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Two-channel point-contact tunneling theory of superconductors

Mikael Fogelström (Institutionen för mikroteknologi och nanovetenskap, Tillämpad kvantfysik) ; Matthias J Graf ; V. A. Sidorov ; Xin Lu ; E. D. Bauer ; J. D. Thompson
Physical Review B. Condensed Matter and Materials Physics (1098-0121). Vol. 90 (2014), 10, p. 104512.
[Artikel, refereegranskad vetenskaplig]

We introduce a two-channel tunneling model to generalize the widely used BTK theory of point-contact conductance between a normal metal contact and superconductor. Tunneling of electrons can occur via localized surface states or directly, resulting in a Fano resonance in the differential conductance G = d I /d V . We present an analysis of G within the two-channel model when applied to soft point contacts between normal metallic silver particles and prototypical heavy-fermion superconductors CeCoIn5 and CeRhIn5 at high pressures. In the normal state the Fano line shape of the measured G is well described by a model with two tunneling channels and a large temperature-independent background conductance. In the superconducting state a strongly suppressed Andreev reflection signal is explained by the presence of the background conductance. We report Andreev signal in CeCoIn5 consistent with standard dx2−y2 -wave pairing, assuming an equal mixture of tunneling into [100] and [110] crystallographic interfaces, whereas in CeRhIn5 at 1.8 and 2.0 GPa the signal is described by a dx2−y2 -wave gap with reduced nodal region, i.e., increased slope of the gap opening on the Fermi surface. A possibility is that the shape of the high-pressure Andreev signal is affected by the proximity of a line of quantum critical points that extends from 1.75 to 2.3 GPa, which is not accounted for in our description of the heavy-fermion superconductor.

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Denna post skapades 2014-09-23. Senast ändrad 2015-05-25.
CPL Pubid: 203165


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