Vortex phases

In addition to the vortex lattice occupying the main part of the H-T-phase diagram of borocarbide superconductors, several other vortex phases have been identified in the nonmagnetic borocarbides. Mun et al. (1996) found, by transport measurements on YNi2B2C,... 

For the phase determination the same ECMWF analyses were used. Maps of EPV with temperature isolines were drawn. The classification of the vortex phase was based on the occurrence and shape of the EPV region characterising the inner vortex as well as the occurrence of the lowest temperatures. 

Specific heat and magnetotransport in the vortex phase a genuine angular resolved method... 

The field angle dependence of specific heat and thermal transport in the vortex phase have revolutionized the investigation of superconducting gap structure in nodal superconductors. Many ambiguities from the previous methods which have persisted over years have been resolved in a short time. This method certainly has enormous potential, it remains to be seen whether it can also be tried for other quantities, e.g., ultrasonic attenuation in the vortex phase as function of magnetic field direction. 

A more indirect but more versatile method consists in looking for signatures of the gap nodes in the d-density wave states. For low temperatures T A the nodal regions dominate thermodynamics and transport properties. Specific heat and thermal conductivity is equivalent to that of d-SC which have been discussed before. Susceptibility and frequency dependent electrical conductivity however are characteristic for the d-density wave states. Of course there is no vortex phase and the Doppler shift method cannot be applied. 

With the possibihties d = x,y,z due to the AF orthorhombic symmetry. These gap functions have all an equatorial node line at = 0. Confirmation of the node structure has to await the results of angle resolved magnetotransport or specific heat measurements in the vortex phase and for a confirmation of the spin state the Knight shift measurements on high quality single... 

As discussed in sect. 2 the observation of the dHvA effect far in the vortex phase B < Bc2) is a sure signature of nodal superconductivity. Although oscillations of the three Fermi surface sheets in URu2Si2 have been seen below Bc2 (Ohkuni et al., 1999) the amplitude falls of quite rapidly with B, especially for field along c. Therefore, these experiments are not able to confirm the existence of nodes in A (k). 

Thermal conductivity in the vortex phase and multiphase superconductivity in PrOs4Sbi2... 

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