924 research outputs found
Symmetry of the order parameter in superconducting ZrZn_2
We apply symmetry considerations to study the possible superconducting order
parameters in ferromagnetic ZrZn_2. We predict that the presence and the
location of the superconducting gap nodes depend on the direction of
magnetization M. In particular, if M is directed along the z axis, then the
order parameter should always have zeros. We also discuss how to determine the
gap symmetry in ZrZn_2 using ultrasound attenuation measurements.Comment: 6 pages, submitted to PRB; some corrections and discussion adde
Symmetry Properties on Magnetization in the Hubbard Model at Finite Temperatures
By making use of some symmetry properties of the relevant Hamiltonian, two
fundamental relations between the ferromagnetic magnetization and a spin
correlation function are derived for the -dimensional Hubbard model
at finite temperatures. These can be viewed as a kind of Ward-Takahashi
identities. The properties of the magnetization as a function of the applied
field are discussed. The results thus obtained hold true for both repulsive and
attractive on-site Coulomb interactions, and for arbitrary electron fillings.Comment: Latex file, no figur
Magnetic-interference patterns in Josephson junctions with d+is symmetry
The magnetic interference pattern and the spontaneous flux in unconventional
Josephson junctions of superconductors with d+is symmetry are calculated for
different reduced junction lengths and the relative factor of the d and s wave
components. This is a time reversal broken symmetry state. We study the
stability of the fractional vortex and antivortex which are spontaneously
formed and examine their evolution as we change the length and the relative
factor of d and s wave components. The asymmetry in the field modulated
diffraction pattern exists for lengths as long as L=10\lambda_J.Comment: 8 pages, 6 eps files, submitted to PR
Localized surface states in HTSC: Alternative mechanism of zero-bias conductance peaks
It is shown that the quasiparticle states localized in the vicinity of
surface imperfections of atomic size can be responsible for the zero-bias
tunneling conductance peaks in high-Tc superconductors. The contribution from
these states can be easily separated from other mechanisms using their
qualitatively different response on an external magnetic field.Comment: REVTeX, 4 pages, 2 figs; to be published in PR
Influence of impurity scattering on tunneling conductance in normal metal- d -wave superconductor junctions
Tunneling conductance spectra between a normal metal / d-wave superconductor
junction under the presence of bulk impurities in the superconductor are
studied. The quasiclassical theory has been applied to calculate the spatial
variation of the pair potential and the effect of impurity scattering has been
introduced by t-matrix approximation. The magnitude of a subdominant s-wave
component at the interface is shown to robust against the impurity scattering
while that for a subdominant -wave component is largely suppressed with
the increase of the impurity scattering rate. The zero-bias conductance peak
due to the zero-energy Andreev bound states is significantly broadened for the
case of Born limit impurity compared with that of unitary limit impurity.Comment: 14 pages, 5 figure
Possible symmetries of the superconducting order parameter in a hexagonal ferromagnet
We study the order parameter symmetry in a hexagonal crystal with co-existing
superconductivity and ferromagnetism. An experimental example is provided by
carbon-based materials, such as graphite-sulfur composites, in which an
evidence of such co-existence has been recently discovered. The presence of a
non-zero magnetization in the normal phase brings about considerable changes in
the symmetry classification of superconducting states, compared to the
non-magnetic case.Comment: 4 pages, REVTe
Interactions between subunits of Saccharomyces cerevisiae RNase MRP support a conserved eukaryotic RNase P/MRP architecture
Ribonuclease MRP is an endonuclease, related to RNase P, which functions in eukaryotic pre-rRNA processing. In Saccharomyces cerevisiae, RNase MRP comprises an RNA subunit and ten proteins. To improve our understanding of subunit roles and enzyme architecture, we have examined protein-protein and protein–RNA interactions in vitro, complementing existing yeast two-hybrid data. In total, 31 direct protein–protein interactions were identified, each protein interacting with at least three others. Furthermore, seven proteins self-interact, four strongly, pointing to subunit multiplicity in the holoenzyme. Six protein subunits interact directly with MRP RNA and four with pre-rRNA. A comparative analysis with existing data for the yeast and human RNase P/MRP systems enables confident identification of Pop1p, Pop4p and Rpp1p as subunits that lie at the enzyme core, with probable addition of Pop5p and Pop3p. Rmp1p is confirmed as an integral subunit, presumably associating preferentially with RNase MRP, rather than RNase P, via interactions with Snm1p and MRP RNA. Snm1p and Rmp1p may act together to assist enzyme specificity, though roles in substrate binding are also indicated for Pop4p and Pop6p. The results provide further evidence of a conserved eukaryotic RNase P/MRP architecture and provide a strong basis for studies of enzyme assembly and subunit function
Spin Fluctuations and the Magnetic Phase Diagram of ZrZn2
The magnetic properties of the weak itinerant ferromagnet ZrZn_2 are analyzed
using Landau theory based on a comparison of density functional calculations
and experimental data as a function of field and pressure. We find that the
magnetic properties are strongly affected by the nearby quantum critical point,
even at zero pressure; LDA calculations neglecting quantum critical spin
fluctuations overestimate the magnetization by a factor of approximately three.
Using renormalized Landau theory, we extract pressure dependence of the
fluctuation amplitude. It appears that a simple scaling based on the
fluctuation-dissipation theorem provides a good description of this pressure
dependence.Comment: 4 revtex page
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