2,093 research outputs found
Vertical and Diagonal Stripes in the Extended Hubbard Model
We extend previous real-space Hartree-Fock studies of static stripe stability
to determine the phase diagram of the Hubbard model with anisotropic
nearest-neighbor hopping t, by varying the on-site Coulomb repulsion U and
investigating locally stable structures for representative hole doping levels
x=1/8 and x=1/6. We also report the changes in stability of these stripes in
the extended Hubbard model due to next-neighbor hopping t' and to a
nearest-neighbor Coulomb interaction V.Comment: 4 pages, 2 figure
Planckian dissipation, minimal viscosity and the transport in cuprate strange metals
Could it be that the matter from the electrons in high Tc superconductors is
of a radically new kind that may be called "many body entangled compressible
quantum matter"? Much of this text is intended as an easy to read tutorial,
explaining recent theoretical advances that have been unfolding at the cross
roads of condensed matter- and string theory, black hole physics as well as
quantum information theory. These developments suggest that the physics of such
matter may be governed by surprisingly simple principles. My real objective is
to present an experimental strategy to test critically whether these principles
are actually at work, revolving around the famous linear resistivity
characterizing the strange metal phase. The theory suggests a very simple
explanation of this "unreasonably simple" behavior that is actually directly
linked to remarkable results from the study of the quark gluon plasma formed at
the heavy ion colliders: the "fast hydrodynamization" and the "minimal
viscosity". This leads to high quality predictions for experiment: the momentum
relaxation rate governing the resistivity relates directly to the electronic
entropy, while at low temperatures the electron fluid should become unviscous
to a degree that turbulent flows can develop even on the nanometre scale.Comment: 23 pages, no figures. Submission to SciPos
Stripe fractionalization II: the quantum spin nematic and the Abrikosov lattice
In part (I) of this two paper series on stripe fractionalization, we argued
that in principle the `domain wall-ness' of the stripe phase could persist in
the spin and charge disordered superconductors, and we demonstrated how this
physics is in one-to-one correspondence with Ising gauge theory. Here we focus
on yet another type of order suggested by the gauge theory: the quantum spin
nematic. Although it is not easy to measure this order directly, we argue that
the superconducting vortices act as perturbations destroying the gauge symmetry
locally. This turns out to give rise to a simple example of a gauge-theoretical
phenomenon known as topological interaction. As a consequence, at any finite
vortex density a globally ordered antiferromagnet emerges. This offers a
potential explanation for recent observations in the underdoped 214 system
Half-filled stripes in the t-t'-U Hubbard model
Using a self-consistent Hartree-Fock approximation we investigate the
relative stability of various stripe phases in the extended --
Hubbard model. One finds that a negative ratio of next- to nearest-neighbor
hopping expells holes from antiferromagnetic domains and reinforces
the stripe order. Therefore the half-filled stripes not only accommodate holes
but also redistribute them so that the kinetic energy is gained, and these
stripes take over in the regime of appropriate for
YBaCuO.Comment: Accepted for publication in Phys. Stat. So
Dynamical stripe correlations and the spin fluctuations in cuprate superconductors
It is conjectured that the anomalous spin dynamics observed in the normal
state of cuprate superconductors might find its origin in a nearly ordered spin
system which is kept in motion by thermally meandering charged domain walls.
`Temperature sets the scale' finds a natural explanation, while a crossover to
a low temperature quantum domain wall fluid is implied.Comment: 3 pages Revtex. To appear in Physica
Stripe fractionalization I: the generation of Ising local symmetry
This is part one in a series of two papers dedicated to the notion that the
destruction of the topological order associated with stripe phases is about the
simplest theory controlled by local symmetry: Ising gauge theory. This first
part is intended to be a tutorial- we will exploit the simple physics of the
stripes to vividly display the mathematical beauty of the gauge theory.
Stripes, as they occur in the cuprates, are clearly `topological' in the sense
that the lines of charges are at the same time domain walls in the
antiferromagnet. Imagine that the stripes quantum melt so that all what seems
to be around is a singlet superconductor. What if this domain wall-ness is
still around in a delocalized form? This turns out to be exactly the kind of
`matter' which is described by the Ising gauge theory. The highlight of the
theory is the confinement phenomenon, meaning that when the domain wall-ness
gives up it will do so in a meat-and-potato phase transition. We suggest that
this transition might be the one responsible for the quantum criticality in the
cuprates. In part two, we will become more practical, arguing that another
phase is possible according to the theory. It might be that this quantum
spin-nematic has already been observed in strongly underdoped LSCO
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