arXiv subjects
Publications and source records attributed to I. A. Fomin.
Interpretation of the recent experiments of V.V. Dmitriev et. al. on longitudinal resonance in the A-like phase, based on specific properties of "robust" order parameter is proposed.
The argument of Bunkov, L`vov and Volovik contains errors, making the obtained result non-convincing.
Stability of homogeneous precession of spin due to parametric excitation of spin waves is considered as the explanation of the "catastrophic relaxation", that is observed in the superfluid 3He-B. It is shown, that at sufficiently low temperatures homogeneous precession of spin becomes unstable (Suhl instability). At zero temperature increments of growth for all spin wave modes are found. Estimation of the temperature of transition to the unstable state is made.
The order parameter of the quasi-isotropic superfluid A-like phase of 3He is rewritten in a simple form. Effect of anisotropy of magnetic susceptibility of this phase on the frequencies of the spatially uniform oscillations of spin and the spin part of its order parameter are found. Anisotropy of susceptibility has pronounced effect on the low-frequency mode, which is analogous to nutations of the asymmetric top. Possibility of observation of the nutation-like mode is discussed.
As a consequence of a continuous degeneracy of the order parameter of the superfluid 3He the quenched disorder in a form of aerogel gives rise both to a disruption of the orientational long-range order of the condensate and to a significant change of the order parameter itself. There exist a class of quasi-isotropic order parameters which are not sensitive to the disorienting effect of aerogel. While the BW order parameter belongs to this class the ABM does not. Possible candidate for the order parameter of the observed A-like phase is discussed.
The arguments of Volovik are refuted.
Formal derivation of criterion for selection of superfluid phases of 3He in aerogel is presented. At the strength of the derived criterion variation of the order parameter of B-like phase in magnetic field differs from that of B-phase of pure 3He. Possible observable consequences of this difference is discussed.
The argument of V.P.Mineev and M.E.Zhitomirsky is based on unjustified omission of contribution of fluctuations to the free energy of superfluid 3He in aerogel.
Within a phenomenological approach a criterion for a choice of forms of the order parameter of the superfluid phases of 3He in aerogel in a vicinity of the transition temperature is derived. The order parameter of bulk B-phase of 3He meets this criterion and that of the bulk A-phase doesn`t. A class of order parameters of Equal Spin Pairing (ESP) type meeting the derived criterion is discussed. Order parameters belonging to this class are proposed as candidates for the observed A-like superfluid phase of liquid 3He in aerogel. Effect of magnetic field on the order parameters of this class is considered.
Within a phenomenological approach possible forms of the order parameter of the superfluid phases of 3He in a vicinity of the transition temperature are discussed. Effect of aerogel is described by a random tensor field interacting with the orbital part of the order parameter. With respect to their interaction with the random tensor field a group of "robust" order parameters which can maintain long-range order in a presence of the random field is specified. Robust order parameters, corresponding to Equal Spin Pairing (ESP) states are found and proposed as candidates for the observed A-like superfluid phase of liquid 3He in aerogel.
Phenomenological criterion of a choice of the order parameter for superfluid phases of $^3$He in aerogel in a near vicinity of the transition temperature is formulated. Except for the B-phase this criterion is met by the order parameter of axiplanar phase for a special choice of its parameters. It is proposed as a limiting at $T\to T_c$ form of the order parameter for the observed A-like phase.
For the UGe$_2$ ferromagnetic superconductor the forms of the order parameter admitted by the crystal symmetry within the strong spin-orbit coupling scheme are written down. For each of the two possible phases existence of gap nodes required by symmetry is discussed and the nodes are found. Some consequences of presence of the nodes, which may be useful for experimental identification of the phases are discussed as well.
We discuss a model based on a field-induced mixture of two odd-parity irreducible representations to explain the unusual features of Hc2(T) in the heavy fermion compound UBe13. We compare its predictions with recent pressure measurements as well as with the most prominent theoretical models which have been proposed up to now.