Superconducting carrier

The re arch in catalysis is still one of the driving forces for interface science. One can certainly add to the topics of interface physics the whole new field of interface problems that is about to spring out of the new high Tc superconducting ceramics, i.e. the fundamental problem of the matching of the superconducting carriers wave-functions with the normal state metal or semiconductor electron states, the super-conductor-superconductor interfaces and so on, as well as the wide open discovery field for devices and applications. 

The second difference between the nickel and copper compounds is that La2Cu04 is a superconductor, being the first of the Cu02 layer compounds in which superconductivity was observed. The lattice-induced strain is a necessary condition for superconductivity since it stabilizes the higher oxidation state needed to provide the superconducting carriers as discussed in Section 13.3.2. 

Keywords SQUID, magnetic microscope, magnetic record, superconducting carrier. 

Scan pictures of some TO s and the possibility of magnetic recording on superconducting carriers... 

A superconductor exhibits perfect conductivity (See Section 7.2) and the Meissner effect (See Section 7.3) below some critical temperature, Tc. The transition from a normal conductor to a superconductor is a second-order, phase-transition which is also well-described by mean-field theory. Note that the mean-field condensation is not a Bose condensation nor does it require and energy gap. The mean-field theory is combined with London-Ginzburg-Landau theory through the concentration of superconducting carriers as follows ... 

Here q is the charge, ns(t) is the concentration and t is the mass of the superconducting carriers. The time-derivative of the current density is... 

CUO2 layers appear in all cuprate superconductors and appear to be a necessary but not sufficient condition for high temperature superconduction. The La2SrCu20g 2 compound has CUO2 layers but does not superconduct. Experiments also indicate that T is proportional to the carrier density in the CUO2 layer but not to the volume carrier density, which is further evidence that the YBa2Cu202 is a two-dimensional superconductor. 

In BajCgQ the band is completely filled. Higher doping levels are reached in the superconductors CajCgQ and Ba5C5Q. In these compounds, the band is also occupied with charge carriers, as shown by the valence band spectra [131, 138]. Therefore, their superconductivity is associated with the band. 

The opening of a band gap at in the superconducting state can also be interpreted within this framework. The charge carriers of a superconducting state are not individual electrons as in the normal metallic state but electrons coupled in pairs, the so-called Cooper pairs, having opposite wave vectors. Hence, Cooper pairs are described by product functions (p k)(p —k)). Following the discussion given above. 

Superlattices result from the periodic infinite repetition of heterostructures. MBE-grown superlattices of III-V semiconductors exhibit sharp interfaces and high carrier mobilities of the resulting 2D carrier gas at low temperature (Ando et al, 1982). To date no superconductivity has been found for such engineered solids, although some expectations were raised in 2000 after some reports on the obten-tion of superconductivity in semiconductor/insulator interfaces by field-induced... 

Komatsu T, Kojima N, Saito G (1997) Ambient-pressure superconductivity of k -(BEDT-TTF)2Cu2(CN)3 realized by a carrier-doping into a Mott-insulating state. Synth Met 85 1519-1520... 

Thin films of an amorphous-composite In/InO, which contain a metal-dielectric interface, have been studied (12)(13) and found to superconduct when the electron carrier density reaches a value of approximately 1020cm-3. This system, having a Tc of 2.5 to 3.2 K, has been described as exhibiting "interface-dominated superconductivity". 

In conclusion, electron microscopy techniques reveal considerable evidence for variability in composition and defect structures, such as cation and anion vacancies, extended defects, substitutional ions and oxygen interstitials these are common to all of the high temperature superconducting oxides. These defects play an important role in controlling the carrier concentrations and therefore the... 

The transport of heat in metallic materials depends on both electronic transport and lattice vibrations, phonon transport. A decrease in thermal conductivity at the transition temperature is identified with the reduced number of charge carriers as the superconducting electrons do not carry thermal energy. The specific heat and thermal conductivity data are important to determine the contribution of charge carriers to the superconductivity. The interpretation of the linear dependence of the specific heat data on temperature in terms of defects of the material suggests care in interpreting the thermal conductivity results to be described. 

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