R. Afzali

Publications (7)5.09 Total impact

• Article: Dependence of interface conductivity on relevant physical parameters in polarized Fermi mixtures

  N. Ebrahimian, M. Mehrafarin, R. Afzali
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  ABSTRACT: We consider a mass-asymmetric polarized Fermi system in the presence of Hartree-Fock (HF) potentials. We concentrate on the BCS regime with various interaction strengths and numerically obtain the allowed values of the chemical and HF potentials, as well as the mass ratio. The functional dependence of the heat conductivity of the N-SF interface on relevant physical parameters, namely the temperature, the mass ratio, and the interaction strength, is obtained. In particular, we show that the interface conductivity starts to drop with decreasing temperature at the temperature, $T_{\text{m}}$, where the mean kinetic energy of the particles is just sufficient to overcome the SF gap. We obtain $T_{\text{m}}$ as a function of the mass ratio and the interaction strength. The variation of the heat conductivity, at fixed temperature, with the HF potentials and the imbalance chemical potential is also obtained. Finally, because the range of relevant temperatures increases for larger values of the mass ratio, we consider the $^6\text{Li}$-$^{40}\text{K}$ mixture separately by taking the temperature dependence of the pair potential into account.
  05/2012;
• Source

  Available from: ArXiv

  Article: Linear response of heat conductivity of normal-superfluid interface of a polarized Fermi gas to orbital magnetic field

  N. Ebrahimian, M. Mehrafarin, R. Afzali
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  ABSTRACT: Using perturbed Bogoliubov equations, we study the linear response to a weak orbital magnetic field of the heat conductivity of the normal-superfluid interface of a polarized Fermi gas at sufficiently low temperature. We consider the various scattering regions of the BCS regime and analytically obtain the transmission coefficients and the heat conductivity across the interface in an arbitrary weak orbital field. For a definite choice of the field, we consider various values of the scattering length in the BCS range and numerically obtain the allowed values of the average and species-imbalance chemical potentials. Thus, taking Andreev reflection into account, we describe how the heat conductivity is affected by the field and the species imbalance. In particular, we show that the additional heat conductivity due to the orbital field increases with the species imbalance, which is more noticeable at higher temperatures. Our results indicate how the heat conductivity may be controlled, which is relevant to sensitive magnetic field sensors/regulators at the interface.
  10/2011;
• Article: Diffusive thermal conductivity of the A1-phase of superfluid 3He at low temperatures

  R Afzali, N Ebrahimian
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  ABSTRACT: The diffusive thermal conductivity tensor of the A1-phase of superfluid 3He at low temperatures and melting pressure are calculated beyond the s–p approximation, by using the Boltzmann equation approach. The interaction between normal–normal, normal–Bogoliubov and Bogoliubov–Bogoliubov quasiparticles in the collision integrals are considered for important scattering processes such as binary process. At low temperatures, we show that the scattering between Bogoliubov and normal quasiparticles in binary processes plays an important role in the A1-phase, and Bogoliubov–Bogoliubov interaction is ignorable. We show that the two normal and superfluid components take part in elements of the diffusive thermal conductivity tensor differently. We obtain the result that the elements of the diffusive thermal conductivities, Kxx, Kyy and Kzz, are proportional to T−1, and also that the superfluid components of the diffusive thermal conductivity tensor, and , are proportional to T3 and T, respectively.
  Journal of Physics Condensed Matter 06/2005; 17(28):4441. · 2.55 Impact Factor
• Source

  Available from: arxiv.org

  Article: Shear viscosity of superfluid 3He-A_1 at low temperatures

  M. A. Shahzamanian, R. Afzali
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  ABSTRACT: The shear viscosity tensor of the A_1-phase of superfluid 3He is calculated at low temperatures and melting pressure, by using Boltzmann equation approach. The two normal and superfluid components take part in elements of the shear viscosity tensor differently. The interaction between normal and Bogoliubov quasiparticles in the collision integrals is considered in the binary, decay and coalescence processes. We show that the elements of the shear viscosities $\eta_{xy}$, $\eta_{xz}$ and $\eta_{zz}$ are proportional to $(T/T_c)^{-2}$. The constant of proportionality is in nearly good agreement with the experimental results of Roobol et al.
  08/2004;
• Article: Quasiparticle relaxation rate and shear viscosity of superfluid 3He-A_1 at low temperatures

  M. A. Shahzamanian, R. Afzali
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  ABSTRACT: Quasiparticle relaxation rate,$\tau_{p}^{-1}$, and the shear viscosity tensor of the A_1-phase of superfluid 3He are calculated at low temperatures and melting pressure, by using Boltzmann equation approach in momentum space. The collision integral is written in terms of inscattering and outscattering collision integrals. The interaction between normal and Bogoliubov quasiparticles is considered in calculating transition probabilities in the binary, decay and coalescence processes. We obtain that both $\tau_{p\uparrow}^{-1}$ and $\tau_{p\downarrow}^{-1}$ are proportional to $T^2$ >. The shear viscosities $\eta_{xy}$, $\eta_{xz}$ and $\eta_{zz}$ are proportional to $(T/T_c)^{-2}$. The constant of proportionality of the shear viscosity tensor is in nearly good agreement with the experimental results of Roobol et al., and our exact theoretical calculation. Comment: 8 pages, some typos were corrected
  07/2004;
• Article: Shear viscosity of the A1-phase of superfluid 3 He

  M A Shahzamanian, R Afzali
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  ABSTRACT: The scattering processes between the quasiparticles in the spin-up superfluid and the quasiparticles in the spin-down normal fluid are added to the other relevant scattering processes in the Boltzmann collision terms. The Boltzmann equation has been solved exactly for temperatures just below Tc1. The shear viscosity component of the A1-phase drops as C1 (1 − T /Tc1)1/2. The numerical factor C1 is in fairly good agreement with the experiments.
  Journal of Physics Condensed Matter 01/2003; 15(3):367. · 2.55 Impact Factor
• Source

  Available from: arxiv.org

  Article: Shear viscosity of the A_1-phase of superfluid 3He

  M. A. Shahzamanian, R. Afzali
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  ABSTRACT: The scattering processes between the quasiparticles in spin- up superfluid with the quasiparticles in spin-down normal fluid are added to the other relevant scattering processes in the Boltzmann collision terms. The Boltzmann equation has been solved exactly for temperatures just below T_c_1. The shear viscosity component of the A_1- phase drops as C_1(1-T/T_c_1)^(1/2). The numerical factor C_1 is in fairly good agreement with the experiments.
  09/2002;