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Diamagnetic susceptibility of spin-triplet ferromagnetic superconductors
We calculate the diamagnetic susceptibility in zero external magnetic field
above the phase transition from ferromagnetic phase to phase of coexistence of
ferromagnetic order and unconventional superconductivity. For this aim we use
generalized Ginzburg-Landau free energy of unconventional ferromagnetic
superconductor with spin-triplet electron pairing. A possible application of
the result to some intermetallic compounds is briefly discussed.Comment: 7 pages, 1 figur
Phenomenological description of anisotropy effects in some ferromagnetic superconductors
We study phenomenologically by using the previously derived Landau free
energy, the role of anisotropy in ferromagnetic superconductors UGe2, URhGe,
and UCoGe. The three compounds are separately discussed with the special stress
on UGe2. The main effect comes from the strong uniaxial anisotropy of
magnetization while the anisotropy of Cooper pairs and crystal anisotropy only
slightly change the phase diagram in the vicinity of Curie temperature. The
limitations of this approach are also discussed.Comment: 12 pages, 4 figure
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
Functional renormalization for quantum phase transitions with non-relativistic bosons
Functional renormalization yields a simple unified description of bosons at
zero temperature, in arbitrary space dimension and for complex fields.
We concentrate on nonrelativistic bosons and an action with a linear time
derivative. The ordered phase can be associated with a nonzero density of
(quasi) particles . The behavior of observables and correlation functions in
the ordered phase depends crucially on the momentum , which is
characteristic for a given experiment. For the dilute regime the quantum phase transition is simple, with the same ``mean field''
critical exponents for all and . On the other hand, the dense regime
reveals a rather rich spectrum of features, depending on
and . In this regime one observes for a crossover to a
relativistic action with second time derivatives. This admits order for ,
whereas shows a behavior similar to the low temperature phase of the
classical two-dimensional -models.Comment: 31 pages, new reference
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