10,215 research outputs found
Hidden unity in the quantum description of matter
We introduce an algebraic framework for interacting quantum systems that
enables studying complex phenomena, characterized by the coexistence and
competition of various broken symmetry states of matter. The approach unveils
the hidden unity behind seemingly unrelated physical phenomena, thus
establishing exact connections between them. This leads to the fundamental
concept of {\it universality} of physical phenomena, a general concept not
restricted to the domain of critical behavior. Key to our framework is the
concept of {\it languages} and the construction of {\it dictionaries} relating
them.Comment: 10 pages 2 psfigures. Appeared in Recent Progress in Many-Body
Theorie
Field Induced Supersolid Phase in Spin-One Heisenberg Models
We use quantum Monte Carlo methods to demonstrate that the quantum phase
diagram of the S=1 Heisenberg model with uniaxial anisotropy contains an
extended supersolid phase. We also show that this Hamiltonian is a particular
case of a more general and ubiquitous model that describes the low energy
spectrum of a class of {\it isotropic} and {\it frustrated} spin systems. This
crucial result provides the required guidance for finding experimental
realizations of a spin supersolid state.Comment: 4 pages, 4 figure
Superconductivity and incommensurate spin fluctuations in a generalized t-J model for the cuprates
We consider the slave-fermion Schwinger-boson decomposition of an effective
model obtained through a systematic low-energy reduction of the three-band
Hubbard Hamiltonian. The model includes a three-site term t'' similar to that
obtained in the large-U limit of the Hubbard model but of opposite sign for
realistic or large O-O hopping. For parameters close to the most realistic ones
for the cuprates, the mean-field solution exhibits d+s superconductivity
(predominantly d_{x^2-y^2}) with a dependence on doping x very similar to the
experimentally observed. We also obtained incommensurate peaks at wave vectors
near in the spin structure factor, which also agree with
experiment.Comment: 9 pages, latex, 2 figures, to appear in Europhys. Let
Antiferromagnetic Order in Pauli Limited Unconventional Superconductors
We develop a theory of the coexistence of superconductivity (SC) and
antiferromagnetism (AFM) in CeCoIn5. We show that in Pauli-limited nodal
superconductors the nesting of the quasi-particle pockets induced by Zeeman
pair-breaking leads to incommensurate AFM with the moment normal to the field.
We compute the phase diagram and find a first order transition to the normal
state at low temperatures, absence of normal state AFM, and coexistence of SC
and AFM at high fields, in agreement with experiments. We also predict the
existence of a new double-Q magnetic phase
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