10,867 research outputs found
Variational study of the one dimensional t-J model
We find the Gutzwiller projected Fermi sea wave function(GWF) has the correct
phase structure to describe the kink nature of the doped holes in the ground
state of the one dimensional model. We find the failure of the GWF for
general value of and electron density can be attributed to the
residual charge correlation in the ground state. We find such residual charge
correlation is well described by a XXZ-type effective Hamiltonian. Based on
these observations, a Pfaffian-type variational wave function is proposed and
is found to reproduce correctly the global phase diagram and corresponding
correlation functions of the one dimensional model, including the
Luther-Emery phase in the low electron density and large region.Comment: 8 pages, 8 figure
Spin Charge Recombination in Projected Wave Functions
We find spin charge recombination is a generic feature of projected wave
functions. We find this effect is responsible for a series of differences
between mean field theory prediction and the result from projected wave
functions. We also find spin charge recombination plays an important role in
determining the dissipation of supercurrent, the quasiparticle properties and
the hole - hole correlation.Comment: 13 pages,7 figure
Topological Order in Projected Wave Functions and Effective Theories of Quantum Antiferromagnets
We study the topological order in RVB state derived from Gutzwiller
projection of BCS-like mean field state. We propose to construct the
topological excitation on the projected RVB state through Gutzwiller projection
of mean field state with inserted flux tube. We prove that all
projected RVB states derived from bipartite effective theories, no matter the
gauge structure in the mean field ansatz, are positive definite in the sense of
the Marshall sign rule, which provides a universal origin for the absence of
topological order in such RVB state.Comment: 5 pages, 1 figure
The Hellberg-Mele Jastrow factor as a variational wave function for the one dimensional XXZ model
We find the Jastrow factor introduced by Hellberg and Mele in their study of
the one dimensional t-J model provides an exceedingly good variational
description of the one dimensional XXZ model.Comment: 3 pages, 2 figure
On the Origin of the Tunneling Asymmetry in the Cuprate Superconductors: a variational perspective
Through variational Monte Carlo calculation on Gutzwiller projected wave
functions, we study the quasiparticle(qp) weight for adding and removing an
electron from a high temperature superconductor. We find the qp weight is
particle-hole symmetric at sufficiently low energy. We propose to use the
tunneling asymmetry as a tool to study the mechanism of electron incoherence in
high temperature superconductors.Comment: 5 pages, 4figure
Influence of a uniform magnetic field on dynamical chiral symmetry breaking in QED
We study dynamical chiral symmetry breaking (DCSB) in an effective QED
theory of d-wave high temperature cuprate superconductors under a uniform
magnetic field. At zero temperature, the external magnetic field induces a
mixed state by generating vortices in the condensate of charged holons. The
growing magnetic field suppresses the superfluid density and thus reduces the
gauge field mass which is opened via the Anderson-Higgs mechanism. By
numerically solving the Dyson-Schwinger gap equation, we show that the massless
fermions acquires a dynamical gap through DCSB mechanism when the magnetic
field strength is above a critical value and the fermion flavors
is below a critical value . Further, it is found that both
and the dynamical fermion gap increase as the magnetic field grows. It is
expected that our result can be tested in phenomena in high temperature cuprate
superconductors.Comment: 12 pages, 2 figure
Calculation of the staggered spin correlation in the framework of the Dyson-Schwinger approach
Based on the linear response of the fermion propagator with respect to an
external field, we first derive a model-independent expression for the
staggered spin susceptibility in which the influence of the full pseudoscalar
vertex function is included. This expression for the staggered spin
susceptibility is quite different from that given in the previous literature.
The numerical values of the staggered spin susceptibility are calculated within
the framework of the Dyson-Schwinger approach. Our numerical result shows that
the nonperturbative dressing effects on the fermion propagator is very
important when one studies the staggered spin susceptibility which
corresponding to antiferromagnetic correlation in both Nambu phase and Winger
phase.Comment: 12 pages, 4 figure
Kondo spin liquid in Kondo necklace model: Classical disordered phase versus symmetry-protected topological state
We study possible topological features of Kondo spin liquid phase in terms of
the one- and two-dimensional Kondo necklace models within the frame work of
quantum O(N) non-liner sigma model (NLSM). In the one-dimensional case, it is
found that the bulk properties of the Kodno spin liquid phase are similar to
the well-known Haldane phase at strong coupling fixed point. The difference
between them mainly comes from their boundaries due to the effect of the
topological term. In the two-dimensional case, the system can be mapped onto an
O(4)-like NLSM with some O(3) anisotropy. Interestingly, we find that if
hedgehog-like point defects are included together with the restoration of the
full O(4) symmetry, our model is identical to a kind of SU(2)
symmetry-protected topological (SPT) state. Additionally, if the system has the
O(5) symmetry instead, the effective NLSM with Wess-Zumino-Witten term is just
a description of the surface modes of a three-dimensional SPT state, though
such O(5) NLSM could not be a proper description of Kondo spin liquid phase due
to its gaplessness. We expect that the discussions might provide useful threads
to identify certain microscopic bilayer antiferromagnet models (and related
materials), which can support the desirable SPT states.Comment: 8pages,3 figures, we have added an coauthor with achknowledgement
updated. This version is heavily revise
Topological quantum phase transition in Kane-Mele-Kondo lattice model
We systematically explore the ground-state phase diagram of the
Kane-Mele-Kondo lattice model on the honeycomb lattice, in particular, we focus
on its magnetic properties which has not been studied in the previous
publication[Feng, Dai, Chung, and Si, Phys. Rev. Lett. \textbf{111}, 016402
(2013)]. Beside the Kondo insulator found in that paper, two kinds of
antiferromagnetic spin-density-wave phases are identified. One is the normal
antiferromagnetic spin-density-wave state and the other is a nontrivial
topological antiferromagnetic spin-density-wave state with a quantized spin
Hall conductance and a helical edge-state. The quantum spin Hall insulator is
found to be absent since it is always unstable to antiferromagnetic
spin-density-wave states at least at the mean-field level in our model.
Furthermore, the transition between the two spin-density-wave phases are
topological quantum phase transition described by the three-dimensional quantum
electrodynamics, in which conduction electrons contribute to the low-energy
Dirac fermions while the spin-wave fluctuation of local spins gives rise to an
effective dynamic U(1) gauge-field. Such nontrivial transition shows radical
critical thermodynamic, transport and single-particle behaviors, which provide
a fingerprint for this transition. Additionally, the transition of
antiferromagnetic spin-density-wave states to the Kondo insulator is found to
be first-order. The introduction of two novel magnetic phases and their
topological quantum phase transition show rich and intrinsic physics involving
in the Kane-Mele-Kondo lattice model.Comment: 17 pages,5 figure
The Affine Hidden Symmetry and Integrability of Type IIB Superstring in
In this paper, we motivate how the Hodge dual related with S-duality gives
the hidden symmetry in the moduli space of IIB string. Utilizing the static -symmetric Killing gauge, if we take the Hodge dual of the vierbeins
keeping the connection invariant, the duality of Maure-Cartan equations and the
equations of motion becomes manifest. Thus by twistly transforming the
vierbein, we can express the BPR currents as the Lax connections by a unique
spectral parameter. Then we construct the generators of the infinitesimal
dressing symmetry, the related symmetric algebra becomes the affine , which can be used to find the classical matrix.Comment: 16 pages, no figures,typo crrected and references adde
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