THEORY OF POINT CONTACT SPECTRA FOR SYSTEM METAL TIP-SUPERCONDUCTOR WITH INTERNAL JOSEPHSON JUNCTION

1989 ◽  
Vol 03 (10) ◽  
pp. 789-794 ◽  
Author(s):  
M. KUPKA ◽  
O. HUDÁK
Keyword(s):  
Josephson Junction ◽  
Energy Gap ◽  
Point Contact ◽  
Model System ◽  
Point Contacts ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Metal Tip ◽  
Contact Metal

We report on the calculations of current-voltage characteristics and dynamical resistivity for a model system (series connected point contact metal — superconductor and Josephson junction of the S-N-S type) as a function of applied voltage. Calculated shape of dV/dI as a function of V shows some qualitative agreement with measured curves on real low-resistivity point contacts of the type metal tip – ceramic superconductor (LaBaCuO, YBaCuO). Method for determination of the energy gap is proposed.

Point-contact spectroscopy probing the NbSe3 CDW gap in different crystallographic orientations

2002 ◽  
Vol 12 (9) ◽  
pp. 119-122
Author(s):  
A. A. Sinchenko ◽  
P. Monceau
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Energy Gap ◽  
Point Contact ◽  
Point Contacts ◽  
Energy Gaps ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Crystallographic Orientations

We have measured the differential current-voltage characteristics of normal metal-NbSe3 direct point contacts (without insulating barrier) formed along different crystallographic orientations under applied magnetic field with different orientations. At low temperature two energy gaps, $\Delta_{p1}$ and $\Delta_{p2}$, corresponding to the high and the low-temperature CDW were observed simultaneously as a singulanty of the excess resistance which is attributed to an analog of Andreev reflection, in which the incident electron reflects on the Peierls energy gap barriers with its charge unchanged. An applied magnetic field up to 8.5 T does not lead to a change in the density of states and in the Peierls energy gaps, suggesting that the large magnetoresistance observed in NbSe3 might not result from the change in the CDW order parameter with magnetic field but rather from the increase of scattering of non-condensed to CDW carriers.

Electronic Transport through Conical Nanosized GaAs Pillars

2015 ◽  
Vol 1735 ◽  
Author(s):  
Thorben Bartsch ◽  
Christian Heyn ◽  
Wolfgang Hansen
Keyword(s):  
Electronic Transport ◽  
Three Dimensional ◽  
Electronic States ◽  
Quantum Point Contacts ◽  
Point Contacts ◽  
Quantum Size ◽  
Current Voltage ◽  
Quantum Point ◽  
Current Voltage Characteristics ◽  
Lattice Matched

ABSTRACTWe study the electronic transport through epitaxial GaAs nanopillars that are only 16 nm long, with diameters of about 100 nm at the upper and 40 nm at the lower end. The pillars can be considered to be very short conical nanowires embedded in AlGaAs. They represent quantum point contacts between two perfectly lattice matched three-dimensional GaAs charge reservoirs. Distinctive asymmetries are found in the current-voltage characteristics. We associate them with the conical shape of the pillars. Although contact reservoirs and pillars are made from the same material, the transport through the pillars is dominated by tunneling across shallow barriers. This is explained by the quantum size effect on the electronic states within the pillars.

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