About the magnetic fluctuation effect on the phase transition to superconducting state in Al

The free energy and the order parameter profile near the phase transition to the superconducting state in bulk Al samples are calculated within a mean-field-like approximation. The results are compared with those for thin films.Comment: 11 pages, miktex, 2 figure

Thermodynamics of ferromagnetic superconductors with spin-triplet electron pairing

We present a general thermodynamic theory that describes phases and phase transitions of ferromagnetic superconductors with spin-triplet electron Cooper pairing. The theory is based on extended Ginzburg-Landau expansion in powers of superconducting and ferromagnetic order parameters. We propose a simple form for the dependence of theory parameters on the pressure that allows correct theoretical outline of the temperature-pressure phase diagram for which at low temperatures a stable phase of coexistence of p-wave superconductivity and itinerant ferromagnetism appears. We demonstrate that the theory is in an agreement with the experimental data for some intermetallic compounds that are experimentally proven to be itinerant ferromagnetic exhibiting spin-triplet superconductivity. Some basic features of quantum phase transitions in such systems are explained and clarified. We propose to group the spin-triplet ferromagnetic superconductors in two different types of thermodynamic behavior, on the basis of quantitative criterion deduced from the present theory and the analysis of experimental data.Comment: Phys. Rev. B (2009) in PRESS; 14 pages, 1 table, 6 figures, Latex2

Meissner phases in spin-triplet ferromagnetic superconductors

We present new results for the properties of phases and phase transitions in spin-triplet ferromagnetic superconductors. The superconductivity of the mixed phase of coexistence of ferromagnetism and unconventional superconductivity is triggered by the presence of spontaneous magnetization. The mixed phase is stable but the other superconducting phases that usually exist in unconventional superconductors are either unstable or for particular values of the parameters of the theory some of them are metastable at relatively low temperatures in a quite narrow domain of the phase diagram. Phase transitions from the normal phase to the phase of coexistence is of first order while the phase transition from the ferromagnetic phase to the coexistence phase can be either of first or second order depending on the concrete substance. Cooper pair and crystal anisotropies determine a more precise outline of the phase diagram shape and reduce the degeneration of ground states of the system but they do not change drastically phase stability domains and thermodynamic properties of the respective phases. The results are discussed in view of application to metallic ferromagnets as UGe2, ZrZn2, URhGe.Comment: 21 pages, 7 figures; Phys. Rev. B (2005) in pres

Effective spatial dimension of extremal non-dilatonic black p-branes and the description of entropy on the world volume

By investigating the critical behavior appearing at the extremal limit of the non-dilatonic, black p-branes in (d+p) dimensions, we find that some critical exponents related to the critical point obey the scaling laws. From the scaling laws we obtain that the effective spatial dimension of the non-dilatonic black holes and black strings is one, and is p for the non-dilatonic black p-branes. For the dilatonic black holes and black p-branes, the effective dimension will depend on the parameters in theories. Thus, we give an interpretation why the Bekenstein-Hawking entropy may be given a simple world volume interpretation only for the non-dilatonic black p-branes.Comment: 4 pages, RevTex, no figures, to appear in Phys. Rev. Let