352 research outputs found
Spin gap and Luttinger liquid description of the NMR relaxation in carbon nanotubes
Recent NMR experiments by Singer et al. [Singer et al. Phys. Rev. Lett. 95,
236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon
nanotubes with an energy gap evident at low temperatures. Here, a comprehensive
theory for the magnetic field and temperature dependent NMR 13C spin-lattice
relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low
temperature properties are governed by a gapped relaxation due to a spin gap (~
30K), which crosses over smoothly to the Luttinger liquid behaviour with
increasing temperature.Comment: 5 pages, 1 figure, 1 tabl
Wick's Theorem and a New Perturbation Theory Around the Atomic Limit of Strongly Correlated Electron Systems
A new type of perturbation expansion in the mixing of localized orbitals
with a conduction-electron band in the Anderson model is
presented. It is built on Feynman diagrams obeying standard rules. The local
correlations of the unperturbed system (the atomic limit) are included exactly,
no auxiliary particles are introduced. As a test, an infinite-order ladder-type
resummation is analytically treated in the Kondo regime, recovering the correct
energy scale. An extension to the Anderson-lattice model is obtained via an
effective-site approximation through a cumulant expansion in on the
lattice. Relation to treatments in infinite spatial dimensions are indicated.Comment: selfextracting postscript file containing entire paper (10 pages)
including 3 figures, in case of trouble contact author for LaTeX-source or
hard copies (prep0994
Disentanglement of the electronic and lattice parts of the order parameter in a 1D Charge Density Wave system probed by femtosecond spectroscopy
We report on the high resolution studies of the temperature (T) dependence of
the q=0 phonon spectrum in the quasi one-dimensional charge density wave (CDW)
compound K0.3MoO3 utilizing time-resolved optical spectroscopy. Numerous modes
that appear below Tc show pronounced T-dependences of their amplitudes,
frequencies and dampings. Utilizing the time-dependent Ginzburg-Landau theory
we show that these modes result from linear coupling of the electronic part of
the order parameter to the 2kF phonons, while the (electronic) CDW amplitude
mode is overdamped.Comment: 4 pages, 3 figures + supplementary material, accepted for publication
in Phys. Rev. Let
Disorder Driven Critical Behavior of Periodic Elastic Media in a Crystal Potential
We study a lattice model of a three-dimensional periodic elastic medium at
zero temperature with exact combinatorial optimization methods. A competition
between pinning of the elastic medium, representing magnetic flux lines in the
mixed phase of a superconductor or charge density waves in a crystal, by
randomly distributed impurities and a periodic lattice potential gives rise to
a continuous phase transition from a flat phase to a rough phase. We determine
the critical exponents of this roughening transition via finite size scaling
obtaining , , and find
that they are universal with respect to the periodicity of the lattice
potential. The small order parameter exponent is reminiscent of the random
field Ising critical behavior in 3.Comment: 4 pages, 3 eps-figures include
Low-temperature laser-stimulated controllable generation of micro-bubbles in a water suspension of absorptive colloid particles
From Luttinger liquid to Altshuler-Aronov anomaly in multi-channel quantum wires
A crossover theory connecting Altshuler-Aronov electron-electron interaction
corrections and Luttinger liquid behavior in quasi-1D disordered conductors has
been formulated. Based on an interacting non-linear sigma model, we compute the
tunneling density of states and the interaction correction to the conductivity,
covering the full crossover.Comment: 15 pages, 3 figures, revised version, accepted by PR
Specific heat of the quantum Bragg Glass
We study the thermodynamics of the vibrational modes of a lattice pinned by
impurity disorder in the absence of topological defects (Bragg glass phase).
Using a replica variational method we compute the specific heat in the
quantum regime and find at low temperatures in dimension
three and two. The prefactor is controlled by the pinning length. The non
trivial cancellation of the linear term in arises from the so-called
marginality condition and has important consequences for other mean field
models.Comment: 5 pages, RevTex, strongly revised versio
On the driven Frenkel-Kontorova model: II. Chaotic sliding and nonequilibrium melting and freezing
The dynamical behavior of a weakly damped harmonic chain in a spatially
periodic potential (Frenkel-Kontorova model) under the subject of an external
force is investigated. We show that the chain can be in a spatio-temporally
chaotic state called fluid-sliding state. This is proven by calculating
correlation functions and Lyapunov spectra. An effective temperature is
attributed to the fluid-sliding state. Even though the velocity fluctuations
are Gaussian distributed, the fluid-sliding state is clearly not in equilibrium
because the equipartition theorem is violated. We also study the transition
between frozen states (stationary solutions) and=7F molten states
(fluid-sliding states). The transition is similar to a first-order phase
transition, and it shows hysteresis. The depinning-pinning transition
(freezing) is a nucleation process. The frozen state contains usually two
domains of different particle densities. The pinning-depinning transition
(melting) is caused by saddle-node bifurcations of the stationary states. It
depends on the history. Melting is accompanied by precursors, called
micro-slips, which reconfigurate the chain locally. Even though we investigate
the dynamics at zero temperature, the behavior of the Frenkel-Kontorova model
is qualitatively similar to the behavior of similar models at nonzero
temperature.Comment: Written in RevTeX, 13 figures in PostScript, appears in PR
Orbital rotation without orbital angular momentum: mechanical action of the spin part of the internal energy flow in light beams
It is known that internal energy flow in a light beam can be divided into the
orbital flow, associated with the macroscopic energy redistribution within the
beam, and the spin flow originating from instantaneous rotation of the field
vectors inherent in circular or elliptic polarization. In contrast to the
orbital one, experimental observation of the spin flow constituent seemed
problematic because (i) it does not manifest itself in the visible
transformation of the beam profile and (ii) it converts into the orbital flow
upon tight focusing of the beam, usually employed for the energy flow detection
by the mechanical action on probe particles. We propose a two-beam interference
technique that permits to obtain appreciable level of the spin flow in
moderately focused beams and to detect the orbital motion of probe particles
within a field where the transverse energy circulation is associated
exclusively with the spin flow. This result can be treated as the first
demonstration of mechanical action of the spin flow of a light field.Comment: 9 pages, 3 figures and 1 video cli
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