30 research outputs found
Frequency and temperature dependence of the anomalous Hall conductivity in a chiral px+ipy superconductor with impurities
We calculate frequency and temperature dependence of the anomalous ac Hall
conductivity induced by impurity scattering in a chiral px+ipy superconductor,
such as Sr2RuO4, with spontaneous time-reversal-symmetry breaking in the
absence of an external magnetic field. We consider two models of disorder,
Gaussian and non-Gaussian, characterized by the second and third moments of the
random impurity potential, respectively. Within both models, we find that the
anomalous Hall conductivity has a finite real value at zero frequency, exhibits
singularities at the threshold of photon absorption across the superconducting
gap, and decays as some power of the high frequency \Omega. The Hall
conductivity increases linearly with the decrease of temperature below the
superconducting transition and saturates at zero temperature. Using our results
for the high-frequency Hall conductivity, we estimate the polar Kerr angle for
light reflection from the material and compare it with the experimental
measurements in Sr2RuO4 by Xia et al., Phys. Rev. Lett. 97, 167002 (2006).Comment: 22 pages, 12 figures
Field-angle resolved specific heat and thermal conductivity in the vortex phase of UPd_2Al_3
The field-angle dependent specific heat and thermal conductivity in the
vortex phase of UPd_2Al_3 is studied using the Doppler shift approximation for
the low energy quasiparticle excitations. We first give a concise presentation
of the calculation procedure of magnetothermal properties with vortex and FS
averages performed numerically. The comparison of calculated field-angle
oscillations and the experimental results obtained previously leads to a strong
reduction of the possible SC candidate states in UPd_2Al_3. The possible SC gap
functions have node lines in hexagonal symmetry planes containing either the
zone center or the AF zone boundary along c. Node lines in non-symmetry planes
can be excluded. We also calculate the field and temperature dependence of
field-angular oscillation amplitudes. We show that the observed nonmonotonic
field dependence and sign reversal of the oscillation amplitude is due to small
deviations from unitary scattering.Comment: 16 pages, 8 figure
Recent developments in unconventional superconductivity theory
The review of recent developments in the unconventional superconductivity
theory is given. In the fist part I consider the physical origin of the Kerr
rotation polarization of light reflected from the surface of superconducting
. Then the comparison of magneto-optical responses in
superconductors with orbital and spin spontaneous magnetization is presented.
The latter result is applied to the estimation of the magneto-optical
properties of neutral superfluids with spontaneous magnetization. The second
part is devoted to the natural optical activity or gyrotropy properties of
noncentrosymmetric metals in their normal and superconducting states. The
temperature behavior of the gyrotropy coefficient is compared with the
temperature behavior of paramagnetic susceptibility determining the noticeable
increase of the paramagnetic limiting field in noncentrosymmetric
superconductors. In the last chapter I describe the order parameter and the
symmetry of superconducting state in the itinerant ferromagnet with
orthorhombic symmetry. Finally the Josephson coupling between two adjacent
ferromagnet superconducting domains is discussed.Comment: 15 page
Methodologies of Analyzing Inter-Regional Income Inequality and Their Applications to Russia
The Flux-Line Lattice in Superconductors
Magnetic flux can penetrate a type-II superconductor in form of Abrikosov
vortices. These tend to arrange in a triangular flux-line lattice (FLL) which
is more or less perturbed by material inhomogeneities that pin the flux lines,
and in high- supercon- ductors (HTSC's) also by thermal fluctuations. Many
properties of the FLL are well described by the phenomenological
Ginzburg-Landau theory or by the electromagnetic London theory, which treats
the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft
mainly because of the large magnetic penetration depth: The shear modulus of
the FLL is thus small and the tilt modulus is dispersive and becomes very small
for short distortion wavelength. This softness of the FLL is enhanced further
by the pronounced anisotropy and layered structure of HTSC's, which strongly
increases the penetration depth for currents along the c-axis of these uniaxial
crystals and may even cause a decoupling of two-dimensional vortex lattices in
the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause
thermally activated depinning of the flux lines or of the 2D pancake vortices
in the layers. Various phase transitions are predicted for the FLL in layered
HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to
interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do
not exist as postscript file