scholarly journals POINT-CONTACT SPECTROSCOPY OF MAGNESIUM DIBORIDE WITH DIFFERENT COUNTER-ELECTRODES

2003 ◽  
Vol 17 (27n28) ◽  
pp. 1405-1416
Author(s):  
A. I. D'YACHENKO ◽  
V. YU. TARENKOV ◽  
M. A. BELOGOLOVSKII ◽  
V. N. VARYUKHIN ◽  
A. V. ABAL'OSHEV ◽  
...  
Keyword(s):  
Andreev Reflection ◽  
Magnesium Diboride ◽  
Three Dimensional ◽  
Point Contact ◽  
Band Model ◽  
Counter Electrodes ◽  
Break Junctions ◽  
Point Contact Spectroscopy ◽  
Dc Current ◽  
Two Band Model

We report on tunneling and Andreev-reflection conductance spectra of 39 K superconducting magnesium diboride, obtained with Pb and Au counter-electrodes. Two distinct steps at close to 2.7 and 7.1 meV appear in a low-resistance metallic-type Au–MgB 2 junction characteristic, whereas a tunneling-like spectrum measured for the same junction, annealed by the application of DC current, exhibits only a rounded contribution of the larger gap. Junctions with a superconducting lead counter-electrode pressed into a bulk MgB 2 sample reveal two conductance peaks that are interpreted as the result of the formation of a highly-transmitting break junctions inside the magnesium diboride ceramic. Our results strongly support the two-band model with two different gap values on quasi-two-dimensional σ (7.1 meV) and three-dimensional π (2.7 meV) Fermi surface sheets of MgB 2.

Point—contact spectroscopy on BSCCO— and YBCO—break—junctions

1994 ◽  
Vol 194-196 ◽  
pp. 1707-1708 ◽  
Author(s):  
U. Zimmermann ◽  
D. Dikin ◽  
M. Kuhlmann ◽  
H. Lamprecht ◽  
K. Keck ◽  
...  
Keyword(s):  
Point Contact ◽  
Break Junctions ◽  
Point Contact Spectroscopy

Direct determination of the Andreev reflection probability by means of point contact spectroscopy

2000 ◽  
Vol 76 (9) ◽  
pp. 1152-1154 ◽  
Author(s):  
M. Jakob ◽  
H. Stahl ◽  
J. Knoch ◽  
J. Appenzeller ◽  
B. Lengeler ◽  
...  
Keyword(s):  
Andreev Reflection ◽  
Point Contact ◽  
Direct Determination ◽  
Point Contact Spectroscopy ◽  
Reflection Probability

Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy

1994 ◽  
Vol 49 (15) ◽  
pp. 10484-10494 ◽  
Author(s):  
D. R. Heslinga ◽  
S. E. Shafranjuk ◽  
H. van Kempen ◽  
T. M. Klapwijk
Keyword(s):  
Andreev Reflection ◽  
Point Contact ◽  
Point Contact Spectroscopy

scholarly journals Fluctuation conductivity in two-band superconductor SmFeAsO0.8F0.2

2015 ◽  
Vol 33 (3) ◽  
pp. 644-648 ◽  
Author(s):  
I.N. Askerzade ◽  
R. T. Tagiyeva Askerbeyli
Keyword(s):  
Magnetic Field ◽  
Landau Theory ◽  
Three Dimensional ◽  
Band Model ◽  
Ginzburg Landau ◽  
Band Theory ◽  
Fluctuation Conductivity ◽  
Temperature Dependences ◽  
Two Band Model ◽  
Good Agreement

Abstract In this study we have calculated the fluctuation conductivity near critical temperature of SmFeAsO0.8F0.2 superconductor using two-band Ginzburg-Landau theory. It was illustrated that in the absence of external magnetic field, the two-band model reduced to a single effective band theory with modified temperature dependences. The calculations revealed three-dimensional character of fluctuations of conductivity in the new Fe-based superconductor SmFeAsO0.8F0.2. It has been shown that such a model is in good agreement with experimental data for this compound.

scholarly journals Point-contact Andreev reflection spectroscopy on Bi2Se3 single crystals

2016 ◽  
Vol 30 (13) ◽  
pp. 1642002 ◽  
Author(s):  
C. R. Granstrom ◽  
I. Fridman ◽  
H.-C. Lei ◽  
C. Petrovic ◽  
J. Y. T. Wei
Keyword(s):  
Single Crystals ◽  
Andreev Reflection ◽  
Surface Condition ◽  
Three Dimensional ◽  
Point Contact ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Zero Bias ◽  
Zero Bias Conductance

To study how Andreev reflection (AR) occurs between a superconductor and a three-dimensional topological insulator (TI), we use superconducting Nb tips to perform point-contact AR spectroscopy at 4.2 K on as-grown single crystals of Bi2Se3. Scanning tunneling spectroscopy and scanning tunneling microscopy are also used to characterize the superconducting tip and both the doping level and surface condition of the TI sample. The point-contact measurements show clear spectral signatures of AR, as well as a depression of zero-bias conductance with decreasing junction impedance. The latter observation can be attributed to interfacial Rashba spin-orbit coupling, and the presence of bulk bands at the Fermi level in our samples suggests that bulk states of Bi2Se3 are involved in the observed AR.

GAP MEASUREMENTS IN MgB2 BREAK-JUNCTION AND POINT-CONTACT HETEROSTRUCTURES: TEST OF THE TWO-BAND MODELS

2002 ◽  
Vol 16 (11n12) ◽  
pp. 1553-1561 ◽  
Author(s):  
R. S. GONNELLI ◽  
G. A. UMMARINO ◽  
D. DAGHERO ◽  
A. CALZOLARI ◽  
V. A. STEPANOV
Keyword(s):  
Critical Temperature ◽  
Point Contact ◽  
Temperature Evolution ◽  
Band Model ◽  
Break Junction ◽  
Dirty Limit ◽  
Clean Limit ◽  
Two Band Model ◽  
Contact Measurements

We present a series of results concerning the determination of the gap(s) in MgB2 by means of break-junction and point-contact measurements. We were able to observe the small 3D gap predicted by the two-band models for MgB2 in the clean limit as well as the gap in dirty limit. We were also able to follow the temperature evolution of the latter, from 4.2 K up to a reduced critical temperature. We show that all our results can be explained in the framework of the two-band model provided that the existence of a damaged surface in dirty limit proximized by the clean bulk as well as the occurrence of parallel contacts are admitted.

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