Multiband Superconductivity Due to the Electron–LO–Phonon Interaction in Strontium Titanate and on a SrTiO3/LaAlO3 Interface

Klimin, S. N.; Tempere, J.; Devreese, J. T.; Marel, D. van der

doi:10.1007/s10948-016-3664-2

Cited by 7 publications

(15 citation statements)

References 36 publications

(108 reference statements)

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“…The non-parabolic dispersion in SrTiO 3 leads to a rapidly increasing density of states in the range of energies corresponding to Fermi energies for densities up to n ∼ 10 20 cm −3 . This leads to better quantitative agreement of the calculated T c with experimental data than in our preceding work [12]. The contribution of acoustic phonons results in an increase of T c about 25% with a shift of the maximum of superconducting dome to higher densities.…”

Section: Concentration Dependent Critical Temperaturessupporting

confidence: 65%

“…In the present study, spin-orbit coupling and next-nearest-neighbor hopping are neglected. We start from the gap equation [12], where the band dispersion law ε k,λ can be, in general, non-parabolic,…”

Section: Theoretical Descriptionmentioning

confidence: 99%

“…The dispersion of the conduction band is described by the tight-binding analytic fit for the band Hamiltonian using the expressions and notations of Ref. [12]. We apply the values of the diagonal matrix elements t δ , t π from the tight-binding fit to the calculation performed using the GW method [31]: t δ = 54.2 meV, t π = 490.9 meV.…”

Section: Concentration Dependent Critical Temperaturesmentioning

confidence: 99%

“…the concentration-dependent superconducting transition temperature [9,12,13,22]. A verification of the KMK ansatz within the non-adiabatic extension of the Eliashberg theory [11] showed compatibility of these two methods.…”

Section: Introductionmentioning

confidence: 99%

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Superconductivity in SrTiO3: Dielectric Function Method for Non-Parabolic Bands

Klimin

Tempere

Devreese

et al. 2019

J Supercond Nov Magn

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The dielectric function method for superconductivity has been applied to SrTiO3 accounting for the non-parabolic dispersion of charge carriers in the conduction band and for the dispersion of optical phonons based on density functional theory calculations. The obtained critical temperatures of the superconducting phase transition in SrTiO3 are in agreement with experiments in the density range n ∼ 5 × 10 18 to 5 × 10 20 cm −3 . The dielectric function method predicts also the sign of the anomalous isotope effect in strontium titanate, in line with recent observations.

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Section: Concentration Dependent Critical Temperaturessupporting

confidence: 65%

Section: Theoretical Descriptionmentioning

confidence: 99%

Section: Concentration Dependent Critical Temperaturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Superconductivity in SrTiO3: Dielectric Function Method for Non-Parabolic Bands

Klimin

Tempere

Devreese

et al. 2019

J Supercond Nov Magn

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“…Our use of a model where interaction with longitudinal optical phonons dominates the pairing has some support from a paper by Klimin et al [16], who, using a dielectric approach to pairing, find that such phonons dominate the pairing. However, from their paper it is not clear to me the relative importance of the three types of longitudinal polar optical phonons in their theory.…”

Section: Introductionsupporting

confidence: 65%

Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO3

Eagles¹

2017

J Supercond Nov Magn

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In 1980 Binnig et al. reported tunneling measurements on Nb-doped SrTiO 3 , and interpreted their results as indicating two-band superconductivity in the bulk of SrTiO 3 . However: (1) Effective masses determined from tunneling results in the normal state by Sroubek in 1969 and 1970 are much smaller than those determined by most other methods. The much smaller masses were attributed to properties of a surface layer by the present author in 1971; (2) The only other reports of two-band superconductivity in bulk SrTiO 3 can be used to infer much smaller values for the band separations than found by Binnig et al.. In this paper we give an alternative explanation of the results of Binnig et al. in terms of superconductivity in a surface layer. We obtain fair fits to the band gaps versus Fermi energy for the two bands in the three samples where two surface subbands are occupied and to the temperature dependence of the gaps in one crystal, using a model with three adjustable interaction parameters, an adjustable energy for the phonons which dominate the pairing, and an adjustable ratio of the mean-field T c to the actual T c . We show results for a combined fit to the low-temperature band gaps and to the T -dependence in one crystal. The phonon energy which gives the best fit is 21 meV. This is probably an appropriate average over the three longitudinal polar modes and acoustic modes in the material. A large value of about two is found for the ratio T cmf /T c , and we conjecture that this arises because a band with a small Fermi energy, not seen in the tunneling results, plays a part in increasing T cmf /T c .

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Polaronic behavior in a weak-coupling superconductor

Swartz

Inoue

Merz

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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The nature of superconductivity in the dilute semiconductor SrTiO has remained an open question for more than 50 y. The extremely low carrier densities ([Formula: see text]-[Formula: see text] cm) at which superconductivity occurs suggest an unconventional origin of superconductivity outside of the adiabatic limit on which the Bardeen-Cooper-Schrieffer (BCS) and Migdal-Eliashberg (ME) theories are based. We take advantage of a newly developed method for engineering band alignments at oxide interfaces and access the electronic structure of Nb-doped SrTiO, using high-resolution tunneling spectroscopy. We observe strong coupling to the highest-energy longitudinal optic (LO) phonon branch and estimate the doping evolution of the dimensionless electron-phonon interaction strength ([Formula: see text]). Upon cooling below the superconducting transition temperature ([Formula: see text]), we observe a single superconducting gap corresponding to the weak-coupling limit of BCS theory, indicating an order of magnitude smaller coupling ([Formula: see text]). These results suggest that despite the strong normal state interaction with electrons, the highest LO phonon does not provide a dominant contribution to pairing. They further demonstrate that SrTiO is an ideal system to probe superconductivity over a wide range of carrier density, adiabatic parameter, and electron-phonon coupling strength.

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Multiband Superconductivity Due to the Electron–LO–Phonon Interaction in Strontium Titanate and on a SrTiO3/LaAlO3 Interface

Cited by 7 publications

References 36 publications

Superconductivity in SrTiO3: Dielectric Function Method for Non-Parabolic Bands

Superconductivity in SrTiO3: Dielectric Function Method for Non-Parabolic Bands

Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO3

Polaronic behavior in a weak-coupling superconductor

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