34 research outputs found
c-axis Optical Conductivity in Cuprates
We investigate the c-axis optical conductivity and d.c. resistivity of
cuprate superconductors in the normal state. Assuming that the interlayer
hopping is incoherent we express the conductivity with planar spectral
functions obtained (i) from angle-resolved photoemission experiments, (ii)
using marginal Fermi liquid ansatz, and (iii) with the finite-temperature
Lanczos method for finite two-dimensional systems described by the t-J model.
Here in the low doping regime a pseudo-gap opening in the density of states
appears to be responsible for a semimetallic-like behavior of the D.C.
resistivity. In the optimally doped regime we find an anomalous relaxation
rate. Analytically this result is reproduced with the use of the marginal Fermi
liquid ansatz for the self energy with parameters obtained from the exact
diagonalization results.Comment: LT22 - submitted to Physica
Energy current and energy fluctuations in driven quantum wires
We discuss the energy current and the energy fluctuations in an isolated
quantum wire driven far from equilibrium. The system consists of interacting
spinless fermions and is driven by a time--dependent magnetic flux. The energy
current is defined by the continuity equation for the energy density which is
derived both for homogeneous as well as for inhomogeneous systems. Since the
total energy is not conserved in the driven system, the continuity equation
includes the source terms which are shown to represent the Joule heating
effects. For short times and weak drivings the energy current agrees with the
linear response theory. For stronger fields or longer times of driving the
system enters the quasiequilibrium regime when the energy current gradually
diminishes due to the heating effects. Finally, for even stronger driving the
energy current is shown to undergo a damped Bloch oscillations. The energy
spread also increases upon driving. However, the time--dependence of this
quantity in the low field regime is quite unexpected since it is determined
mostly by the time of driving being quite independent of the instantaneous
energy of the system.Comment: 9 pages, 2 figures, Proc. NATO Adv. Research Workshop Nanotechnology
in the security systems, Ed. S. Kruchinin, Yalta, Ukraine, 201
Exciton Recombination in One-Dimensional Organic Mott Insulators
We present a theory for the recombination of (charged) holons and doublons in
one-dimensional organic Mott insulators, which is responsible for the decay of
a photoexcited metallic state. Due to the charge-spin separation, the dominant
mechanism for recombination at low density of charges involves a multi-phonon
emission. We show that a reasonable coupling to phonons is sufficient to
explain the fast recombination observed by pump-probe experiments in
ET-FTCNQ, whereby we can also account for the measured pressure dependence
of the recombination rate.Comment: 5 + 3 pages, 2 figure
Freezing of spin dynamics and omega/T scaling in underdoped cuprates
The memory function approach to spin dynamics in doped antiferromagnetic
insulator combined with the assumption of temperature independent static spin
correlations and constant collective mode damping leads to omega/T scaling in a
broad range. The theory involving a non universal scaling parameter is used to
analyze recent inelastic neutron scattering results for underdoped cuprates.
Adopting modified damping function also the emerging central peak in low-doped
cuprates at low temperatures can be explained within the same framework.Comment: 4 pages, 5 figures; to appear in Journal of Physics: Conference
Series (ICM2009 Conference, Karlsruhe, Germany