34,603 research outputs found
Luttinger Stripes in Antiferromagnets
We propose a model for the physics of stripes in antiferromagnets in which
the stripes are described by Luttinger liquids hybridized with
antiferromagnetic domains. Using bosonization techniques we study the model in
the limit where the magnetic correlation length is larger than the inter-stripe
distance and propose an explanation for the commensurate-incommensurate phase
transition seen in neutron scattering in the underdoped regime of La_{2-x} Sr_x
Cu O_4. The explanation is based on a phase to anti-phase domain transition in
the spin configuration which is associated with the transverse motion of the
stripes. Using a non-linear sigma model to describe the antiferromagnetic
regions we conjecture the crystalization of the stripes in the magnetically
ordered phase.Comment: 9 pages, Revtex, Epsf, 4 figures. To appear in the Proceedings of the
Euroconference on "Correlations in unconventional quantum liquids" in
Zeitschrift f\"ur Physik B - Condensed Matter (dedicated to the memory of Sir
Rudolph Peierls
Conductivity of suspended and non-suspended graphene at finite gate voltage
We compute the DC and the optical conductivity of graphene for finite values
of the chemical potential by taking into account the effect of disorder, due to
mid-gap states (unitary scatterers) and charged impurities, and the effect of
both optical and acoustic phonons. The disorder due to mid-gap states is
treated in the coherent potential approximation (CPA, a self-consistent
approach based on the Dyson equation), whereas that due to charged impurities
is also treated via the Dyson equation, with the self-energy computed using
second order perturbation theory. The effect of the phonons is also included
via the Dyson equation, with the self energy computed using first order
perturbation theory. The self-energy due to phonons is computed both using the
bare electronic Green's function and the full electronic Green's function,
although we show that the effect of disorder on the phonon-propagator is
negligible. Our results are in qualitative agreement with recent experiments.
Quantitative agreement could be obtained if one assumes water molelcules under
the graphene substrate. We also comment on the electron-hole asymmetry observed
in the DC conductivity of suspended graphene.Comment: 13 pages, 11 figure
Roughness correction to the Casimir force : Beyond the Proximity Force Approximation
We calculate the roughness correction to the Casimir effect in the parallel
plates geometry for metallic plates described by the plasma model. The
calculation is perturbative in the roughness amplitude with arbitrary values
for the plasma wavelength, the plate separation and the roughness correlation
length. The correction is found to be always larger than the result obtained in
the Proximity Force Approximation.Comment: 7 pages, 3 figures, v2 with minor change
Metallic Continuum Quantum Ferromagnets at Finite Temperature
We study via renormalization group (RG) and large N methods the problem of
continuum SU(N) quantum Heisenberg ferromagnets (QHF) coupled to gapless
electrons. We establish the phase diagram of the dissipative problem and
investigate the changes in the Curie temperature, magnetization, and magnetic
correlation length due to dissipation and both thermal and quantum
fluctuations. We show that the interplay between the topological term (Berry's
phase) and dissipation leads to non-trivial effects for the finite temperature
critical behavior.Comment: Corrected typos, new discussion of T=0 results, to appear in
Europhys. Let
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