9 research outputs found
Unconventional superconductivity in iron-base superconductors in a three-band model
Iron-base superconductors exhibits features of systems where the
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase, a superconducting state with
non-zero total momentum of Cooper pairs, is actively sought. Experimental and
theoretical evidence points strongly to the FFLO phase in these materials above
the Pauli limit. In this article we discuss the ground state of iron-base
superconductors near the critical magnetic field and the full phase
diagram for pnictides in case of intra-band pairing, in a three-band model with
symmetry.Comment: RevTeX, 5 pages, 3 figures. Presented on "XVI National Conference of
Superconductivity", October 7-12, 2013, Zakopane, Polan
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
Particle and energy transport in strongly driven one-dimensional quantum systems
This Dissertation concerns the transport properties of a strongly–correlated one–dimensional system
of spinless fermions, driven by an external electric field which induces the flow of charges and energy
through the system. Since the system does not exchange information with the environment, the
evolution can be accurately followed to arbitrarily long times by solving numerically the time–dependent
Schrödinger equation, going beyond Kubo’s linear response theory.
The thermoelectric response of the system is here characterized, using the ratio of the induced
energy and particle currents, in the nonequilibrium state under the steady applied electric field. Even
though the equilibrium response can be reached for vanishingly small driving, strong fields produce
quantum–mechanical Bloch oscillations in the currents, which disrupt the proportionality of the currents.
The effects of the driving on the local state of the ring are analyzed via the reduced density matrix of
small subsystems. The local entropy density can be defined and shown to be consistent with the laws of
thermodynamics for quasistationary evolution. Even integrable systems are shown to thermalize under
driving, with heat being produced via the Joule effect by the flow of currents. The spectrum of the
reduced density matrix is shown to be distributed according the Gaussian unitary ensemble predicted by
random–matrix theory, both during driving and a subsequent relaxation.
The first fully–quantum model of a thermoelectric couple is realized by connecting two correlated
quantum wires. The field is shown to produce heating and cooling at the junctions according to the
Peltier effect, by mapping the changes in the local entropy density. In the quasiequilibrium regime, a
local temperature can be defined, at the same time verifying that the subsystems are in a Gibbs thermal
state. The gradient of temperatures, established by the external field, is shown to counterbalance the
flow of energy in the system, terminating the operation of the thermocouple. Strong applied fields lead
to new nonequilibrium phenomena. At the junctions, observable Bloch oscillations of the density of
charge and energy develop at the junctions. Moreover, in a thermocouple built out of Mott insulators, a
sufficiently strong field leads to a dynamical transition reversing the sign of the charge carriers and the
Peltier effect
The Fulde-Ferrell-Larkin-Ovchinnikov state in pnictides
Fe-based superconductors (FeSC) exhibit all the properties of systems that allow the formation of a superconducting phase with oscillating order parameter, called the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. By the analysis of the Cooper pair susceptibility in two-band FeSC, such systems are shown to support the existence of a FFLO phase, regardless of the exhibited order parameter symmetry. We also show the state with nonzero Cooper pair momentum, in superconducting FeSC with ∼cos(k x )⋅cos(k y ) symmetry, to be the ground state of the system in a certain parameter range.Fe-based superconductors (FeSC) exhibit all the properties of systems that allow the formation of a superconducting phase with oscillating order parameter, called the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. By the analysis of the Cooper pair susceptibility in two-band FeSC, such systems are shown to support the existence of a FFLO phase, regardless of the exhibited order parameter symmetry. We also show the state with nonzero Cooper pair momentum, in superconducting FeSC with ∼cos(k x )⋅cos(k y ) symmetry, to be the ground state of the system in a certain parameter range
Specific heat study of Fulde–Ferrell–Larkin–Ovchinnikov superconducting states in multibands materials - Iron-based Systems
The Fulde-Ferrell-Larkin-Ovchinnikov phase is the superconducting state for which the Cooper pairs have non-zero total momentum. From the time of conception of this phase, many groups have been searching for a realization of the state. Here we describe a proposal of experimental verification of this state in the case of multibands systems, by carrying out the specific-heat measurement
The Fulde–Ferrell–Larkin–Ovchinnikov State in Pnictides
Fe-based superconductors (FeSC) exhibit all the properties of systems that
allow the formation of a superconducting phase with oscillating order
parameter, called the Fulde--Ferrell--Larkin--Ovchinnikov (FFLO) phase. By the
analysis of the Cooper pair susceptibility in two-band FeSC, such systems are
shown to support the existence of a FFLO phase, regardless of the exhibited
order parameter symmetry. We also show the state with nonzero Cooper pair
momentum, in superconducting FeSC with
symmetry, to be the ground state of the system in a certain parameter range.Comment: 8 pages, 4 figures Journal of Low Temperature Physics, (2013