5,201 research outputs found
Understanding high-Tc cuprates based on the phase string theory of doped antiferromagnet
We present a self-consistent RVB theory which unifies the metallic
(superconducting) phase with the half-filling antiferromagnetic (AF) phase. Two
crucial factors in this theory include the RVB condensation which controls
short-range AF spin correlations and the phase string effect introduced by hole
hopping as a key doping effect. We discuss both the uniform and non-uniform
mean-field solutions and show the unique features of the characteristic spin
energy scale, superconducting transition temperature, and the phase diagram,
which are all consistent with the experimental measurements of high-
cuprates.Comment: 4 pages, 4 embeded eps figures, minor typos are corrected, to appear
in the proceedings of M2S-HTSC-VI conferenc
Mutual Chern-Simons Theory of Spontaneous Vortex Phase
We apply the mutual Chern-Simons effective theory (Phys. Rev. B 71, 235102)
of the doped Mott insulator to the study of the so-called spontaneous vortex
phase in the low-temperature pseudogap region, which is characterized by strong
unconventional superconducting fluctuations. An effective description for the
spontaneous vortex phase is derived from the general mutual Chern-Simons
Lagrangian, based on which the physical properties including the diamagnetism,
spin paramagnetism, magneto-resistance, and the Nernst coefficient, have been
quantitatively calculated. The phase boundaries of the spontaneous vortex phase
which sits between the onset temperature and the superconducting
transition temperature , are also determined within the same framework.
The results are consistent with the experimental measurements of the cuprates.Comment: 12 pages, 8 figure
The electronic structure of NaIrO, Mott insulator or band insulator?
Motivated by the unveiled complexity of nonmagnetic insulating behavior in
pentavalent post-perovskite NaIrO, we have studied its electronic structure
and phase diagram in the plane of Coulomb repulsive interaction and spin-orbit
coupling (SOC) by using the newly developed local density approximation plus
Gutzwiller method. Our theoretical study proposes the metal-insulator
transition can be generated by two different physical pictures: renormalized
band insulator or Mott insulator regime. For the realistic material parameters
in NaIrO, Coulomb interaction eV and SOC strength
eV, it tends to favor the renormalized band insulator picture as
revealed by our study.Comment: 5 pages, 4 figure
Non-collinear magnetic structure and multipolar order in EuIrO
The magnetic properties of the pyrochlore iridate material EuIrO
(5) have been studied based on the first principle calculations, where the
crystal field splitting , spin-orbit coupling (SOC) and
Coulomb interaction within Ir 5 orbitals are all playing significant
roles. The ground state phase diagram has been obtained with respect to the
strength of SOC and Coulomb interaction , where a stable anti-ferromagnetic
ground state with all-in/all-out (AIAO) spin structure has been found. Besides,
another anti-ferromagnetic states with close energy to AIAO have also been
found to be stable. The calculated nonlinear magnetization of the two stable
states both have the d-wave pattern but with a phase difference, which
can perfectly explain the experimentally observed nonlinear magnetization
pattern. Compared with the results of the non-distorted structure, it turns out
that the trigonal lattice distortion is crucial for stabilizing the AIAO state
in EuIrO. Furthermore, besides large dipolar moments, we also find
considerable octupolar moments in the magnetic states.Comment: 6 pages, 4 figures, supplemental material is included in the source
file, accepted for publication in PR
Lower Pseudogap Phase: A Spin/Vortex Liquid State
The pseudogap phase is considered as a new state of matter in the phase
string model of the doped Mott insulator, which is composed of two distinct
regimes known as upper and lower pseudogap phases, respectively. The former
corresponds to the formation of spin singlet pairing and the latter is
characterized by the formation of the Cooper pair amplitude and described by a
generalized Gingzburg-Landau theory. Elementary excitation in this phase is a
charge-neutral object carrying spin-1/2 and locking with a supercurrent vortex,
known as spinon-vortex composite. Here thermally excited spinon-vortices
destroy the phase coherence and are responsible for nontrivial Nernst effect
and diamagnetism. The transport entropy and core energy associated with a
spinon-vortex are determined by the spin degrees of freedom. Such a spontaneous
vortex liquid phase can be also considered as a spin liquid with a finite
correlation length and gapped S=1/2 excitations, where a resonancelike
non-propagating spin mode emerges at the antiferromagnetic wavevector with a
doping-dependent characteristic energy. A quantitative phase diagram in the
parameter space of doping, temperature, and magnetic field is determined.
Comparisons with experiments are also made.Comment: 22 pages, 12 figure
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