1,646 research outputs found
Strong vortex-antivortex fluctuations in the type II superconducting film
The small size vortex-antivortex pairs proliferation in type II
superconducting film is considered for the wide interval of temperatures below
Tc. The corresponding contribution to free energy is calculated. It is shown
that these fluctuations give the main contribution to the heat capacity of the
film both at low temperatures and in the vicinity of transition
Multiphonon anharmonic decay of a quantum mode
A nonperturbative theory of multiphonon anharmonic transitions between energy
levels of a local mode is presented. It is shown that the rate of transitions
rearranges near the critical level number : at smaller the process
slows down, while at larger it accelerates in time, causing a jump-like
loss of energy followed by the generation of phonon bursts. Depending on
parameters, phonons are emitted in pairs, triplets etc.Comment: submitted to Europhys.Let
Spin crossover: the quantum phase transition induced by high pressure
The relationship is established between the Berry phase and spin crossover in
condensed matter physics induced by high pressure. It is shown that the
geometric phase has topological origin and can be considered as the order
parameter for such transition.Comment: 4 pages, 3 figure
A new class of nodal stationary states in 2D Heisenberg ferromagnet
A new class of nodal topological excitations in a two-dimensional Heisenberg
model is studied. The solutions correspond to a nodal singular point of the
gradient field of the azimuthal angle. An analytical solution found for the
isotropic case. An effect of in-plane exchange anisotropy is studied
numerically. It results in solutions which are analogues of the conventional
out-of-plane solitons in the two-dimensional magnets.Comment: 5 figure
Theory of spin current in chiral helimagnet
We give detailed description of the transport spin current in the chiral
helimagnet. Under the static magnetic field applied perpendicular to the
helical axis, the magnetic kink crystal (chiral soliton lattice) is formed.
Once the kink crystal begins to move under the Galilean boost, the spin-density
accumulation occurs inside each kink and there emerges periodic arrays of the
induced magnetic dipoles carrying the transport spin current. The coherent
motion of the kink crystal dynamically generates the spontaneous
demagnetization field. This mechanism is analogous to the
D\"{o}ring-Becker-Kittel mechanism of the domain wall motion in ferromagnets.
To describe the kink crystal motion, we took account of not only the tangential
-fluctuations but the longitudinal -fluctuations around the
helimagnetic configuration. Based on the collective coordinate method and the
Dirac's canonical formulation for the singular Lagrangian system, we derived
the closed formulae for the mass, spin current and induced magnetic dipole
moment accompanied with the kink crystal motion. To materialize the theoretical
model presented here, symmetry-adapted material synthesis would be required,
where the interplay of crystallographic and magnetic chirality plays a key role
there.Comment: 16 pages, 6 figures, to be published in Phys. Rev.
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