Phase diagram of superfluid <Superscript>3</Superscript>He in “nematically ordered” aerogel

Results of experiments with liquid ³He immersed in a new type of aerogel are described. This aerogel consists of Al₂O₃ · H₂O strands which are nearly parallel to each other, so we call it as a “nematically ordered” aerogel. At all used pressures a superfluid transition was observed and a superfluid phase diagram was measured. Possible structures of the observed superfluid phases are discussed.     

Distorted axi-planar superfluid phase of 3He in the “nematically ordered” aerogel

Stimulated by the results of NMR experiments with superfluid ³He in “nematically ordered” aerogel [R. Sh. Askhadullin, V. V. Dmitriev, D. A. Krasnikhin, et al., JETP Lett. 95, 326 (2012)] we report on the results of phenomenological analysis of stability of different phases of superfluid ³He subjected to a strong homogeneous uniaxial anisotropy. On a basis of this analysis we suggest a form of the order parameter for the new ESP2 phase observed in the quoted experiments. In the weak coupling limit the suggested order parameter approaches that of the axi-planar phase. We discuss a possible experimental check of the proposed identification of the new phase.     

Piston-effect-induced thermal oscillations at the Rayleigh-Bénard threshold in supercritical 3He

We perform a Navier-Stokes numerical simulation of the transient Rayleigh-Bénard convection onset in nearly supercritical 3He in the exact conditions in experiments performed by Kogan, Murphy, and Meyer [Phys. Rev. Lett. 82, 4635 (1999)]Phys. Rev. E 63, 056310 (2001)]]. We find an interpretation of the observed unexpected temperature oscillations at the convection onset in terms of the piston effect. This is our first result towards the exploration of the whole instability diagram as recently mapped in those experiments.     

Superconducting weak links in YBa2Cu3O7−σ an AC magnetic susceptibility study

AC magnetic susceptibility, χ' and χ″, and ac resistivity, ϱ, of two different samples of superconducting YBa₂Cu₃O_7-σ have been measured. The results show a strong non-linear behaviour and are very sensitive to the exciting amplitudes. From the analysis of the data and comparison with appropriate models and other superconducting compounds, evidence for the existence of weak superconducting links is inferred. Finally, the utility of ac χ measurements for detection of different superconducting phases is made evident.     

Motion of vortex lines and mutual friction in superfluid4He nearT λ

The motion of a single vortex line in superfluid⁴He nearT is studied within modelF. The linear response of the vortex-line velocityv _L to a homogeneous counterflowv _s –v _n is calculated up to lowest order of renormalized perturbation theory. The critical temperature dependence is taken into account via the renormalizationgroup theory. Non-asymptotic critical effects are found to be important. The results are generalized to describe collective vortex motion and mutual friction in rotating superfluid⁴He. The phenomenological mutual-friction coefficientsB andB of Hall and Vinen are determined without adjustment of parameters. ForB quantitative agreement with experiments nearT is found whereas forB the agreement is only semiquantiative.     

Stability of the scalar potential and symmetry breaking in the economical 3-3-1 model

A detailed study of the criteria for stability of the scalar potential and the proper electroweak symmetry breaking pattern in the economical 3-3-1 model, is presented. For the analysis we use and improve a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. A new theorem related to the stability of the potential is stated. As a consequence of this study, the consistency of the economical 3-3-1 model emerges.     

Quantum Phase Transition Like Phenomenon in a Two-Qubit Yang-Baxter System

The quantum phase transition for the “q-deformed” Yang-baxter Hamiltonian has been discussed. The calculation shows when the deformed parameter q approaches 1, there exists a quantum critical point for spectral parameter θ. In this Yang-Baxter system, quantum entanglement and the geometric phase can characterize quantum phase transition.     

Geometric Phase in a Time-Dependent System with Laguerre Polynomial State

By using of the invariant theory, we have studied the geometric phase in a time-dependent system with Laguerre polynomial state, the dynamical and geometric phases are given, respectively. The Aharonov-Anandan phase is also obtained under the cyclical evolution.     

Searches for Lorentz violation in 3He/129Xe clock comparison experiments

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized ³He or ¹²⁹Xe samples with a SQUID as magnetic flux detector. Characteristic spin precession times $T_2^\ast$ of up to 115 h were measured in low magnetic fields (about 1 μT) and in the regime of motional narrowing. With the detection of the free precession of co-located ³He/¹²⁹Xe nuclear spins (clock comparison), the device can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference, i.e., Δω?=?ω _He ???γ _He /γ _Xe ·ω _Xe . We report on searches for Lorentz violating signatures by monitoring the Larmor frequencies of co-located ³He/¹²⁹Xe spin samples as the laboratory reference frame rotates with respect to distant stars (sidereal modulation).     

Geometric Phase of Quantum Dots in the Time-Dependent Isotropic Magnetic Field

By using of the invariant theory, we have studied the geometric phase of quantum dots in the time-dependent isotropic magnetic field, the dynamical and geometric phases are given, respectively.     

Phase transitions in a holographic s $$$$ p model with back-reaction

In a previous paper (Nie et al. in JHEP 1311:087, arXiv:1309.2204 [hep-th], 2013), we presented a holographic s \(+\) p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. We also study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back-reaction. The model shows a rich phase structure and various condensate behaviors such as the “n-type” and “u-type” ones, which are also known as reentrant phase transitions in condensed matter physics. The phase transitions to the p-wave phase or s \(+\) p coexisting phase become first order in strong back-reaction cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s \(+\) p solution can also play an important role. The phase diagrams of this model are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back-reaction parameter, which show that the region for the s \(+\) p coexisting phase is enlarged with a small or medium back-reaction parameter but is reduced in the strong back-reaction cases.     

Geometric Phase in a Time-Dependent k-Boson and Fermi System

By using the Lewis–Riesenfeld invariant theory, the geometric phase in a time-dependent k-Boson and Fermi system has been studied. It is found that the geometric phase has nothing to do with the field frequency and the coupling coefficient between the Boson and Fermion.     

Pressure-Induced Phase Transition in BaTiO3 Nanocrystals

The crystal structure and electric properties of BaTiO3 nanocrystals are studied by in situ high-pressure synchrotron radiation x-ray powder diffraction. The phase transition takes place not only in the samples of BaTiO3 nanocrystals that are tetragonal phase with grain sizes more than 100nm, but also in the samples of BaTiO3 nanocrystals that are cubic phase with grain sizes less than 100nm. The pressures of phase transition are found to increase with decrease of the grain size from about 4 to 10GPa for crystallites ranging from 200 to 10nm in radius. The bulk moduli are calculated according to Birch-Murnaghan state equation before and after the phase transition.     

Semisuperfluidity of 3He in aerogel?

According to hydrodynamic, acoustic, and NMR studies the superfluid transition temperature of 3He in aerogel ( T(a)(c)) is significantly suppressed with respect to that of bulk 3He. We have found in the range of temperatures between T(c) and T(a)(c) a large and unexpected NMR satellite line attributable to the liquid inside the aerogel. We propose that this anomalous behavior of liquid 3He corresponds to a new type of superfluid ordering related to magnetic and possibly orbital coherence.     

Master Equation in Phase Space for a Spin in an Arbitrarily Directed Uniform External Field

The time evolution equation for the probability density function of spin orientations in the phase space representation of the polar and azimuthal angles is derived for the nonaxially symmetric problem of a quantum paramagnet subjected to a uniform magnetic field of arbitrary direction. This is accomplished by first rotating the coordinate system into one in which the polar axis is collinear with the field vector, then writing the reduced density matrix equation in the new coordinate system as an explicit inverse Wigner-Stratonovich transformation so that the phase space master equation may be derived just as in the axially symmetric case [Yu.P. Kalmykov et al., J. Stat. Phys. 131:969, 2008]. The properties of this equation, resembling the corresponding Fokker-Planck equation, are investigated. In particular, in the large spin limit, S→∞, the master equation becomes the classical Fokker-Planck equation describing the magnetization dynamics of a classical paramagnet in an arbitrarily directed uniform external field.     

Analyzing Power of 3He(n, n)3He Between 1.60 and 5.54 MeV

We report the measurements of the analyzing power A _y (θ) of n-³He elastic scattering with unprecedented accuracy and angular coverage at five incident neutron energies between 1.60 and 5.54 MeV. To this end, we employed the polarization-transfer reactions ³H(p, n)³He and ²H(d, n)³He at 0° for neutron generation and a recently developed high-pressure ³He gas scintillator as an active target, enabling neutron-time-of-flight and ³He recoil-energy determinations. We obtained simultaneously the neutron polarization with a ⁴He-based polarimeter, capitalizing on the well-known n-⁴He A _y (θ). Our n-³He A _y (θ) data are compared to rigorous four-nucleon calculations using high-precision nucleon–nucleon potential models. The agreement between data and calculations is fair at the lower energies and becomes less satisfactory with increasing neutron energy. However, in comparison to the pure isotriplet p-³He system in the same energy region, the agreement between measured and calculated A _y is much better for the mixed (isotriplet and isosinglet) n-³He system, indicating large and somewhat counterintuitive isospin effects. We note that the incorporation of a Δ-mediated three-nucleon force in calculations of n-³He scattering was found to affect A _y (θ) negligibly, suggesting the need for the reconsideration of fundamental interactions in resolving the four-nucleon analyzing power puzzle first established about a decade ago in p-³He scattering.     

Geometric Phase of Anisotropic Quantum Dots in the Presence of Time-Dependent Magnetic Field

By using of the invariant theory, we have studied the geometric phase of anisotropic quantum dots in the presence of time-dependent magnetic field. The Aharonov-Anandan phase is also obtained under the cyclical evolution.     

Phase Separation in Random Cluster Models III: Circuit Regularity

We study the droplet that results from conditioning the subcritical Fortuin-Kasteleyn random cluster model on the presence of an open circuit Γ encircling the origin and enclosing an area of at least (or exactly) n ². In this paper, we prove that the resulting circuit is highly regular: we define a notion of a regeneration site in such a way that, for any such site v∈Γ, the circuit Γ cuts through the radial line segment through v only at v. We show that, provided that the conditioned circuit is centred at the origin in a natural sense, the set of regeneration sites reaches into all parts of the circuit, with maximal distance from one such site to the next being at most logarithmic in n with high probability. The result provides a flexible control on the conditioned circuit that permits the use of surgical techniques to bound its fluctuations, and, as such, it plays a crucial role in the derivation of bounds on the local fluctuation of the circuit carried out in Hammond (, 2009; , 2009).