Tunneling current of the strong-coupling superconductor Pb in a parallel magnetic field

Superconducting nanostructures fabricated with the scanning tunnelling microscope

“…[142,143], the phonon frequencies ω L,T are subtracted from the voltage position of the features corresponding to the transverse and longitudinal phonons ǫ L,T , and divided by twice the zero field superconducting gap 2∆ 0 . The data ( fig.14) follow well the calculations of [143], intended to explain the experiments in thin films [142]. The confinement of the superconducting correlations to its minimal size by increasing the magnetic field occurs without specially marked changes in the way the Cooper pairs are formed.…”

“…The data are extracted directly from the position of the corresponding features in the tunneling density of states (ǫL,T ), and plotted normalized to the superconducting gap at each field. The theory developed by[143] (lines) explains the data. From[140].FIG.…”

Proximity effect and strong-coupling superconductivity in nanostructures built with an STM

“…, where ∆ 0 is the zero field order parameter, R is the radius of the cylinder and l H the magnetic length l H = 256Å/ √ H. The peak in the DOS is rounded and the gap and order parameter are reduced with respect to the zero field value [22][23][24][25]. The gap remains finite in a large range of fields, and it is only very close to the critical field (above about 0.95H c ) where gapless superconductivity sets in.…”

“…[23]), and to the theory of Ref. [24] (solid lines). To determine as accurately as possible the voltage position of the phonon modes as a function of the magnetic field, we make the mean value between positive and negative voltages and find ǫL,T , the voltage position of the maximum in the second derivative d 2 I/dV 2 [13].…”

“…2b). We plot (ǫ L,T − ω L,T ), normalized to 2∆ 0 , as a function of the squared magnetic field, normalized to the field for complete destruction of superconductivity (H/H c ) 2 , together with the tunneling spectroscopy measurements in thin films published in [23,24]. The figure shows the variation of the voltage position of the phonon modes as a function of the magnetic field.…”