1,834 research outputs found
All Optical Measurement Proposed for the Photovoltaic Hall Effect
Full text linkWe 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
Full text linkCarbon 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
Vacuum Instability in Electric Fields via AdS/CFT: Euler-Heisenberg Lagrangian and Planckian Thermalization
Full text linkWe analyze vacuum instability of strongly coupled gauge theories in a
constant electric field using AdS/CFT correspondence. The model is the N=2
1-flavor supersymmetric large N_c QCD in the strong 't Hooft coupling limit. We
calculate the Euler-Heisenberg effective Lagrangian L(E), which encodes the
nonlinear response and the quantum decay rate of the vacuum in a background
electric field E, from the complex D-brane action in AdS/CFT. We find that the
decay rate given by Im L(E) becomes nonzero above a critical electric field set
by the confining force between quarks. A large-E expansion of Im L(E) is found
to coincide with that of the Schwinger effects in QED, replacing its electron
mass by the confining force. Then, the time-dependent response of the system in
a strong electric field is solved non-perturbatively, and we observe a
universal thermalization at a shortest timescale "Planckian thermalization
time" t ~ 1/T ~ E^{-1/2}. Here, T is an effective temperature which quarks feel
in the nonequilibrium state with nonzero electric current, calculated in
AdS/CFT as a Hawking temperature. Stronger electric fields accelerate the
thermalization, and for a realistic value of the electric field in RHIC
experiment, we obtain t ~ 1 [fm/c], which is consistent with the believed
value.Comment: 41 page
Nonequilibrium magnetic and superconducting phases in the two-dimensional Hubbard model coupled to electrodes
Full text linkA theory is presented for a nonequilibrium phase transition in the
two-dimensional Hubbard model coupled to electrodes. Nonequilibrium magnetic
and superconducting phase diagram is determined by the Keldysh method, where
the electron correlation is treated in the fluctuation exchange approximation.
The nonequilibrium distribution function in the presence of electron
correlation is evoked to capture a general feature in the phase diagram.Comment: 6 pages, 3 figure
Nonlinear Transport in One-Dimensional Mott Insulator in Strong Electric Fields
Full text linkTime-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
Nonadiabatic Nonlinear Optics and Quantum Geometry -- Application to the Twisted Schwinger Effect
Get PDFWe study the tunneling mechanism of nonlinear optical processes in solids
induced by strong coherent laser fields. The theory is based on an extension of
the Landau-Zener model with nonadiabatic geometric effects. In addition to the
rectification effect known previously, we find two effects, namely perfect
tunneling and counterdiabaticity at fast sweep speed. We apply this theory to
the twisted Schwinger effect, i.e., nonadiabatic pair production of particles
by rotating electric fields, and find a nonperturbative generation mechanism of
the opto-valley polarization and photo-current in Dirac and Weyl fermions.Comment: 24 pages, Accepted by SciPos
Probing and controlling spin chirality in Mott insulators by circularly polarized laser
Full text linkScalar 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
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