706 research outputs found
Charge-density-wave formation in the Edwards fermion-boson model at one-third band filling
We examine the ground-state properties of the one-dimensional Edwards
spinless fermion transport model by means of large-scale density-matrix
renormalization-group calculations. Determining the single-particle gap and the
Tomonaga-Luttinger liquid parameter () at zero temperature, we prove
the existence of a metal-to-insulator quantum phase transition at one-third
band filling. The insulator---established by strong correlation in the
background medium---typifies a charge density wave (CDW) that is commensurate
with the band filling. is very small at the quantum critical
point, and becomes in the infinitesimally doped
three-period CDW, as predicted by the bosonization approach.Comment: 6 pages, 3 figures, contributions to SCES 201
The Mixed State of Charge-Density-Wave in a Ring-Shaped Single Crystals
Charge-density-wave (CDW) phase transition in a ring-shaped crystals,
recently synthesized by Tanda et al. [Nature, 417, 397 (2002)], is studied
based on a mean-field-approximation of Ginzburg-Landau free energy. It is shown
that in a ring-shaped crystals CDW undergoes frustration due to the curvature
(bending) of the ring (geometrical frustration) and, thus, forms a mixed state
analogous to what a type-II superconductor forms under a magnetic field. We
discuss the nature of the phase transition in the ring-CDW in relation to
recent experiments.Comment: 6 pages, 4 figure
Spin-Peierls Quantum Phase Transitions in Coulomb Crystals
The spin-Peierls instability describes a structural transition of a crystal
due to strong magnetic interactions. Here we demonstrate that cold Coulomb
crystals of trapped ions provide an experimental testbed in which to study this
complex many-body problem and to access extreme regimes where the instability
is triggered by quantum fluctuations alone. We present a consistent analysis
based on different analytical and numerical methods, and provide a detailed
discussion of its feasibility on the basis of ion-trap experiments. Moreover,
we identify regimes where this quantum simulation may exceed the power of
classical computers.Comment: slightly longer than the published versio
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
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
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
Peierls instability, periodic Bose-Einstein condensates and density waves in quasi-one-dimensional boson-fermion mixtures of atomic gases
We study the quasi-one-dimensional (Q1D) spin-polarized bose-fermi mixture of
atomic gases at zero temperature. Bosonic excitation spectra are calculated in
random phase approximation on the ground state with the uniform BEC, and the
Peierls instabilities are shown to appear in bosonic collective excitation
modes with wave-number by the coupling between the Bogoliubov-phonon
mode of bosonic atoms and the fermion particle-hole excitations. The
ground-state properties are calculated in the variational method, and,
corresponding to the Peierls instability, the state with a periodic BEC and
fermionic density waves with the period are shown to have a lower
energy than the uniform one. We also briefly discuss the Q1D system confined in
a harmonic oscillator (HO) potential and derive the Peierls instability
condition for it.Comment: 9 pages, 3figure
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