scholarly journals The Stratified Superconductivity in Ba0.6K0.4BiO3 Single Crystal: Direct Measurement of Energy Gap between Homo-, and Inhomogeneous States

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
L. N. Zherikhina ◽  
A. M. Tskhovrebov ◽  
L. A. Klinkova ◽  
D. A. Balaev ◽  
S. I. Popkov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fermi Surface ◽  
Single Crystal ◽  
Superconducting State ◽  
Energy Gap ◽  
Electric Transport ◽  
Josephson Tunneling ◽  
Josephson System ◽  
First Time ◽  
Inhomogeneous Superconductor

The existence of space inhomogeneous superconductor insulator state (SISIS) found out earlier in polycrystalline samples of high- TC system Ba0.6K0.4BiO3 (TC≈30 K) is confirmed on Ba0.6K0.4BiO3 single crystal. At T* (T*<TC,T*≈17 K) the transition from the homogeneous superconducting state into the SISIS occurs. SISIS is characterized by the appearance of two gaps on the Fermi surface, semi- and superconducting, which are modulated in space in antiphase, the electric transport between superconducting regions being carried out due to Josephson tunneling. Thus the whole sample becomes a multiple Josephson system. Nonlinear I-V curves are observed on Ba0.6K0.4BiO3 single crystal at temperatures below T*. Dependence of I-V curves on temperature and magnetic field, typical to a Josephson system, was found out. Besides, a step-like peculiarity at the values of voltage of the order of one and two superconducting gaps shows up. These peculiarities are suppressed by magnetic field much earlier than critical current. The new data firstly correlate with the model of SISIS and secondly permit for the first time to determining directly the energy gap between homogeneous and stratified superconductor states.

scholarly journals Two-Fermi-Surface Superconducting State and a Nodald-Wave Energy Gap of the Electron-DopedSm1.85Ce0.15CuO4−δCuprate Superconductor

2011 ◽  
Vol 106 (19) ◽  
Author(s):  
A. F. Santander-Syro ◽  
M. Ikeda ◽  
T. Yoshida ◽  
A. Fujimori ◽  
K. Ishizaka ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Wave Energy ◽  
Superconducting State ◽  
Energy Gap

Magnetotransport phenomena in layered conductors under magnetic breakdown

2017 ◽  
Vol 31 (14) ◽  
pp. 1750114
Author(s):  
O. Galbova ◽  
V. G. Peschansky ◽  
D. I. Stepanenko
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Energy Spectrum ◽  
Hydrostatic Pressure ◽  
Fermi Surface ◽  
Linear Dependence ◽  
Energy Gap ◽  
Electron Energy Spectrum ◽  
External Effects ◽  
Magnetic Breakdown

We study the transport phenomena in layered conductors with rather general electron energy spectrum placed in a high magnetic field [Formula: see text], under conditions when the distance between various sheets of the Fermi surface (FS) may become small under the external effects, such as hydrostatic pressure or impurity atom doping, and electrons can transfer from one sheet of the FS to another due to magnetic breakdown. We calculate the dependence of the in-plane electrical conductivity and magnetoresistance on magnetic field and probability of magnetic breakdown and show that the field-induced quadratic increase of the in-plane resistance in the absence of magnetic breakdown is changed by a linear dependence on [Formula: see text]. With a further reduction of the energy gap between FS sheets, the in-plane resistance is saturated.

Transport Properties of Topological Insulator Bi0.83Sb0.17 Nanowires

2015 ◽  
Vol 1785 ◽  
pp. 1-6
Author(s):  
L.A. Konopko ◽  
A.A. Nikolaeva ◽  
T.E. Huber ◽  
J.P. Ansermet
Keyword(s):  
Magnetic Field ◽  
Single Crystal ◽  
Transport Properties ◽  
Topological Insulator ◽  
Energy Gap ◽  
Oscillation Amplitude ◽  
Glass Capillary ◽  
Wire Axis ◽  
Temperature Dependences ◽  
The Wire

ABSTRACTWe have investigated the transport properties of topological insulator based on single-crystal Bi0.83Sb0.17 nanowires. The single-crystal nanowire samples in the diameter range 200 nm – 1.1 μm were prepared by the high frequency liquid phase casting in a glass capillary using an improved Ulitovsky technique; they were cylindrical single-crystals with (1011) orientation along the wire axis. In this orientation, the wire axis makes an angle of 19.5o with the bisector axis C1 in the bisector-trigonal plane. Bi0.83Sb0.17 is a narrow gap semiconductor with energy gap at L point of Brillouin zone ΔE= 21 meV. In accordance with the measurements of the temperature dependence of the resistivity of the samples resistance increases with decreasing temperature, but at low temperatures decrease in the resistance is observed. This effect, decrease in the resistance, is a clear manifestation of the interesting properties of topological insulators - the presence on its surface of a highly conducting zone. The Arrhenius plot of resistance R in samples with diameter d=1.1 µm and d=200 nm indicates a thermal activation behavior with an activation gap ΔE= 21 and 35 meV, respectively, which proves the presence of the quantum size effect in these samples. We found that in the range of diameter 1100 nm - 200 nm when the diameter decreases the energy gap is growing as 1/d. We have investigated magnetoresistance of Bi0.83Sb0.17 nanowires at various magnetic field orientations. From the temperature dependences of Shubnikov de Haas oscillation amplitude for different orientation of magnetic field we have calculated the cyclotron mass mc and Dingle temperature TD for longitudinal and transverse (B||C3 and B||C2) directions of magnetic fields, which equal 1.96*10-2m0, 9.8 K, 8.5*10-3m0 , 9.4 K and 1.5*10-1m0 , 2.8 K respectively. The observed effects are discussed.

Magnetoacoustic oscillations and the stress dependence of the Fermi surface of tungsten

1976 ◽  
Vol 54 (12) ◽  
pp. 1234-1239 ◽  
Author(s):  
D. J. Stanley ◽  
J. M. Perz ◽  
H. -P. Au
Keyword(s):  
Fermi Surface ◽  
Elastic Constant ◽  
Single Crystal ◽  
Cross Sections ◽  
Single Crystal Sample ◽  
Stress Dependence ◽  
Crystal Sample ◽  
Quantum Oscillations ◽  
Strain Dependence ◽  
First Time

The absolute amplitudes of quantum oscillations in magnetostriction and the elastic constant, c11, have been measured simultaneously, for the first time, in a single crystal sample of tungsten. They are combined to give the strain dependence of the Fermi surface cross sections normal to [100] of the ball and ellipsoid surfaces. Comparison with values measured in another type of uniaxial experiment and with pressure derivatives indicates that the results are consistent, and that the method is feasible, although less convenient than other possible measurements giving the same information.

Induced Torque in Aluminum

1973 ◽  
Vol 51 (16) ◽  
pp. 1786-1793 ◽  
Author(s):  
F. W. Holroyd ◽  
R. J. Douglas ◽  
W. R. Datars
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Fermi Surface ◽  
Single Crystal ◽  
Path Integral ◽  
Rotating Magnetic Field ◽  
Closed Orbits ◽  
High Fields ◽  
Crystallographic Planes ◽  
The Magnetic Field

Torque on single-crystal spheres of aluminum induced by a rotating magnetic field was studied in fields up to 20 kOe at 4.2 K. The magnetic field was rotated in (112), (011), and (001) crystallographic planes. Anisotropy of the induced torque showed minima at [Formula: see text] and [Formula: see text] directions. It was reproducible in different samples and persisted in samples that had been strained by up to 8%. The torque anisotropy existed between 1.2 and 35 K. There was no evidence of open orbits. The induced torque tended towards saturation at high fields, and was attributed to closed orbits. The induced torque determined from a path-integral calculation of the magnetoconductivity, assuming the relaxation time to be isotropic and representing the Fermi surface by a modified single-OPW model which had no open orbits, is in excellent agreement with experiment.

51V NMR Study of a C15 Laves Phase Compound HfV2

2002 ◽  
Vol 57 (6-7) ◽  
pp. 513-517
Author(s):  
Yutaka Kishimoto ◽  
Takashi Ohno
Keyword(s):  
Fermi Surface ◽  
Electronic State ◽  
Density Of States ◽  
Superconducting State ◽  
Transformation Temperature ◽  
Energy Gap ◽  
Laves Phase ◽  
Nmr Study ◽  
Phase Compound ◽  
D Wave

We analyzed the K-x plot in order to investigate the change in the electronic state in the C15 Laves phase compound HfV2 at the lattice transformation temperature TL (~120 K). We could obtain K3d orb X3d orb, and X5d orb + (2/3) XPauli + Xdia, which are consistent with those reported in our previous paper, and discussed the changes in density of states of the V3d and 4s electrons at TL. For the superconducting state we discussed the d wave Anderson-Brinkman-Morel (ABM) type energy gap in which the gap is anisotropic and vanishes at points on the Fermi surface

Pressure Dependence of the Energy Gap Anisotropy in Aluminum

1972 ◽  
Vol 50 (21) ◽  
pp. 2568-2573
Author(s):  
C. R. Leavens ◽  
J. P. Carbotte
Keyword(s):  
Fermi Surface ◽  
Single Crystal ◽  
Pressure Dependence ◽  
Energy Gap ◽  
Superconducting Energy Gap ◽  
Gap Anisotropy ◽  
Pure Single Crystal

We have calculated the superconducting energy gap for a large number of points on the irreducible (1/48)th of the Fermi surface of pure single-crystal aluminum both at zero and finite pressure. It is found that the energy gap anisotropy in aluminum increases with increasing pressure.

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