scholarly journals Evidence for bulk superconductivity in pure bismuth single crystals at ambient pressure

Science ◽  
2016 ◽  
Vol 355 (6320) ◽  
pp. 52-55 ◽  
Author(s):  
Om Prakash ◽  
Anil Kumar ◽  
A. Thamizhavel ◽  
S. Ramakrishnan
Keyword(s):  
Magnetic Field ◽  
Single Crystals ◽  
Normal State ◽  
Carrier Density ◽  
Adiabatic Approximation ◽  
Ambient Pressure ◽  
Theoretical Work ◽  
Critical Magnetic Field ◽  
Bulk Superconductivity ◽  
Pure Bismuth

At ambient pressure, bulk rhombohedral bismuth is a semimetal that remains in the normal state down to at least 10 millikelvin. Superconductivity in bulk bismuth is thought to be unlikely because of the extremely low carrier density. We observed bulk superconductivity in pure bismuth single crystals below 0.53 millikelvin at ambient pressure, with an estimated critical magnetic field of 5.2 microteslas at 0 kelvin. Superconductivity in bismuth cannot be explained by the conventional Bardeen-Cooper-Schrieffer theory because its adiabatic approximation does not hold true for bismuth. Future theoretical work will be needed to understand superconductivity in the nonadiabatic limit in systems with low carrier densities and unusual band structures, such as bismuth.

Out-of-Plane and in-Plane Conduction in Insulating and Strongly Underdoped Cuprates

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3203-3206
Author(s):  
C. C. Almasan ◽  
G. A. Levin ◽  
E. Cimpoiasu ◽  
T. Stein ◽  
D. A. Gajewski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Normal State ◽  
Low Temperatures ◽  
Elementary Step ◽  
Charge Carriers ◽  
Two Dimensional ◽  
Out Of Plane ◽  
Underdoped Cuprates

We report measurements of out-of-plane (ρ c ) and in-plane (ρab) normal-state resistivities of single crystals of insulating PrBa2Cu3O 7-δ and strongly underdoped oxygen deficient YBa2Cu3O 6.41 using a flux transformer method. In the superconducting specimens, the onset of superconductivity was suppressed by a magnetic field of 9 T. We have found that the anisotropy ρc/ρab of these samples increases monotonically at low temperatures with no signs of saturation. The temperature dependence of ρc/ρab for YBa2Cu3O6.41 is well described by ρc/ρab=a +bT-2/3, but over a smaller temperature range than for insulating PrBa2Cu3O 7-δ. Both the absence of saturation of ρc/ρab and its T-2/3 dependence indicate two-dimensional conduction. This means that the average in-plane hopping distance of the localized charge carriers increases with decreasing T according to Mott's [Formula: see text] law, while the elementary step in the c-direction remains T independent, equal to the spacing between the bilayers.

Tri-axial magnetic alignment and rare-earth-dependent tri-axial magnetic anisotropies in REBa2Cu4O8 cuprate superconductors

2013 ◽  
Vol 1654 ◽  
Author(s):  
M. Yamaki ◽  
M. Furuta ◽  
T. Doi ◽  
J. Shimoyama ◽  
S. Horii
Keyword(s):  
Magnetic Field ◽  
Rare Earth ◽  
Magnetic Fields ◽  
Rare Earth Elements ◽  
Single Crystals ◽  
Cuprate Superconductors ◽  
Ambient Pressure ◽  
Axial Orientation ◽  
Magnetic Alignment ◽  
Flux Method

ABSTRACTWe report the growth of single crystals by a flux method in ambient pressure and tri-axial orientation under modulated rotation magnetic fields (MRFs) on REBa2Cu4O8 (RE124, RE; rare earth elements) compounds. RE124 crystals were grown for RE = Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Yb through appropriate choice of source compounds. All the obtained RE124 powders were tri-axially aligned in MRF of 10T, whereas magnetization axes depended on the type of RE. Moreover, it was found from the changes in the degrees of c-axis and inplane orientation that tri-axial magnetic anisotropies of RE124 also depended on the type of RE. This indicates that it appropriate choice of RE is important for the fabrication of tri-axial oriented ceramics in lower magnetic field conditions.

scholarly journals Electron transport and anisotropy of the upper critical magnetic field in Ba0.68K0.32Fe2As2 single crystals

JETP Letters ◽  
2011 ◽  
Vol 93 (1) ◽  
pp. 26-30 ◽  
Author(s):  
V. A. Gasparov ◽  
F. Wolff-Fabris ◽  
D. L. Sun ◽  
C. T. Lin ◽  
J. Wosnitza
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Single Crystals ◽  
Critical Magnetic Field ◽  
Upper Critical Magnetic Field

Characterization of Superconducting PrBa2Cu3Ox

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3242-3250
Author(s):  
Zhigang Zou ◽  
Jinhua Ye ◽  
Kunihiko Oka ◽  
Yoshikazu Nishihara
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystals ◽  
Superconducting State ◽  
Magnetic Measurement ◽  
Stacking Faults ◽  
Critical Magnetic Field ◽  
Oxygen Annealing ◽  
X Ray

The crystal structures of superconducting and nonsuperconducting PrBa2Cu3O x crystals were investigated using a single crystal X-ray precession camera. A large amount of stacking faults were observed in h0l reflections of as-grown supconducting PrBa2Cu3O x single crystals. These diffusing could be relaxed after oxygen annealing. Meanwhile, intensities of 003n (n = 1, 2, 3…) diffraction reflections of annealed crystal were increased significantly, indicating that the structural ordering of 1/3n unit cell was improved. Magnetic measurement exhibited that the superconducting state of PrBa2Cu3O x , is sensitive to magnetic fields and the magnetic fields dependence of the flux melting temperature showed that the sample has the smaller critical magnetic field than YBa2Cu3O x.

Transport Properties of Normal and Quasinormal States of Poor Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3151-3156 ◽  
Author(s):  
Vsevolod Gantmakher
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Low Temperature ◽  
Single Crystals ◽  
Quantum Phase Transition ◽  
Normal State ◽  
Cooper Pairs ◽  
Two Dimensional ◽  
Field State ◽  
The Magnetic Field

There are some doubts whether materials near the superconductor–insulator transition (SIT), either on the insulating side, or with superconductivity suppressed by the magnetic field, behave like an ordinary metal. Two experiments in which this issue is addressed will be reviewed here, namely, transport measurements of two different materials: single crystals YBa2Cu3O 6+x (x ≈ 0.37) — a representative of the HTS family and amorphous InO x where x is the oxygen content which could be changed through moderate-temperature annealing. The low-temperature normal resistivity ρ(T) of YBaCuO crystals on both sides of SIT behaves as usual "bad" metal with conductivity below the Mott's minimum value. The amorphous In-O films behave differently. Those films with superconductivity do not display any characteristic magnetic field which can be interpreted as Bc2. Instead, they give out an example of a quantum phase transition and follow Fisher's model1 for "the field-tuned SIT in disordered two-dimensional superconductors" though they are not precisely two-dimensional and their high-magnetic-field state may not be insulating at all. Apparently, the normal state of InO x films comprises localized Cooper pairs.

scholarly journals Evaluating Superconductors through Current Induced Depairing

2019 ◽  
Vol 4 (2) ◽  
pp. 54
Author(s):  
Milind N. Kunchur
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Normal State ◽  
Critical Magnetic Field ◽  
Point Of View ◽  
Measured Parameter ◽  
Practical Applications ◽  
Upper Critical Magnetic Field ◽  
Equal Importance ◽  
Normal States

The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density j. The critical temperature T c is one of the first parameters that is measured and in a certain way defines the superconductor. From the practical applications point of view, of equal importance is the upper critical magnetic field B c 2 and conventional critical current density j c (above which the system begins to show resistance without entering the normal state). However, a seldom-measured parameter, the depairing current density j d , holds the same fundamental importance as T c and B c 2 , in that it defines a boundary between the superconducting and normal states. A study of j d sheds unique light on other important characteristics of the superconducting state such as the superfluid density and the nature of the normal state below T c , information that can play a key role in better understanding newly-discovered superconducting materials. From a measurement perspective, the extremely high values of j d make it difficult to measure, which is the reason why it is seldom measured. Here, we will review the fundamentals of current-induced depairing and the fast-pulsed current technique that facilitates its measurement and discuss the results of its application to the topological-insulator/chalcogenide interfacial superconducting system.

Low-temperature specific heat and critical magnetic field of α-uranium single crystals

2001 ◽  
Vol 63 (22) ◽  
Author(s):  
J. C. Lashley ◽  
B. E. Lang ◽  
J. Boerio-Goates ◽  
B. F. Woodfield ◽  
G. M. Schmiedeshoff ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Specific Heat ◽  
Single Crystals ◽  
Critical Magnetic Field ◽  
Low Temperature Specific Heat
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