42,024 research outputs found
Spin-charge Separation in Nodal Antiferromagnetic Insulator
In this paper, by using two dimensional (2D) Hubbard models with pi-flux
phase and that on a hexagonal lattice as examples, we explore
spin-charge-separated solitons in nodal antiferromagnetic (AF) insulator - an
AF order with massive Dirac fermionic excitations (see detail in the paper). We
calculate fermion zero modes and induced quantum numbers on solitons (half
skyrmions) in the continuum limit, which are similar to that in the quasi
one-dimensional conductor polyacetylene (CH)x and that in topological band
insulator. In particular, we find some novel phenomena : thanks to an induced
staggered spin moment, a mobile half skyrmion becomes a fermionic particle;
when a hole or an electron is added, the half skyrmion turns into a bosonic
particle with charge degree of freedom only. Our results imply that nontrivial
induced quantum number on solitons may be a universal feature of spin-charge
separation in different systems
On length spectrum metrics and weak metrics on Teichmüller spaces of surfaces with boundary
We define and study metrics and weak metrics on the Teichmüller space of a surface of topologically finite type with boundary. These metrics and weak metrics are associated to the hyperbolic length spectrum of simple closed curves and of properly embedded arcs in the surface. We give a comparison between the defined metrics on regions of Teichmüller space which we call -relative -thick parts} for and
Transverse Quark Distribution in Mesons - QCD Sum Rule Approach -
QCD sum rules are used to compute the first few moments of the mesonic quark
momentum. Transverse, longitudinal and mixed transverse-longitudinal components
are examined. The transverse size of the pion is shown to be dictated by the
gluon condensate, even though the mass and the longitudinal distribution are
dominated by the quark condensate. The implications of our results for color
transparency physics and finite temperature QCD are discussed.Comment: 8 pages, Latex, Univ. of Washington preprint DOE/ER/40427-24-N9
Length spectra and the Teichmüller metric for surfaces with boundary
International audienceWe consider some metrics and weak metrics defined on the Teichmmüller space of a surface of finite type with nonempty boundary, that are defined using the hyperbolic length spectrum of simple closed curves and of properly embedded arcs, and we compare these metrics and weak metrics with the Teichmüller metric. The comparison is on subsets of Teichmüller space which we call ''-relative -thick parts", and whose definition depends on the choice of some positive constants and . Meanwhile, we give a formula for the Teichmüller metric of a surface with boundary in terms of extremal lengths of families of arcs
Transport Properties in the "Strange Metal Phase" of High Tc Cuprates: Spin-Charge Gauge Theory Versus Experiments
The SU(2)xU(1) Chern-Simons spin-charge gauge approach developed earlier to
describe the transport properties of the cuprate superconductors in the
``pseudogap'' regime, in particular, the metal-insulator crossover of the
in-plane resistivity, is generalized to the ``strange metal'' phase at higher
temperature/doping. The short-range antiferromagnetic order and the gauge field
fluctuations, which were the key ingredients in the theory for the pseudogap
phase, also play an important role in the present case. The main difference
between these two phases is caused by the existence of an underlying
statistical -flux lattice for charge carriers in the former case, whereas
the background flux is absent in the latter case. The Fermi surface then
changes from small ``arcs'' in the pseudogap to a rather large closed line in
the strange metal phase. As a consequence the celebrated linear in T dependence
of the in-plane and out-of-plane resistivity is shown explicitly to recover.
The doping concentration and temperature dependence of theoretically calculated
in-plane and out-of-plane resistivity, spin-relaxation rate and AC conductivity
are compared with experimental data, showing good agreement.Comment: 14 pages, 5 .eps figures, submitted to Phys. Rev. B, revised version
submitted on 24 Oc
Fulde-Ferrel-Larkin-Ovchinnikov Inhomogeneous Superconducting State and Phase Transitions Induced by Spin Accumulation in a Ferromagnet--Wave Superconductor-Ferromagnet Tunnel Junction
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting (SC)
state, first- and second-order phase transitions, and quantum criticality
induced by spin accumulation in a ferromagnet--wave
superconductor-ferromagnet tunnel junction are theoretically predicted. A
complex phase diagram in the temperature-bias voltage plane is determined. It
is found that the phase transitions from the homogeneous BCS state to the
inhomogeneous FFLO state, and from the FFLO state with the momentum 's azimuthal angle to that with , are of the first-order; while the transitions from all SC
states to the normal state at critical voltages are of the second-order. A
Lifshitz point, a bicritical point and a quantum critical point are identified.Comment: 5 pages, 5 figure
First- and Second-Order Phase Transitions, Fulde-Ferrel Inhomogeneous State and Quantum Criticality in Ferromagnet/Superconductor Double Tunnel Junctions
First- and second-order phase transitions, Fulde-Ferrel (FF) inhomogeneous
superconducting (SC) state and quantum criticality in
ferromagnet/superconductor/ferromagnet double tunnel junctions are
investigated. For the antiparallel alignment of magnetizations, it is shown
that a first-order phase transition from the homogeneous BCS state to the
inhomogeneous FF state occurs at a certain bias voltage ; while the
transitions from the BCS state and the FF state to the normal state at are of the second-order. A phase diagram for the central superconductor
is presented. In addition, a quantum critical point (QCP), , is
identified. It is uncovered that near the QCP, the SC gap, the chemical
potential shift induced by the spin accumulation, and the difference of free
energies between the SC and normal states vanish as with
the quantum critical exponents , 1 and 2, respectively. The tunnel
conductance and magnetoresistance are also discussed.Comment: 5 pages, 4 figures, Phys. Rev. B 71, 144514 (2005
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