Direct observation of the superconducting gap of Sr2RuO4

M. D. Upward; L. P. Kouwenhoven; A. F. Morpurgo; N. Kikugawa; Z. Q. Mao; Y. Maeno

doi:10.1103/PhysRevB.65.220512

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Direct observation of the superconducting gap of Sr2RuO4

M. D. Upward, L. P. Kouwenhoven, A. F. Morpurgo, N. Kikugawa, Z. Q. Mao, Y. Maeno

DOI 10.1103/PhysRevB.65.220512 · Physical Review B

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Abstract

We report the direct observation of the superconducting gap of Sr2RuO4, by means of tunnelling spectroscopy. The tunneling conductance parallel to the c axis was measured using a scanning tunneling microscope operating in a dilution refrigerator. Our results show a suppression in the density of states of Sr2RuO4, which disappears at temperatures higher than Tc or in the presence of a magnetic field larger than the critical field. This demonstrates that superconductivity persists up to the crystal surface and allows us to infer a lower limit of 8.0 for 2Δmax/kTc in the bulk. We attribute this large value to a strong in-plane anisotropy of the gap.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Sr2RuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.42	Pressure not reported	onset
Sr2RuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.5	Pressure not reported	unknown