Tunneling spectroscopy of the superconducting gap in MgB2

Toshikazu Ekino; Tomoaki Takasaki; Takahiro Muranaka; Jun Akimitsu; Hironobu Fujii

doi:10.1103/PhysRevB.67.094504

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Tunneling spectroscopy of the superconducting gap in MgB2

Toshikazu Ekino, Tomoaki Takasaki, Takahiro Muranaka, Jun Akimitsu, Hironobu Fujii

DOI 10.1103/PhysRevB.67.094504 · Physical Review B

T1

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Abstract

The tunneling technique with a break junction has been applied to investigate the multiple superconducting gaps in MgB2. The observed gap features can be explained by combining inherent and induced order parameters. The largest gap of Δ=9–10meV corresponds to a very strong-coupling ratio 2Δ/kBTc=5–6. Upon warming, this gap decreases in accordance with the BCS dependence, while the smaller gaps reduce faster than that but persist up to Tc. Therefore, the smallest gap of Δ=2–2.5meV gives 2Δ/kBTc=1.2–1.5. The magnetic field can distinguish the behavior of the gap. The extrapolated highest gap-closing field for the largest gap agrees with the upper-critical field, thereby indicating that this gap is predominant to MgB2.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39.2	Pressure not reported	onset
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39.2	Pressure not reported	onset
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	unknown