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Together with the spinor Boltzmann equation (SBE) satisfied by conduction electrons, we solve the Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation to study the domain wall (DW) motion driven by the spin-polarized current. The SBE and LLGS equation are coupled together by the spin transfer torque (STT) induced by the s–d exchange interaction between the conduction electrons and the local magnet of DW. Based on the spin diffusion equation derived from SBE, we obtain a generalized STT originated from the inhomogeneity of spin current density, which can be divided into adiabatic and nonadiabatic parts but with somewhat different terms from the previous works. We illustrate this by an example of DW motion in a ferromagnet metal under an external electric field, the spin accumulation, and spin current density of conduction electrons and the DW dynamics are presented. We find that the nonadiabatic STT has a comparable contribution to the total STT within the spin-flip relaxation time, which can play an important role in the nonequilibrium DW dynamics. We also estimate the velocity of DW ∼ 100 m/s when an 10 6 V/m electric field is applied. [ABSTRACT FROM AUTHOR]

The anisotropic antiferromagnetic Ising model on the fractal Sierpiński gasket is intensively studied, and a number of exotic properties are disclosed. The ground state phase diagram in the plane of magnetic field-interaction of the system is obtained. The thermodynamic properties of the three plateau phases are probed by exploring the temperature-dependence of magnetization, specific heat, susceptibility and spin-spin correlations. No phase transitions are observed in this model. In the absence of a magnetic field, the unusual temperature dependence of the spin correlation length is obtained with 0 ≤ J/ J< 1, and an interesting crossover behavior between different phases at J/ J = 1 is unveiled, whose dynamics can be described by the J/ J-dependence of the specific heat, susceptibility and spin correlation functions. The exotic spin-spin correlation patterns that share the same special rotational symmetry as that of the Sierpiński gasket are obtained in both the 1 / 3 plateau disordered phase and the 5/9 plateau partially ordered ferrimagnetic phase. Moreover, a quantum scheme is formulated to study the thermodynamics of the fractal Sierpiński gasket with Heisenberg interactions. We find that the unusual temperature dependence of the correlation length remains intact in a small quantum fluctuation. [ABSTRACT FROM AUTHOR]

We report a theoretical analysis of the phonon thermal conductance, κ( T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ( T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length is slightly varied, κ( T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior of κ( T). [ABSTRACT FROM AUTHOR]

In this paper, we apply Büttiker's gauge invariant, charge conservation, nonlinear transport theory to explore the spin-polarized tunneling of ferromagnet/insulator (semiconductor) single and double junctions. The Green function of spin-polarized tunneling is calculated by the tight-binding approximation method. The energy and the angle (between the molecular field and the vertical axis) dependences of the weakly nonlinear dc transport coefficient and the linear low frequency ac transport coefficient are investigated. The ac tunneling magnetoresistance is also discussed. [ABSTRACT FROM AUTHOR]

Based on the spinor Boltzmann equation, we obtain the continuity equations of charge and spin accumulation in two-dimensional ferromagnets with Rashba or Dresselhaus spin-orbit coupling, in which the spin diffusion equation (the continuity equation of spin accumulation) gives the spin-orbit torques that have an extra term of charge density gradient that is paid little attention in previous studies. Numerical results indicate this term plays an important role in inhomogeneous systems. In order to study the magnetization dynamics of ferromagnets, we solve the Landau-Lifshitz-Gilbert equation together with the spin diffusion equation. Our results indicate that the magnetization in systems with Rashba SOI is easier to be switched by an external electric field than the system with Dresselhaus SOI, and for anisotropic ferromagnets, we study the critical external electric field that manipulate the reversal of magnetization. [ABSTRACT FROM AUTHOR]

The scaling behaviors of entanglement entropy (EE) against dimension cut-off of density matrix renormalization group (DMRG) in an anisotropic Heisenberg model on honeycomb lattice are investigated. In the gapped dimer phase, the entanglement spectrum (ES) exhibits large gaps and the EE shows an unexpected linear scaling before convergence. In contrast in the gapless Néel phase, the ES decays in a much smoother way, and the EE scales logarithmically. Our calculations show that the linear scaling in the dimer phase originates from one dominant Schmidt number plus n (nearly) degenerate Schmidt numbers that are much smaller than the dominant one. The non-trivial entanglement-scaling properties of the dimer and Néel phases could potentially be used for their detections. [ABSTRACT FROM AUTHOR]