Other Condensed Matter
Defects are believed to play a fundamental role in the supersolid state of 4He. We have studied solid 4He in two dimensions (2D) as function of the number of vacancies n_v, up to 30, inserted in the initial configuration at rho = 0.0765…
We consider a homogeneous non-ideal Bose gas at nonzero temperature in equilibrium below the critical temperature $T_C$ in the framework of finite temperature field theory. An algorithm is described in which a manageable subset of diagrams…
We explore the possibility that the fast and exotic negative ions in superfluid helium are electrons bound to quantized vortex structures, the simplest being a ring. In the states we consider, the electron energy is only slightly below the…
Kinetic energies of a system of $^4$He are investigated at zero temperature. The multi-weight extension to the diffusion Monte Carlo method is used to implement the Feynman-Hellmann theorem in an effective way. This method allows the…
Using the general approach of Lax for multiple scattering of waves a 2x2 covariant expression for the reflectivity of polarized slow neutrons of a magnetic layer structure of arbitrary complexity is given including polarization effects of…
General expressions of the electron yield in (^{57})Fe integral conversion electron M\"ossbauer spectroscopy were derived depending on the angle of incidence of the (\gamma)-rays, on the source polarization and on the isotopic abundance of…
Theoretical description of off-specular grazing-incidence nuclear resonant scattering of synchrotron radiation (Synchrotron M\"{o}ssbauer Reflectometry, SMR) is presented. The recently developed SMR, similarly to polarized neutron…
We report on the experimental investigation of the response of a three-dimensional Bose-Einstein condensate (BEC) in the presence of a one-dimensional (1D) optical lattice. By means of Bragg spectroscopy we probe the band structure of the…
We investigate the one-dimensional expansion of a Bose-Einstein condensate in an optical guide in the presence of a random potential created with optical speckles. With the speckle the expansion of the condensate is strongly inhibited. A…
We investigate the localization properties of a one-dimensional bichromatic optical lattice in the tight binding regime, by discussing how exponentially localized states emerge upon changing the degree of commensurability. We also review…
Ginzburg-Landau model with two order parameters appears in many condensed-matter problems. However, even for scalar order parameters, the most general U(1)-symmetric Landau potential with all quadratic and quartic terms contains 13…
We explore the formation of Wigner crystals for charged particles on a toroidal helix. Focusing on certain commensurate cases we show that the ground state undergoes a pitchfork bifurcation from the totally symmetric polygonic to a…
We propose a simple gradient-dependent bound for the exchange-correlation energy (sLL), based on the recent non-local bound derived by Lewin and Lieb. We show that sLL is equivalent to the original Lieb-Oxford bound in rapidly-varying…
The work is devoted to obtaining the 1D bipolaron functional by Holstein method for the continuum approximation. We analyzed the effect of electron correlations associated with the direct dependence of the wave function of the electron…
A computer simulation of the formation of photoexcited electrons in water is performed within the framework of a dynamic model. The obtained results are discussed in comparison with experimental data and theoretical estimates.
The onset of turbulent flow around an oscillating sphere in superfluid $^4$He is known to occur at a critical velocity $v_c \sim \sqrt{\kappa\omega}$ where $\kappa$ is the circulation quantum and $\omega$ is the oscillation frequency. But…
Kelvin waves are expected to play an essential role in the energy dissipation for quantized vortices. However, the identification of these helical distortions is not straightforward, especially in case of vortex tangle. Here we review…
We propose a new approach to calculate van der Waals forces between nanoparticles where the van der Waals energy can be reduced to the energy of elementary surface plasmon oscillations in nanoparticles. The general theory is applied to…
We study the uniform electron gas with a gap model in the context of density functional theory. Based on this analysis, we construct two local gap models that realize generalized gradient approximation (GGA) correlation functionals…
We obtain the reflection coefficients from a graphene sheet deposited on a material substrate under a condition that graphene is described by the hydrodynamic model. Using these coefficients, the gradient of the Casimir force in the…