1,065 research outputs found
Theory of ferromagnetic superconductors with spin-triplet electron pairing
A general quasi-phenomenological theory that describes phases and phase
transitions of ferromagnetic superconductors with spin-triplet electron Cooper
pairing is presented. The theory is based on extended Ginzburg-Landau expansion
in powers of superconducting and ferromagnetic order parameters. A simple form
for the dependence of theory parameters on the pressure ensures a correct
theoretical outline of the temperature-pressure phase diagram where a stable
phase of coexistence of p-wave superconductivity and itinerant ferromagnetism
appears. This new theory is in an excellent agreement with the experimental
data for intermetallic compounds, for example, UGe2, URhGe, UCoGe, and UIr that
are experimentally proven to be itinerant ferromagnets exhibiting spin-triplet
superconductivity. The mechanism of appearance of superconductivity due to
itinerant ferromagnetism (-trigger effect) is established and demonstrated.
On the basis of the same theory, basic features of quantum phase transitions in
this type of ferromagnetic superconductors are explained in agreement with the
experimental data. The theory allows for a classification of the spin-triplet
ferromagnetic superconductors in two different types: type I and type II. The
classification is based on quantitative criteria, i.e., on simple relations
between theory parameters. Both theory and experiment indicate that the two
types of p-wave ferromagnetic superconductors are well distinguished by
essential differences in their physical properties.Comment: Report at Physics Congress, Sofia, Sept 2013; to appear, in:
Bulg.J.Phys. (2014
Theory of ferromagnetic unconventional superconductors with spin-triplet electron pairing
A general phenomenological theory is presented for the phase behavior of
ferromagnetic superconductors with spin-triplet electron Cooper pairing. The
theory describes in details the temperature-pressure phase diagrams of real
inter-metallic compounds exhibiting the remarkable phenomenon of coexistence of
spontaneous magnetic moment of the itinerant electrons and spin-triplet
superconductivity. The quantum phase transitions which may occur in these
systems are also described. The theory allows for a classification of these
itinerant ferromagnetic superconductors in two types: type I and type II. The
classification is based on quantitative criteria.The comparison of theory and
experiment is performed and outstanding problems are discussed.Comment: 25 pages, 7 figures; CP-ISSP-BAS preprint; a preliminary version of a
review paper; to be submitted for a publicatio
Diamagnetic critical singularity in unconventional ferromagnetic superconductors
The scaling properties of the free energy, the diamagnetic moment, and the
diamagnetic susceptibility above the phase transition from the ferromagnetic
phase to the phase of coexistence of ferromagnetic order and superconductivity
in unconventional ferromagnetic superconductors with spin-triplet (p-wave)
electron paring are considered. The crossover from weak to strong magnetic
induction is described for both quasi-2D (thin films) and 3D (bulk)
superconductors. The singularities of diamagnetic moment and diamagnetic
susceptibility are dumped for large variations of the pressure and, hence, such
singularities could hardly be observed in experiments. The results are obtained
within Gaussian approximation on the basis of general theory of ferromagnetic
superconductors with p-wave electron pairing.Comment: To be published in Bulg. J. Phys (2012
Comment on "Fluctuation-induced first-order transition p-wave superconductors" by Qi Li, D. Belitz, and J. Toner [Phys. Rev. B79, 054514 (2009)]
In this Comment, we show that the paper by Qi Li, D. Belitz and J. Toner,
published in Phys. Rev. B {\bf 79}, 054514 (2009), contains an incomplete
mean-field analysis of a simple model of Ginzburg-Landau type. The latter
contains a stable non-unitary phase, which has not been found in this study and
is missing in the outlined picture of possible stable phases. In this Comment,
the mean field analysis has been corrected, the errors have been explained in
details and relevant topics have been discussed. Shortcomings in the
mean-field-like and renormalization group studies in the mentioned paper have
also been revealed.Comment: accepted in Phys. Rev.
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