60 research outputs found
Response, relaxation and transport in unconventional superconductors
We investigate the collision-limited electronic Raman response and the
attenuation of ultrasound in spin-singlet d-wave superconductors at low
temperatures. The dominating elastic collisions are treated within a t-matrix
approximation, which combines the description of weak (Born) and strong
(unitary) impurity scattering. In the long wavelength limit a two-fluid
description of both response and transport emerges. Collisions are here seen to
exclusively dominate the relaxational dynamics of the (Bogoliubov)
quasiparticle system and the analysis allows for a clear connection of response
and transport phenomena. When applied to quasi-2-d superconductors like the
cuprates, it turns out that the transport parameter associated with the Raman
scattering intensity for B1g and B2g photon polarization is closely related to
the corresponding components of the shear viscosity tensor, which dominates the
attenuation of ultrasound. At low temperatures we present analytic solutions of
the transport equations, resulting in a non-power-law behavior of the transport
parameters on temperature.Comment: 22 pages, 3 figure
Electronic Raman response in anisotropic metals
Using a generalized response theory we derive the electronic Raman response
function for metals with anisotropic relaxation rates. The calculations account
for the long--range Coulomb interaction and treat the collision operator within
a charge conserving relaxation time approximation. We extend earlier treatments
to finite wavenumbers () and incorporate inelastic
electron--electron scattering besides elastic impurity scattering. Moreover we
generalize the Lindhard density response function to the Raman case. Numerical
results for the quasiparticle scattering rate and the Raman response function
for cuprate superconductors are presented.Comment: 5 pages, 4figures. accepted in PRB (Brief Report), in pres
Nodes of the Gap Function and Anomalies in Thermodynamic Properties of Superfluid He
Departures of thermodynamic properties of three-dimensional superfluid He
from the predictions of BCS theory are analyzed. Attention is focused on
deviations of the ratios and
from their BCS values, where is the pairing gap at zero
temperature, is the critical temperature, and and are the
superfluid and normal specific heats. We attribute these deviations to the
momentum dependence of the gap function , which becomes well
pronounced when this function has a pair of nodes lying on either side of the
Fermi surface. We demonstrate that such a situation arises if the P-wave
pairing interaction , evaluated at the Fermi surface, has a sign
opposite to that anticipated in BCS theory. Taking account of the momentum
structure of the gap function, we derive a closed relation between the two
ratios that contains no adjustable parameters and agrees with the experimental
data. Some important features of the effective pairing interaction are inferred
from the analysis.Comment: 17 pages, 4 figure
Surface Roughness and Effective Stick-Slip Motion
The effect of random surface roughness on hydrodynamics of viscous
incompressible liquid is discussed. Roughness-driven contributions to
hydrodynamic flows, energy dissipation, and friction force are calculated in a
wide range of parameters. When the hydrodynamic decay length (the viscous wave
penetration depth) is larger than the size of random surface inhomogeneities,
it is possible to replace a random rough surface by effective stick-slip
boundary conditions on a flat surface with two constants: the stick-slip length
and the renormalization of viscosity near the boundary. The stick-slip length
and the renormalization coefficient are expressed explicitly via the
correlation function of random surface inhomogeneities. The effective
stick-slip length is always negative signifying the effective slow-down of the
hydrodynamic flows by the rough surface (stick rather than slip motion). A
simple hydrodynamic model is presented as an illustration of these general
hydrodynamic results. The effective boundary parameters are analyzed
numerically for Gaussian, power-law and exponentially decaying correlators with
various indices. The maximum on the frequency dependence of the dissipation
allows one to extract the correlation radius (characteristic size) of the
surface inhomogeneities directly from, for example, experiments with torsional
quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure
Mass coupling and ^3$He in a torsion pendulum
We present results of the and period shift, , for He
confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is
compressed uniaxially by 10% along a direction aligned to the torsion pendulum
axis and was grown within a 400 m tall pancake (after compression) similar
to an Andronikashvili geometry. The result is a high pendulum able to
resolve and mass coupling of the impurity-limited He over the
whole temperature range. After measuring the empty cell background, we filled
the cell above the critical point and observe a temperature dependent period
shift, , between 100 mK and 3 mK that is 2.9 of the period shift
(after filling) at 100 mK. The due to the He decreases by an order
of magnitude between 100 mK and 3 mK at a pressure of bar. We
compare the observable quantities to the corresponding calculated and
period shift for bulk He.Comment: 8 pages, 3 figure
Dissipation Mechanisms near the Superfluid 3He Transition in Aerogel
金沢大学理学部The dissipation mechanisms (Q-1) near the superfluid 3He transition in aerogel was investigated using the torsion pendulum technique. It was found that with pure 3He the Q-1 decerases at the onset of superfluidity. It was also found that when phase separated 3He-4He mixtures are introduced into the aerogel, the Q-1 does not decrease as rapidly and eventually increases for the highest 4He content. A model for the related attenuation of transverse sound α that takes into account elastic and inelastic scattering processes was also presented
Thermal transport of helium-3 in a strongly confining channel
In a neutral system such as liquid helium-3, transport of mass, heat, and
spin provide information analogous to electrical counterparts in metals,
superconductors and topological materials. Of particular interest is transport
in strongly confining channels of height approaching the superfluid coherence
length, where new quantum states are found and excitations bound to surfaces
and edges should be present. Here we report on the thermal conduction of
helium-3 in a 1.1~m high microfabricated channel. In the normal state we
observe a diffusive thermal conductivity that is approximately temperature
independent, consistent with recent work on the interference of bulk and
boundary scattering. In the superfluid state we measure diffusive thermal
transport in the absence of thermal counterflow. An anomalous thermal response
is also detected in the superfluid which we suggest may arise from a flux of
surface excitations.Comment: A supplement is available. Please contact Jeevak Parpia
([email protected]) if you would like the supplement as wel
On the problem of catastrophic relaxation in superfluid 3-He-B
In this Letter we discussed the parametric instability of texture of
homogeneous (in time) spin precession, explaining how spatial inhomogeneity of
the texture may change the threshold of the instability in comparison with
idealized spatial homogeneous case, considered in our JETP Letter \textbf{83},
530 (2006), cond-mat/0605386. This discussion is inspired by critical Comment
of I.A. Fomin (cond-mat/0606760) related to the above questions. In addition we
considered here results of direct numerical simulations of the full
Leggett-Takagi equation of motion for magnetization in superfluid 3He-B and
experimental data for magnetic field dependence of the catastrophic relaxation,
that provide solid support of the theory of this phenomenon, presented in our
2006 JETP Letter.Comment: 5 pages, 1 fig. included, JETP Lett. style, submitted to JETP Lett.
as response to Comment cond-mat/060676
Electronic Raman Scattering in Nearly Antiferromagnetic Fermi Liquids
A theory of electronic Raman scattering in nearly antiferromagnetic Fermi
liquids is constructed using the phenomenological electron-electron interaction
introduced by Millis, Monien, and Pines. The role of "hot spots" and their
resulting signatures in the channel dependent Raman spectra is highlighted, and
different scaling regimes are addressed. The theory is compared to Raman
spectra taken in the normal state of overdoped
BiSrCaCuO, and it is shown that many features of
the symmetry dependent spectra can be explained by the theory.Comment: 3 pages + 4 figures, SNS97 Conference Proceeding
A Consistent Picture of Electronic Raman Scattering and Infrared Conductivity in the Cuprates
Calculations are presented for electronic Raman scattering and infrared
conductivity in a superconductor including the effects of
elastic scattering via anisotropic impurities and inelastic spin-fluctuation
scattering. A consistent description of experiments on optimally doped Bi-2212
is made possible by considering the effects of correlations on both inelastic
and elastic scattering.Comment: 4 pages Revtex, 5 embedded eps file
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