Lattice vortex

The authors of Ref. [12] reconsidered the problem of magnetic field in quark matter taking into account the rotated electromagnetism . They came to the conclusion that magnetic field can exist in superconducting quark matter in any case, although it does not form a quantized vortex lattice, because it obeys sourceless Maxwell equations and there is no Meissner effect. In our opinion this latter result is incorrect, since the equations for gauge fields were not taken into account and the boundary conditions were not posed correctly. 

Vortex lattice and magnetic order in ErNi2B2C and TmNi2B2C.276... 

Investigations of the normal state magnetoresistance (MR) as well as the Hall effect and the thermal conductivity in the normal and superconducting mixed states give an important information about the electronic structure and the properties of vortex lattice of the investigated materials. 

For LuNi2B2C as well as YNi2B2C, at sufficiently high fields applied parallel to the tetragonal c axis, square vortex lattices as shown in the figs 51a and 52 have been observed (De Wilde et al. 1997 Yethiraj et al. 1997, 1998 Paul et al. 1998 Ghosh and Shrivastiava... 

In addition to the hexagonal-square transition, a reorientation transition of the hexagonal vortex lattice from a state with the diagonal of the rhombic unit cell along [110] direction to [100] direction has been observed for YNi2B2C (Paul et al. 1998). Figure 51b shows that for H applied perpendicular to c the transition to a (nearly) square lattice occurs at a field of about 1 Tesla and at 0.8 Tesla a reorientation transition of the diagonal of the rhombic cell takes place (Sakata et al. 2000). 

The elastic moduli of the vortex lattice around the transition field H j of have been analyzed within the nonlocal London model by Miranovic and Kogan (2001). In particular, the square vortex lattice was found to be soft with respect to shear displacement along the square sides [110] or [110]. 

The symmetry changes of the vortex lattice in borocarbide superconductors affect their pinning properties as was shown for YNi2B2C (Silhanek et al. 2001). For the field orientation // c, the reorientation transition of the vortex lattice mentioned above was found to be associated with a significant kink in the volume pinning force Fp, whereas in the basal plane (for H c) the signature of nonlocal effects is a fourfold periodicity of Fp. 

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,... 

An interesting question is whether the subtle effects of non-locality and, in particular, the hexagonal-square transition of the vortex lattice would be preserved in the superconducting state of magnetic superconductors such as / Ni2B2C with R = Er and Tm. 

FIGURE 51 Vortex lattice in YNi2B2C schematically derived from SANS investigations at 2 K in magnetic fields applied along the c-axis. (a) jlqH = 0.1 T (b) 0.15 T (c) 0.45 T (after Levett et al., 2002). 

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