Hasil untuk "cond-mat"

P. Jönsson, R. Mathieu, W. Wernsdorfer et al.

N. Emery, C. Hérold, S. Cahen et al.

S. Stishov, A. E. Petrova, S. Khasanov et al.

New high resolution data for heat capacity, heat capacity under applied magnetic fields and resistivity of high quality single crystal of MnSi are reported. Striking mirror symmetry between temperature derivative of resistivity and thermal expansion coefficient of MnSi is displayed. Close similarity between variation of the heat capacity and the temperature derivative of resistivity through the phase transition is observed. It is shown that the heat capacity and thermal expansion coefficient of the helical phase are not influenced by moderate magnetic field.

B. Lavenda, J. Dunning-Davies

There is neither motivation nor need to introduce ‘superstatistics.’ The authors attempt to generalize the Boltzmann factor so as to obtain a more general statistics, i.e. , their so-called superstatistics. The do so by performing a Laplace transform on the probability density function (pdf) of an intensive variable, f ( β ), where β is the inverse temperature. The criteria they use for choosing f ( β ) are the following:

E. Babaev

We show that the recent comment by D. Gorokhov, is based on physically obvious errors and misunderstandings of the content of the criticized papers and is readily refuted. We show that 1) In our paper [1] there were considered situations of both strong and weak interband coupling regimes. 2) In the ref [1] it was given a wide range of physical systems with Josephson coupling strength ranging from being very strong to being exactly zero on symmetry grounds. 3) While the ref [1] is not a phenomenological study of $MgB_2$, the moderately strong Josephson coupling results of [1] apply to $MgB_2$: the described in [1] double-core vortices have been recently observed in $MgB_2$.

Y. Fyodorov, G. Akemann

V. Pudalov, M. Gershenson, H. Kojima et al.

We demonstrate that the experimental data on the temperature dependence of the resistivity and conductivity for high-mobility Si-MOS structures, obtained for a wide range of densities (~ 1:7) at intermediate temperatures, agree quantitatively with theory of interaction corrections in the ballistic regime, T\tau >1. Our comparison does not involve any fitting parameters.

R. Mani

We provide an article-extract which points out that a microwave-induced modification in the resistance occurs at relatively "high" magnetic fields where the radiation is incapable of producing inter-Landau level excitations and, therefore, that the microwave radiation must be producing intra Landau level excitations as well.

L. Fisher, Valery A. Yampol

Comment on the paper "Critical State Theory for Nonparallel Flux Line Lattices in Type-II Superconductors" by A. Badia and C. Lopez is presented here.

S. Ganichev, W. Prettl

Spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs) are reviewed. The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas (2DEG). It is shown that in quantum wells belonging to one of the gyrotropic crystal classes a non-equilibrium spin polarization of uniformly distributed electrons causes a directed motion of electron in the plane of the QW. A characteristic feature of this electric current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribution of spin polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to conclude on the in-plane symmetry of QWs. The effect can also be utilized to develop fast detectors to determine the degree of circular polarization of a radiation beam. Furthermore spin photocurrents at infrared excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.

B. Lavenda, J. Dunning-Davies

The derivation of Student's pdf from superstatistics is a mere coincidence due to the choice of the $\chi^2$ distribution for the inverse temperature which is actually the Maxwell distribution for the speed. The difference between the estimator and the variance introduces a fluctuating temperature that is generally different than the temperature of the variance. Fluctuations in the energy of a composite system are transferred to fluctuations in the temperature via Levy's transform. The randomization of the operational parameter leading to a subordinated process requires the same number of degrees of freedom in the directing as in the original process. In place of Student's pdf we find the subordinated process to Maxwell's speed distribution has a Pareto distribution which is interpreted as the density of the length of the random velocity vector.

J.R. Cond

Jaeyoung Sung

Although the analysis in cond-mat/0510270 is correct, this doesn't mean Jarzynski relation holds always for an arbitrary process. There exists a sufficient and necessary condition for Jarzynski relation to hold for an adiabatic parameter switching process. In contradiction to recent assertions, the validity condition of Jarzynski relation for an adiabatic process is not always satisfied.

M. D. Menezes, R. Dickman

In cond-mat/0107371, Mendonca proposes that diffusion can change the universality class of a parity-conserving reaction-diffusion process. In this comment we suggest that this cannot happen, due to symmetry arguments. We also present numerical results from lattice simulations which support these arguments, and mention a previous result supporting this conclusion.

A. Kuklov

It is shown that the interconversion mechanism for the triplet excitons in Cu_2O suggested recently by G.M. Kavoulakis and A. Mysyrowicz in cond-mat/0001438 can be tested by the two-photon direct creation of the triplet excitons.

Z. Maassarani

The authors of cond-mat/9911072 claim to introduce "new representations of the Hecke algebra." These representations are shown to be the XXC models introduced two years ago in solv-int/9712008, and repeatedly studied and referred to in subsequent papers. They are in fact representations of the Temperley-Lieb algebra. Several other remarks are made and mistakes are pointed out.

M.V.Cheremisin

Recently, S.A.Mikhailov et al presented a theoretical study(cond-mat/0407364) concerning the electromagnetic response of a finite-width two-dimensional electron stripe. Surprisingly, in the above manuscript the magnetic field dependence of the magnetoplasmon spectrum(namely Fig.4) reproduces that reported for the first time in our paper(cond-mat/0405176, JETP Lett., 80, August 2004, in press). We believe that the above curious coincidence may result from the authors not to be informed enough.

Johann Kroha, A. Z. U. O. Karlsruhe, H Germany et al.

An inadequate approximation and its consequences as well as an incorrect statement made in cond-mat/0102150v2 are pointed out.