Phonon spectroscopy of superconducting Nb using point-contact tunneling
- Materials Science Division, Argonne National Laboratory, Argonne, IL (USA)
Tunneling spectroscopy measurements have been made on single crystals of Nb using the point-contact technique with a Au tip. The current-voltage characteristics, {ital I}({ital V}) and {ital dI}/{ital dV}, reproduce the results obtained from conventional, thin-film planar junctions. In the range of 5- to 50-meV bias, the tunneling conductance displays the characteristic structures associated with the phonon density of states for Nb, including a low-energy mode near 10 meV, previously observed only in junctions on the (100) crystal face. These results demonstrate that the point-contact tunneling method can be used to measure the electron-phonon interaction in superconductors with the same degree of sensitivity as found in thin-film tunneling spectroscopy. The high-bias conductance was always an increasing function of voltage, as expected for tunnel-barrier transmission, and never displayed the anomalous decreasing behavior found in low-resistance junctions on high-temperature superconductors (HTS's). We draw some inferences about the effects of heating and discuss them in relation to point-contact tunneling into the HTS materials.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 6174652
- Journal Information:
- Physical Review, B: Condensed Matter; (USA), Vol. 42:13; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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