391 research outputs found
Universal Scaling Behavior of Anomalous Hall Effect and Anomalous Nernst Effect in Itinerant Ferromagnets
Anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) in a variety of
ferromagnetic metals including pure metals, oxides, and chalcogenides, are
studied to obtain unified understandings of their origins. We show a universal
scaling behavior of anomalous Hall conductivity as a function of
longitudinal conductivity over five orders of magnitude, which is
well explained by a recent theory of the AHE taking into account both the
intrinsic and extrinsic contributions. ANE is closely related with AHE and
provides us with further information about the low-temperature electronic state
of itinerant ferromagnets. Temperature dependence of transverse Peltier
coefficient shows an almost similar behavior among various
ferromagnets, and this behavior is in good agreement quantitatively with that
expected from the Mott rule.Comment: 4pages, 4figures, 1tabl
Ambipolar Nernst effect in NbSe
The first study of Nernst effect in NbSe reveals a large quasi-particle
contribution with a magnitude comparable and a sign opposite to the vortex
signal. Comparing the effect of the Charge Density Wave(CDW) transition on Hall
and Nernst coefficients, we argue that this large Nernst signal originates from
the thermally-induced counterflow of electrons and holes and indicates a
drastic change in the electron scattering rate in the CDW state. The results
provide new input for the debate on the origin of the anomalous Nernst signal
in high-T cuprates.Comment: 5 pages including 4 figure
Integral equation for inhomogeneous condensed bosons generalizing the Gross-Pitaevskii differential equation
We give here the derivation of a Gross-Pitaevskii--type equation for
inhomogeneous condensed bosons. Instead of the original Gross-Pitaevskii
differential equation, we obtain an integral equation that implies less
restrictive assumptions than are made in the very recent study of Pieri and
Strinati [Phys. Rev. Lett. 91 (2003) 030401]. In particular, the Thomas-Fermi
approximation and the restriction to small spatial variations of the order
parameter invoked in their study are avoided.Comment: Phys. Rev. A (accepted
Path-decomposition expansion and edge effects in a confined magnetized free-electron gas
Path-integral methods can be used to derive a `path-decomposition expansion'
for the temperature Green function of a magnetized free-electron gas confined
by a hard wall. With the help of this expansion the asymptotic behaviour of the
profiles for the excess particle density and the electric current density far
from the edge is determined for arbitrary values of the magnetic field
strength. The asymptotics are found to depend sensitively on the degree of
degeneracy. For a non-degenerate electron gas the asymptotic profiles are
essentially Gaussian (albeit modulated by a Bessel function), on a length scale
that is a function of the magnetic field strength and the temperature. For a
completely degenerate electron gas the asymptotic behaviour is again
proportional to a Gaussian, with a scale that is the magnetic length in this
case. The prefactors are polynomial and logarithmic functions of the distance
from the wall, that depend on the number of filled Landau levels . As a
consequence, the Gaussian asymptotic decay sets in at distances that are large
compared to the magnetic length multiplied by .Comment: 16 pages, 2 figures, submitted to J. Phys. A: Math. Gen; corrected
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Quantum kinetic approach to the calculation of the Nernst effect
We show that the strong Nernst effect observed recently in amorphous
superconducting films far above the critical temperature is caused by the
fluctuations of the superconducting order parameter. We employ the quantum
kinetic approach for the derivation of the Nernst coefficient. We present here
the main steps of the calculation and discuss some subtle issues that we
encountered while calculating the Nernst coefficient. In particular, we
demonstrate that in the limit T=0 the contribution of the magnetization ensures
the vanishing of the Nernst signal in accordance with the third law of
thermodynamics. We obtained a striking agreement between our theoretical
calculations and the experimental data in a broad region of temperatures and
magnetic fields.Comment: 24 pages, 13 figure
Fermi-liquid theory of the surface impedance of a metal in a normal magnetic field
In this paper we present detailed theoretical analysis of the frequency
and/or magnetic field dependence of the surface impedance of a metal at the
anomalous skin effect. We calculate the surface impedance in the presence of a
magnetic field directed along the normal to the metal surface. The effects of
the Fermi-liquid interactions on the surface impedance are studied. It is shown
that the cyclotron resonance in a normal magnetic field may be revealed {\it
only and exclusively} in such metals whose Fermi surfaces include segments
where its Gaussian curvature turns zero. The results could be applied to
extract extra informations concerning local anomalies in the Fermi surface
curvature in conventional and quasi-two-dimensional metals.Comment: 10 pages, 1 figure, text added and rearranged, computational details
are moved into Appendice
Interaction of the Electromagnetic p-Waves with Thin Metal Films
For the first time it is shown that for thin metallic films thickness of
which not exceed thickness of skin-layer, the problem allows analytical
solution for arbitrary boundary value problems. The analysis of dependence of
coefficients of transmission, reflection and absorbtion on angle incidence,
thickness of films and coefficient of specular reflection is carried out.Comment: 15 pages, 9 figure
Correlations in a confined magnetized free-electron gas
Equilibrium quantum statistical methods are used to study the pair
correlation function for a magnetized free-electron gas in the presence of a
hard wall that is parallel to the field. With the help of a path-integral
technique and a Green function representation the modifications in the
correlation function caused by the wall are determined both for a
non-degenerate and for a completely degenerate gas. In the latter case the
asymptotic behaviour of the correlation function for large position differences
in the direction parallel to the wall and perpendicular to the field, is found
to change from Gaussian in the bulk to algebraic near the wall.Comment: 24 pages, 10 figures, submitted to J. Phys. A: Math. Ge
G-Quadruplex Dynamics Contribute To Regulation Of Mitochondrial Gene Expression
Single-stranded DNA or RNA sequences rich in guanine (G) can adopt non-canonical structures known as G-quadruplexes (G4). Mitochondrial DNA (mtDNA) sequences that are predicted to form G4 are enriched on the heavy-strand and have been associated with formation of deletion breakpoints. Increasing evidence supports the ability of mtDNA to form G4 in cancer cells; however, the functional roles of G4 structures in regulating mitochondrial nucleic acid homeostasis in non-cancerous cells remain unclear. Here, we demonstrate by live cell imaging that the G4-ligand RHPS4 localizes primarily to mitochondria at low doses. We find that low doses of RHPS4 do not induce a nuclear DNA damage response but do cause an acute inhibition of mitochondrial transcript elongation, leading to respiratory complex depletion. We also observe that RHPS4 interferes with mtDNA levels or synthesis both in cells and isolated mitochondria. Importantly, a mtDNA variant that increases G4 stability and anti-parallel G4-forming character shows a stronger respiratory defect in response to RHPS4, supporting the conclusion that mitochondrial sensitivity to RHPS4 is G4-mediated. Taken together, our results indicate a direct role for G4 perturbation in mitochondrial genome replication, transcription processivity, and respiratory function in normal cells
The onset of the vortex-like Nernst signal above Tc in La_{2-x}Sr_xCuO_4 and Bi_2Sr_{2-y}La_yCuO_6
The diffusion of vortices down a thermal gradient produces a Josephson signal
which is detected as the vortex Nernst effect. In a recent report, Xu et al.,
Nature 406, 486 (2000), an enhanced Nernst signal identified with vortex-like
excitations was observed in a series of La_{2-x}Sr_xCuO_4 (LSCO) crystals at
temperatures 50-100 K above T_c. To pin down the onset temperature T_{\nu} of
the vortex-like signal in the lightly doped regime (0.03 < x < 0.07), we have
re-analyzed in detail the carrier contribution to the Nernst signal. By
supplementing new Nernst measurements with thermopower and Hall-angle data, we
isolate the off-diagonal Peltier conductivity \alpha_{xy} and show that its
profile provides an objective determination of T_{\nu}. With the new results,
we revise the phase diagram for the fluctuation regime in LSCO to accomodate
the lightly doped regime. In the cuprate Bi_2Sr_{2-y}La_yCuO_6, we find that
the carrier contribution is virtually negligible for y in the range 0.4-0.6.
The evidence for an extended temperature interval with vortex-like excitations
is even stronger in this system. Finally, we discuss how T_{\nu} relates to the
pseudogap temperature T* and the implications of strong fluctuations between
the pseudogap state and the d-wave superconducting state.Comment: 10 pages, 10 figure
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