2,620 research outputs found
Coherence and pairing in a doped Mott insulator: Application to the cuprates
The issues of single particle coherence and its interplay with singlet
pairing are studied within the slave boson gauge theory of a doped Mott
insulator. Prior work by one of us (T. Senthil, arXiv:0804.1555) showed that
the coherence scale below which Landau quasiparticles emerge is parametrically
lower than that identified in the slave boson mean field theory. Here we study
the resulting new non-fermi liquid intermediate temperature regime
characterized by a single particle scattering rate that is linear in
temperature (). In the presence of a d-wave pair amplitude this leads to a
pseudogap state with dependent Fermi arcs near the nodal direction.
Implications for understanding the cuprates are discussed.Comment: 4+ pages, 1 figure. Sequel to arXiv:0903.087
Design and Analysis of SD_DWCA - A Mobility based clustering of Homogeneous MANETs
This paper deals with the design and analysis of the distributed weighted
clustering algorithm SD_DWCA proposed for homogeneous mobile ad hoc networks.
It is a connectivity, mobility and energy based clustering algorithm which is
suitable for scalable ad hoc networks. The algorithm uses a new graph parameter
called strong degree defined based on the quality of neighbours of a node. The
parameters are so chosen to ensure high connectivity, cluster stability and
energy efficient communication among nodes of high dynamic nature. This paper
also includes the experimental results of the algorithm implemented using the
network simulator NS2. The experimental results show that the algorithm is
suitable for high speed networks and generate stable clusters with less
maintenance overhead
Fractionalization and confinement in the U(1) and gauge theories of strongly correlated systems
Recently, we have elucidated the physics of electron fractionalization in
strongly interacting electron systems using a gauge theory formulation.
Here we discuss the connection with the earlier U(1) gauge theory approaches
based on the slave boson mean field theory. In particular, we identify the
relationship between the holons and Spinons of the slave-boson theory and the
true physical excitations of the fractionalized phases that are readily
described in the approach.Comment: 4 page
Entanglement Structure of Deconfined Quantum Critical Points
We study the entanglement properties of deconfined quantum critical points.
We show not only that these critical points may be distinguished by their
entanglement structure but also that they are in general more highly entangled
that conventional critical points. We primarily focus on computations of the
entanglement entropy of deconfined critical points in 2+1 dimensions, drawing
connections to topological entanglement entropy and a recent conjecture on the
monotonicity under RG flow of universal terms in the entanglement entropy. We
also consider in some detail a variety of issues surrounding the extraction of
universal terms in the entanglement entropy. Finally, we compare some of our
results to recent numerical simulations.Comment: 12 pages, 4 figure
Overscreened Kondo fixed point in S=1 spin liquid
We propose a possible realization of the overscreened Kondo impurity problem
by a magnetic s=1/2 impurity embedded in a two-dimensional S=1 U(1) spin liquid
with a Fermi surface. This problem contains an interesting interplay between
non-Fermi-liquid behavior induced by a U(1) gauge field coupled to fermions and
a non-Fermi-liquid fixed point in the overscreened Kondo problem. Using a
large-N expansion together with an expansion in the dynamical exponent of the
gauge field, we find that the coupling to the gauge field leads to weak but
observable changes in the physical properties of the system at the overscreened
Kondo fixed point. We discuss the extrapolation of this result to a physical
case and argue that the realization of overscreened Kondo physics could lead to
observations of effects due to gauge fields.Comment: 10 pages, 5 figure
Cuprates as doped U(1) spin liquids
We explore theoretically the notion that the underdoped cuprates may be
viewed as doped U(1) spin liquid Mott insulators. We pursue a conceptually
clear version of this idea that naturally incorporates several aspects of the
phenomenology of the cuprates. We argue that the low doping region may be
fruitfully discussed in terms of the universal physics associated with a
chemical potential tuned Mott transition between a U(1) spin liquid insulator
and a d-wave superconductor. A precise characterization of the deconfinement in
the U(1) spin liquid is provided by the emergence of a conserved gauge flux.
This extra conservation law should hold at least approximately in the
underdoped materials. Experiments that could possibly detect this conserved
gauge flux are proposed.Comment: 11 pages, 7 figure
Spin nematics and magnetization plateau transition in anisotropic Kagome magnets
We study S=1 kagome antiferromagnets with isotropic Heisenberg exchange
and strong easy axis single-ion anisotropy . For , the low-energy
physics can be described by an effective model with
antiferromagnetic and ferromagnetic .
Exploiting this connection, we argue that non-trivial ordering into a
"spin-nematic" occurs whenever dominates over , and discuss its
experimental signatures. We also study a magnetic field induced transition to a
magnetization plateau state at magnetization 1/3 which breaks lattice
translation symmetry due to ordering of the and occupies a lobe in the
- phase diagram.Comment: 4pages, two-column format, three .eps figure
Symmetry classes of disordered fermions
Building upon Dyson's fundamental 1962 article known in random-matrix theory
as 'the threefold way', we classify disordered fermion systems with quadratic
Hamiltonians by their unitary and antiunitary symmetries. Important examples
are afforded by noninteracting quasiparticles in disordered metals and
superconductors, and by relativistic fermions in random gauge field
backgrounds.
The primary data of the classification are a Nambu space of fermionic field
operators which carry a representation of some symmetry group. Our approach is
to eliminate all of the unitary symmetries from the picture by transferring to
an irreducible block of equivariant homomorphisms. After reduction, the block
data specifying a linear space of symmetry-compatible Hamiltonians consist of a
basic vector space V, a space of endomorphisms in End(V+V*), a bilinear form on
V+V* which is either symmetric or alternating, and one or two antiunitary
symmetries that may mix V with V*. Every such set of block data is shown to
determine an irreducible classical compact symmetric space. Conversely, every
irreducible classical compact symmetric space occurs in this way.
This proves the correspondence between symmetry classes and symmetric spaces
conjectured some time ago.Comment: 52 pages, dedicated to Freeman J. Dyson on the occasion of his 80th
birthda
Erratum: algebraic spin liquid as the mother of many competing orders
We correct an error in our paper Phys. Rev. B 72, 104404 (2005)
[cond-mat/0502215]. We show that a particular fermion bilinear is not related
to the other ``competing orders'' of the algebraic spin liquid, and does not
possess their slowly decaying correlations. For the square lattice staggered
flux spin liquid (equivalently, d-wave RVB state), this observable corresponds
to the uniform spin chirality.Comment: 1.25 page
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