2,044 research outputs found
Neel order, quantum spin liquids and quantum criticality in two dimensions
This paper is concerned with the possibility of a direct second order
transition out of a collinear Neel phase to a paramagnetic spin liquid in two
dimensional quantum antiferromagnets. Contrary to conventional wisdom, we show
that such second order quantum transitions can potentially occur to certain
spin liquid states popular in theories of the cuprates. We provide a theory of
this transition and study its universal properties in an expansion.
The existence of such a transition has a number of interesting implications for
spin liquid based approaches to the underdoped cuprates. In particular it
considerably clarifies existing ideas for incorporating antiferromagnetic long
range order into such a spin liquid based approach.Comment: 18 pages, 17 figure
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
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
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
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
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
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