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478.

Funding Information:
In this work, we build on the recent understanding of the physics of the Hund’s metal and studied a phenomenological γ -model describing the superconductivity mediated by a bosonic propagator with a power-law frequency dependence, λ ( Ω ) ∝ 1 / | Ω | γ . This model captures the essence of the transition from a Hund’s metal to a superconductor at a temperature comparable to or higher than a crossover temperature between non-Fermi-liquid and Fermi-liquid behavior [9,11] . We use the model to explore the main characteristics of the pairing gap and T c , ignoring the complications such as the multiorbital or multiband structure of FeSCs. We find 2 Δ max / T c to be independent of the interaction strength and equal to 7.2–7.3 if we use γ = 1.2 obtained from the three-band Hubbard model. These results are in surprisingly good agreement with recent experiments which argued that 2 Δ max / T c ≈ 7.2 is the same in at least two FeSCs: LiFeAs and FeTe 0.55 Se 0.45 [14] . It would be interesting to extend these observations to a more realistic description of the materials, taking into account the multiorbital nature of the problem, and the fact that, in Hund’s metals, the power-law behavior of local spin susceptibility holds in an intermediate temperature range between a Fermi-liquid regime at low temperatures and a high temperature regime where the orbitals and the spins are both quasi-atomic-like. We would like to thank Ar. Abanov, K. Haule, K. Stadler, J. VonDelft, and Y. Wu for numerous discussions on the subject of Hund’s metals and superconductivity in the γ -model. T.-H. L. and G. K. were supported by the NSF Grant No. DMR-1733071. A. C. was supported by the NSF Grant No. DMR-1523036. H. M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478. [1] 1 Y. Kamihara , T. Watanabe , M. Hirano , and H. Hosono , J. Am. Chem. Soc. 130 , 3296 ( 2008 ). 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@article{61b4e0deb06a4c52bf8a042e397daa21,

title = "Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio",

abstract = "We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, (Ω0/|Ω|)γ, with γ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the 2Δmax/kBTc remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).",

author = "Lee, {Tsung Han} and Andrey Chubukov and Hu Miao and Gabriel Kotliar",

note = "Funding Information: T.-H.L. and G.K. were supported by the NSF Grant No. DMR-1733071. A.C. was supported by the NSF Grant No. DMR-1523036. H.M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478. Funding Information: In this work, we build on the recent understanding of the physics of the Hund{\textquoteright}s metal and studied a phenomenological γ -model describing the superconductivity mediated by a bosonic propagator with a power-law frequency dependence, λ ( Ω ) ∝ 1 / | Ω | γ . This model captures the essence of the transition from a Hund{\textquoteright}s metal to a superconductor at a temperature comparable to or higher than a crossover temperature between non-Fermi-liquid and Fermi-liquid behavior [9,11] . We use the model to explore the main characteristics of the pairing gap and T c , ignoring the complications such as the multiorbital or multiband structure of FeSCs. We find 2 Δ max / T c to be independent of the interaction strength and equal to 7.2–7.3 if we use γ = 1.2 obtained from the three-band Hubbard model. These results are in surprisingly good agreement with recent experiments which argued that 2 Δ max / T c ≈ 7.2 is the same in at least two FeSCs: LiFeAs and FeTe 0.55 Se 0.45 [14] . It would be interesting to extend these observations to a more realistic description of the materials, taking into account the multiorbital nature of the problem, and the fact that, in Hund{\textquoteright}s metals, the power-law behavior of local spin susceptibility holds in an intermediate temperature range between a Fermi-liquid regime at low temperatures and a high temperature regime where the orbitals and the spins are both quasi-atomic-like. We would like to thank Ar. Abanov, K. Haule, K. Stadler, J. VonDelft, and Y. Wu for numerous discussions on the subject of Hund{\textquoteright}s metals and superconductivity in the γ -model. T.-H. L. and G. K. were supported by the NSF Grant No. DMR-1733071. A. C. was supported by the NSF Grant No. DMR-1523036. H. M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478. [1] 1 Y. Kamihara , T. Watanabe , M. Hirano , and H. Hosono , J. Am. Chem. Soc. 130 , 3296 ( 2008 ). JACSAT 0002-7863 10.1021/ja800073m [2] 2 J. Paglione and R. L. Greene , Nat. Phys. 6 , 645 ( 2010 ). NPAHAX 1745-2473 10.1038/nphys1759 [3] 3 D. C. Johnston , Adv. Phys. 59 , 803 ( 2010 ). ADPHAH 0001-8732 10.1080/00018732.2010.513480 [4] 4 Q. Si and E. Abrahams , Phys. Rev. Lett. 101 , 076401 ( 2008 ). PRLTAO 0031-9007 10.1103/PhysRevLett.101.076401 [5] 5 P. Werner , E. Gull , M. Troyer , and A. J. Millis , Phys. Rev. Lett. 101 , 166405 ( 2008 ). PRLTAO 0031-9007 10.1103/PhysRevLett.101.166405 [6] 6 K. Haule and G. Kotliar , New J. Phys. 11 , 025021 ( 2009 ). NJOPFM 1367-2630 10.1088/1367-2630/11/2/025021 [7] 7 A. 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year = "2018",

month = nov,

day = "1",

doi = "10.1103/PhysRevLett.121.187003",

language = "English (US)",

volume = "121",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "18",

}

TY - JOUR

T1 - Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio

AU - Lee, Tsung Han

AU - Chubukov, Andrey

AU - Miao, Hu

AU - Kotliar, Gabriel

N1 - Funding Information: T.-H.L. and G.K. were supported by the NSF Grant No. DMR-1733071. A.C. was supported by the NSF Grant No. DMR-1523036. H.M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478. Funding Information: In this work, we build on the recent understanding of the physics of the Hund’s metal and studied a phenomenological γ -model describing the superconductivity mediated by a bosonic propagator with a power-law frequency dependence, λ ( Ω ) ∝ 1 / | Ω | γ . This model captures the essence of the transition from a Hund’s metal to a superconductor at a temperature comparable to or higher than a crossover temperature between non-Fermi-liquid and Fermi-liquid behavior [9,11] . We use the model to explore the main characteristics of the pairing gap and T c , ignoring the complications such as the multiorbital or multiband structure of FeSCs. We find 2 Δ max / T c to be independent of the interaction strength and equal to 7.2–7.3 if we use γ = 1.2 obtained from the three-band Hubbard model. These results are in surprisingly good agreement with recent experiments which argued that 2 Δ max / T c ≈ 7.2 is the same in at least two FeSCs: LiFeAs and FeTe 0.55 Se 0.45 [14] . It would be interesting to extend these observations to a more realistic description of the materials, taking into account the multiorbital nature of the problem, and the fact that, in Hund’s metals, the power-law behavior of local spin susceptibility holds in an intermediate temperature range between a Fermi-liquid regime at low temperatures and a high temperature regime where the orbitals and the spins are both quasi-atomic-like. We would like to thank Ar. Abanov, K. Haule, K. Stadler, J. VonDelft, and Y. Wu for numerous discussions on the subject of Hund’s metals and superconductivity in the γ -model. T.-H. L. and G. K. were supported by the NSF Grant No. DMR-1733071. A. C. was supported by the NSF Grant No. DMR-1523036. H. M. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program under Award No. 1047478. [1] 1 Y. Kamihara , T. Watanabe , M. Hirano , and H. Hosono , J. Am. Chem. Soc. 130 , 3296 ( 2008 ). JACSAT 0002-7863 10.1021/ja800073m [2] 2 J. Paglione and R. L. Greene , Nat. Phys. 6 , 645 ( 2010 ). NPAHAX 1745-2473 10.1038/nphys1759 [3] 3 D. C. Johnston , Adv. Phys. 59 , 803 ( 2010 ). ADPHAH 0001-8732 10.1080/00018732.2010.513480 [4] 4 Q. Si and E. Abrahams , Phys. Rev. Lett. 101 , 076401 ( 2008 ). PRLTAO 0031-9007 10.1103/PhysRevLett.101.076401 [5] 5 P. Werner , E. Gull , M. Troyer , and A. J. Millis , Phys. Rev. Lett. 101 , 166405 ( 2008 ). PRLTAO 0031-9007 10.1103/PhysRevLett.101.166405 [6] 6 K. Haule and G. Kotliar , New J. Phys. 11 , 025021 ( 2009 ). NJOPFM 1367-2630 10.1088/1367-2630/11/2/025021 [7] 7 A. 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PY - 2018/11/1

Y1 - 2018/11/1

N2 - We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, (Ω0/|Ω|)γ, with γ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the 2Δmax/kBTc remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).

AB - We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, (Ω0/|Ω|)γ, with γ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the 2Δmax/kBTc remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).

UR - http://www.scopus.com/inward/record.url?scp=85056108592&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85056108592&partnerID=8YFLogxK

U2 - 10.1103/PhysRevLett.121.187003

DO - 10.1103/PhysRevLett.121.187003

M3 - Article

C2 - 30444397

AN - SCOPUS:85056108592

SN - 0031-9007

VL - 121

JO - Physical Review Letters

JF - Physical Review Letters

IS - 18

M1 - 187003

ER -

Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio

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