skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}

Abstract

In 1980, Binnig et al. reported tunneling measurements on Nb-doped SrTiO{sub 3}, and interpreted their results as indicating two-band superconductivity in the bulk of SrTiO{sub 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{sub 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{sub c} to the actual T{sub c}. We show results for a combined fitmore » 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{sub cmf}/T{sub 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{sub cmf}/T{sub c}.« less

Authors:
Publication Date:
OSTI Identifier:
22776964
Resource Type:
Journal Article
Journal Name:
Journal of Superconductivity and Novel Magnetism
Additional Journal Information:
Journal Volume: 31; Journal Issue: 4; Other Information: Copyright (c) 2018 Springer Science+Business Media, LLC, part of Springer Nature; Article Copyright (c) 2017 Springer Science+Business Media, LLC; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1557-1939
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTALS; DOPED MATERIALS; MEAN-FIELD THEORY; MEV RANGE; NIOBIUM; PHONONS; STRONTIUM TITANATES; SUPERCONDUCTIVITY; SURFACES; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K; TUNNEL EFFECT

Citation Formats

Eagles, D. M., E-mail: d.eagles@ic.ac.uk. Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}. United States: N. p., 2018. Web. doi:10.1007/S10948-017-4289-9.
Eagles, D. M., E-mail: d.eagles@ic.ac.uk. Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}. United States. doi:10.1007/S10948-017-4289-9.
Eagles, D. M., E-mail: d.eagles@ic.ac.uk. Sun . "Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}". United States. doi:10.1007/S10948-017-4289-9.
@article{osti_22776964,
title = {Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}},
author = {Eagles, D. M., E-mail: d.eagles@ic.ac.uk},
abstractNote = {In 1980, Binnig et al. reported tunneling measurements on Nb-doped SrTiO{sub 3}, and interpreted their results as indicating two-band superconductivity in the bulk of SrTiO{sub 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{sub 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{sub c} to the actual T{sub 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{sub cmf}/T{sub 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{sub cmf}/T{sub c}.},
doi = {10.1007/S10948-017-4289-9},
journal = {Journal of Superconductivity and Novel Magnetism},
issn = {1557-1939},
number = 4,
volume = 31,
place = {United States},
year = {2018},
month = {4}
}