@article{a18bec4b000c4749bafc1adb25ce0caa,
title = "Magnetic field dependence of the tunneling characteristics of proximity effect sandwiches",
abstract = "We have measured the tunneling characteristid on the normal metal side of Ag-Pb and Sn-Pb proximity effect sandwiches. In the bias voltage region associated with the phonon frequencies, the effects due to geometrical resonances, to the superconductors phonons and to the normal metal phonons may be separately observed from their distinct field dependences.",
author = "Chaikin, {P. M.} and Donovan-Vojtovic, {B. F.} and Wilson, {J. A.} and G. Deutscher",
note = "Funding Information: The existence of induced superconductivity in a normal metal N backed by a superconductor S has been established by a number of experiments and is macroscopically largely understood today in terms of the thickness, temperature, and nag— netic field dependence of the superconducting order parameter. A tunneling experiment per— formed on the N side of an N/S sandwich shows an induced energy gap,1 structure in the density of states at ener~iesof the order of the supercon— ductor phono3n{\textquoteright}s anhdo,nonass. shown recently, of the normaWl emesthaolw in this letter that these last ef— fects can be distinguished by applying a magnetic field of suitable strength. It then becomes possible to study separately both the normal metal and the superconductor{\textquoteright}s phonons in proxi— mity effect sandwiches. The former application is of obvious interest when the normal metal is not a superconductor at any attainable tempera— ture.L The latter one may be useful in view of the difficulty of growing good junctions on met— als such as niobium. In addition we are able to test the microscopic theory of the proximity ef— fect. Two different proximity effect mechanisms contribute to the density of states. 1) The Andreev5 scattering from the N—S interface pro— duces electron—hole correlations in the normal metal which result in a finite order parameter and structures at the lead phonon frequencies.2 (This first effect would be present even in the absence of any electron phonon coupling in the normal side.) 2) The observation of the phonon structure from N requires an explanation in terms of a frequency dependent pair potential in the normal metal whose magnitude depends upon the strength of the electron phonon interaction in N and which is most easily observed at the phonom frequencies of the normal metal.3” We show here how these two effects can be separated by apply— ing a magnetic field high enough to quench the induced energy gap and the frequency dependent pair potential in the normal metal, but not the Andreev scattering and its associated structures at the superconductor phonon energies. This Supported by the National Science Foundation Copyright: Copyright 2014 Elsevier B.V., All rights reserved.",
year = "1977",
month = jan,
doi = "10.1016/0038-1098(77)91238-8",
language = "English (US)",
volume = "21",
pages = "331--334",
journal = "Solid State Communications",
issn = "0038-1098",
publisher = "Elsevier Ltd",
number = "4",
}