963 research outputs found
All Optical Measurement Proposed for the Photovoltaic Hall Effect
We propose an all optical way to measure the recently proposed "photovoltaic
Hall effect", i.e., a DC Hall effect induced by a circularly polarized light in
the absence of static magnetic fields. For this, we have calculated the Faraday
rotation angle induced by the photovoltaic Hall effect with the Kubo formula
extended for photovoltaic optical response in the presence of strong AC
electric fields treated with the Floquet formalism. We also point out the
possibility of observing the effect in three-dimensional graphite, and more
generally in multi-band systems such as materials described by the dp-model.Comment: 5 page
Confinement Phase in Carbon-Nanotubes and the Extended Massive Schwinger Model
Carbon nanotube with electric fluxes confined in one dimension is studied. We
show that a Coulomb interaction \propto |x| leads to a confinement phase with
many properties similar to QCD in 4D. Low-energy physics is described by the
massive Schwinger model with multi-species fermions labeled by the band and
valley indices. We propose two means to detect this state. One is through an
optical measurement of the exciton spectrum, which has been calculated via the
't Hooft-Berknoff equation with the light-front field theory. We show that the
Gell-Mann-Oakes-Renner relation is satisfied by a dark exciton. The second is
the nonlinear transport which is related to Coleman's "half-asymptotic" state.Comment: 5 pages, 3 figure
Nonlinear Transport in One-Dimensional Mott Insulator in Strong Electric Fields
Time-dependent Schroedinger's equation is integrated for a one-dimensional
strongly-correlated electron system driven by large electric fields. For larger
electric fields, many-body Landau-Zener tunneling takes place at anti-crossings
of the many-body energy levels. The nonlinear - characteristics as well
as the time dependence of the energy expectation value are obtained. The energy
of the Mott insulator in electric fields shows a saturation, which suggests a
dynamical localization in energy space of many-body wave functions.Comment: 3 pages, 3 figures, Proceedings of SCES'04 (Karlsruhe
Dielectric breakdown of Mott insulators in dynamical mean-field theory
Using nonequilibrium dynamical mean-field theory, we compute the time
evolution of the current in a Mott insulator after a strong electric field is
turned on. We observe the formation of a quasistationary state in which the
current is almost time-independent although the system is constantly excited.
At moderately strong fields this state is stable for quite long times. The
stationary current exhibits a threshold behavior as a function of the field, in
which the threshold increases with the Coulomb interaction and vanishes as the
metal-insulator transition is approached.Comment: 4 pages, 3 figure
Probing and controlling spin chirality in Mott insulators by circularly polarized laser
Scalar spin chirality, a three-body spin correlation that breaks
time-reversal symmetry, is revealed to couple directly to circularly polarized
laser. This is shown by the Floquet formalism for the periodically driven
repulsive Hubbard model with a strong-coupling expansion. A systematic
derivation of the effective low-energy Hamiltonian for a spin degree of freedom
reveals that the coupling constant for scalar spin chirality can become
significant for a situation in which the driving frequency and the on-site
interaction are comparable. This implies that the scalar chirality can be
induced by circularly polarized lights, or that it can be used conversely for
probing the chirality in Mott insulators as a circular dichroism.Comment: 10 pages, 8 figure
Chiral pumping effect induced by rotating electric fields
We propose an experimental setup using 3D Dirac semimetals to access a novel
phenomenon induced by the chiral anomaly. We show that the combination of a
magnetic field and a circularly polarized laser induces a finite charge density
with an accompanying axial current. This is because the circularly polarized
laser breaks time-reversal symmetry and the Dirac point splits into two Weyl
points, which results in an axial-vector field. We elucidate the appearance of
the axial-vector field with the help of the Floquet theory by deriving an
effective Hamiltonian for high-frequency electric fields. This anomalous charge
density, i.e. the chiral pumping effect, is a phenomenon reminiscent of the
chiral magnetic effect with a chiral chemical potential. We explicitly compute
the pumped density and the axial-current expectation value. We also take
account of coupling to the chiral magnetic effect to calculate a balanced
distribution of charge and chirality in a material that behaves as a chiral
battery.Comment: 6 pages, 3 figures; a new section added to discuss coupling of the
CPE and the CME, a wrong sign corrected, typos fixed, elaborated for better
readabilit
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