Point-contact spectroscopy of CeCoIn5: Andreev reflection studies of the normal-metal-heavy-fermion superconductor interface

L. H. Greene; W. K. Park; J. L. Sarrao; J. D. Thompson

doi:10.1016/j.physb.2006.01.460

Point-contact spectroscopy of CeCoIn₅: Andreev reflection studies of the normal-metal-heavy-fermion superconductor interface

L. H. Greene, W. K. Park, J. L. Sarrao, J. D. Thompson

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

Abstract

Point-contact spectroscopy (PCS) results are obtained with normal-metal (N) Au tips on single crystals of the heavy-fermion superconductor (HFS) CeCoIn₅. Our exceptionally clean, reproducible data are taken over a temperature range of 60 K to 400 mK. Contacts are shown to be in the Sharvin limit. Asymmetry observed in the background conductance starting at T* (∼45 K), increasing with decreasing temperature to T_c (2.3 K), signifies the emerging heavy-fermion liquid. Below T_c, the enhancement of the subgap conductance (∼13.3% at 400 mK) arises from Andreev reflection (AR). According to standard Blonder-Tinkham-Klapwijk (BTK) theory, the Fermi velocity mismatch between an N and a HFS should yield no AR. The AR we do observe is several times lower than that observed in N/conventional superconductor PCS, but consistent with other N-HFS data reported. Our zero-bias conductance data are best fit with an extended d-wave BTK model. A fit to the full conductance curve at 400 mK indicates strong coupling (2Δ/k_BT_c=4.6), but the suppression of both the AR signal and the energy gap cannot be accounted for with existing models.

Original language	English (US)
Pages (from-to)	671-672
Number of pages	2
Journal	Physica B: Condensed Matter
Volume	378-380
Issue number	SPEC. ISS.
DOIs	https://doi.org/10.1016/j.physb.2006.01.460
State	Published - May 1 2006
Externally published	Yes

Keywords

Andreev reflection
Heavy fermions
Point-contact spectroscopy
Superconductivity

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics

Online availability

10.1016/j.physb.2006.01.460

Library availability

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Cite this

@article{79f56a7be5d9428e9c118ef1bd0e5aa2,

title = "Point-contact spectroscopy of CeCoIn5: Andreev reflection studies of the normal-metal-heavy-fermion superconductor interface",

abstract = "Point-contact spectroscopy (PCS) results are obtained with normal-metal (N) Au tips on single crystals of the heavy-fermion superconductor (HFS) CeCoIn5. Our exceptionally clean, reproducible data are taken over a temperature range of 60 K to 400 mK. Contacts are shown to be in the Sharvin limit. Asymmetry observed in the background conductance starting at T* (∼45 K), increasing with decreasing temperature to Tc (2.3 K), signifies the emerging heavy-fermion liquid. Below Tc, the enhancement of the subgap conductance (∼13.3% at 400 mK) arises from Andreev reflection (AR). According to standard Blonder-Tinkham-Klapwijk (BTK) theory, the Fermi velocity mismatch between an N and a HFS should yield no AR. The AR we do observe is several times lower than that observed in N/conventional superconductor PCS, but consistent with other N-HFS data reported. Our zero-bias conductance data are best fit with an extended d-wave BTK model. A fit to the full conductance curve at 400 mK indicates strong coupling (2Δ/kBTc=4.6), but the suppression of both the AR signal and the energy gap cannot be accounted for with existing models.",

keywords = "Andreev reflection, Heavy fermions, Point-contact spectroscopy, Superconductivity",

author = "Greene, {L. H.} and Park, {W. K.} and Sarrao, {J. L.} and Thompson, {J. D.}",

note = "Funding Information: We are grateful to A. J. Leggett, D. Pines, V. Lukic, and J. Elenewski for fruitful discussions and to B. F. Wilken, A. N. Thaler, P. J. Hentges, K. Parkinson, and W. L. Feldmann for experimental help. This work was supported by the US DOE Award no. DEFG02-91ER45439, through FS MRL and CMM at UIUC. ",

year = "2006",

month = may,

day = "1",

doi = "10.1016/j.physb.2006.01.460",

language = "English (US)",

volume = "378-380",

pages = "671--672",

journal = "Physica B: Condensed Matter",

issn = "0921-4526",

publisher = "Elsevier B.V.",

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}

TY - JOUR

T1 - Point-contact spectroscopy of CeCoIn5

T2 - Andreev reflection studies of the normal-metal-heavy-fermion superconductor interface

AU - Greene, L. H.

AU - Park, W. K.

AU - Sarrao, J. L.

AU - Thompson, J. D.

N1 - Funding Information: We are grateful to A. J. Leggett, D. Pines, V. Lukic, and J. Elenewski for fruitful discussions and to B. F. Wilken, A. N. Thaler, P. J. Hentges, K. Parkinson, and W. L. Feldmann for experimental help. This work was supported by the US DOE Award no. DEFG02-91ER45439, through FS MRL and CMM at UIUC.

PY - 2006/5/1

Y1 - 2006/5/1

N2 - Point-contact spectroscopy (PCS) results are obtained with normal-metal (N) Au tips on single crystals of the heavy-fermion superconductor (HFS) CeCoIn5. Our exceptionally clean, reproducible data are taken over a temperature range of 60 K to 400 mK. Contacts are shown to be in the Sharvin limit. Asymmetry observed in the background conductance starting at T* (∼45 K), increasing with decreasing temperature to Tc (2.3 K), signifies the emerging heavy-fermion liquid. Below Tc, the enhancement of the subgap conductance (∼13.3% at 400 mK) arises from Andreev reflection (AR). According to standard Blonder-Tinkham-Klapwijk (BTK) theory, the Fermi velocity mismatch between an N and a HFS should yield no AR. The AR we do observe is several times lower than that observed in N/conventional superconductor PCS, but consistent with other N-HFS data reported. Our zero-bias conductance data are best fit with an extended d-wave BTK model. A fit to the full conductance curve at 400 mK indicates strong coupling (2Δ/kBTc=4.6), but the suppression of both the AR signal and the energy gap cannot be accounted for with existing models.

AB - Point-contact spectroscopy (PCS) results are obtained with normal-metal (N) Au tips on single crystals of the heavy-fermion superconductor (HFS) CeCoIn5. Our exceptionally clean, reproducible data are taken over a temperature range of 60 K to 400 mK. Contacts are shown to be in the Sharvin limit. Asymmetry observed in the background conductance starting at T* (∼45 K), increasing with decreasing temperature to Tc (2.3 K), signifies the emerging heavy-fermion liquid. Below Tc, the enhancement of the subgap conductance (∼13.3% at 400 mK) arises from Andreev reflection (AR). According to standard Blonder-Tinkham-Klapwijk (BTK) theory, the Fermi velocity mismatch between an N and a HFS should yield no AR. The AR we do observe is several times lower than that observed in N/conventional superconductor PCS, but consistent with other N-HFS data reported. Our zero-bias conductance data are best fit with an extended d-wave BTK model. A fit to the full conductance curve at 400 mK indicates strong coupling (2Δ/kBTc=4.6), but the suppression of both the AR signal and the energy gap cannot be accounted for with existing models.

KW - Andreev reflection

KW - Heavy fermions

KW - Point-contact spectroscopy

KW - Superconductivity

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U2 - 10.1016/j.physb.2006.01.460

DO - 10.1016/j.physb.2006.01.460

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JO - Physica B: Condensed Matter

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