731 research outputs found
Bose-Fermi Mixtures in One Dimension
We analyze the phase stability and the response of a mixture of bosons and
spin-polarized fermions in one dimension (1D). Unlike in 3D, phase separation
happens for low fermion densities. The dynamics of the mixture at low energy is
independent of the spin-statistics of the components, and zero-sound-like modes
exist that are essentially undamped.Comment: 5 pages; 1 figur
The mean energy, strength and width of triple giant dipole resonances
We investigate the mean energy, strength and width of the triple giant dipole
resonance using sum rules.Comment: 12 page
Non-equilibrium Plasmons in a Quantum Wire Single Electron Transistor
We analyze a single electron transistor composed of two semi-infinite one
dimensional quantum wires and a relatively short segment between them. We
describe each wire section by a Luttinger model, and treat tunneling events in
the sequential approximation when the system's dynamics can be described by a
master equation. We show that the steady state occupation probabilities in the
strongly interacting regime depend only on the energies of the states and
follow a universal form that depends on the source-drain voltage and the
interaction strength.Comment: 4 pages, 3 figures. To appear in the Phys. Rev. Let
Two dimensional anisotropic non Fermi-liquid phase of coupled Luttinger liquids
We show using bosonization techniques, that strong forward scattering
interactions between one dimensional spinless Luttinger liquids (LL) can
stabilize a phase where charge-density wave, superconducting and transverse
single particle hopping perturbations are irrelevant. This new phase retains
its LL like properties in the directions of the chains, but with relations
between exponents modified by the transverse interactions, whereas, it is a
perfect insulator in the transverse direction. The mechanism that stabilizes
this phase are strong transverse charge density wave fluctuations at
incommensurate wavevector, which frustrates crystal formation by preventing
lock-in of the in-chain density waves.Comment: (4 pages, 2 figures
A Solvable Model of Interacting Fermions in Two Dimensions
We introduce and study an exactly solvable model of several species of
fermions in which particles interact pairwise through a mutual magnetic field;
the interaction operates only between particles belonging to different species.
After an unitary transformation, the model reduces to one in which each
particle sees a magnetic field which depends on the total numbers of particles
of all the other species; this may be viewed as the mean-field model for a
class of anyonic theories. Our model is invariant under charge conjugation C
and the product PT (parity and time reversal). For the special case of two
species, we examine various properties of this system, such as the Hall
conductivity, the wave function overlap arising from the transfer of one
particle from one species to another, and the one-particle off-diagonal density
matrix. Our model is a generalization of a recently introduced solvable model
in one dimension.Comment: Revtex, 7 page
Boundary Effects on Spectral Properties of Interacting Electrons in One Dimension
The single electron Green's function of the one-dimensional
Tomonaga-Luttinger model in the presence of open boundaries is calculated with
bosonization methods. We show that the critical exponents of the local spectral
density and of the momentum distribution change in the presence of a boundary.
The well understood universal bulk behavior always crosses over to a boundary
dominated regime for small energies or small momenta. We show this crossover
explicitly for the large-U Hubbard model in the low-temperature limit.
Consequences for photoemission experiments are discussed.Comment: revised and reformatted paper to appear in Phys. Rev. Lett. (Feb.
1996). 5 pages (revtex) and 3 embedded figures (macro included). A complete
postscript file is available from http://FY.CHALMERS.SE/~eggert/luttinger.ps
or by request from [email protected]
Fluctuation theorem for constrained equilibrium systems
We discuss the fluctuation properties of equilibrium chaotic systems with
constraints such as iso-kinetic and Nos\'e-Hoover thermostats. Although the
dynamics of these systems does not typically preserve phase-space volumes, the
average phase-space contraction rate vanishes, so that the stationary states
are smooth. Nevertheless finite-time averages of the phase-space contraction
rate have non-trivial fluctuations which we show satisfy a simple version of
the Gallavotti-Cohen fluctuation theorem, complementary to the usual
fluctuation theorem for non-equilibrium stationary states, and appropriate to
constrained equilibrium states. Moreover we show these fluctuations are
distributed according to a Gaussian curve for long-enough times. Three
different systems are considered here, namely (i) a fluid composed of particles
interacting with Lennard-Jones potentials; (ii) a harmonic oscillator with
Nos\'e-Hoover thermostatting; (iii) a simple hyperbolic two-dimensional map.Comment: To appear in Phys. Rev.
Pressure dependence of the single particle excitation in the charge-density-wave CeTe system
We present new data on the pressure dependence at 300 K of the optical
reflectivity of CeTe, which undergoes a charge-density-wave (CDW) phase
transition well above room temperature. The collected data cover an
unprecedented broad spectral range from the infrared up to the ultraviolet,
which allows a robust determination of the gap as well as of the fraction of
the Fermi surface affected by the formation of the CDW condensate. Upon
compressing the lattice there is a progressive closing of the gap inducing a
transfer of spectral weight from the gap feature into the Drude component. At
frequencies above the CDW gap we also identify a power-law behavior, consistent
with findings along the Te series (i.e., chemical pressure) and
suggestive of a Tomonaga-Luttinger liquid scenario at high energy scales. This
newest set of data is placed in the context of our previous investigations of
this class of materials and allows us to revisit important concepts for the
physics of CDW state in layered-like two-dimensional systems
Quantum Scattering in Quasi-1D Cylindrical Confinement
Finite size effects alter not only the energy levels of small systems, but
can also lead to new effective interactions within these systems. Here the
problem of low energy quantum scattering by a spherically symmetric short range
potential in the presence of a general cylindrical confinement is investigated.
A Green's function formalism is developed which accounts for the full 3D nature
of the scattering potential by incorporating all phase-shifts and their
couplings. This quasi-1D geometry gives rise to scattering resonances and
weakly localized states, whose binding energies and wavefunctions can be
systematically calculated. Possible applications include e.g. impurity
scattering in ballistic quasi-1D quantum wires in mesoscopic systems and in
atomic matter wave guides. In the particular case of parabolic confinement, the
present formalism can also be applied to pair collision processes such as
two-body interactions. Weakly bound pairs and quasi-molecules induced by the
confinement and having zero or higher orbital angular momentum can be
predicted, such as p- and d-wave pairings.Comment: Extended version of quant-ph/050319
Local Fields without Restrictions on the Spectrum of 4-Momentum Operator and Relativistic Lindblad Equation
Quantum theory of Lorentz invariant local scalar fields without restrictions
on 4-momentum spectrum is considered. The mass spectrum may be both discrete
and continues and the square of mass as well as the energy may be positive or
negative. Such fields can exist as part of a hidden matter in the Universe if
they interact with ordinary fields very weakly. Generalization of
Kallen-Lehmann representation for propagators of these fields is found. The
considered generalized fields may violate CPT- invariance. Restrictions on
mass-spectrum of CPT-violating fields are found. Local fields that annihilate
vacuum state and violate CPT- invariance are constructed in this scope. Correct
local relativistic generalization of Lindblad equation for density matrix is
written for such fields. This generalization is particulary needed to describe
the evolution of quantum system and measurement process in a unique way.
Difficulties arising when the field annihilating the vacuum interacts with
ordinary fields are discussed.Comment: Latex 23 pages, sent to "Foundations of Physics
- …