335 research outputs found
Itinerant and localized magnetism on the triangular lattice: sodium rich phases of NaCoO
We study the interplay between correlation, itinerant ferromagnetism and
local moment formation on the electron doped triangular lattice of sodium
cobaltates NaCoO. We find that strong correlation renormalizes the
Stoner criterion and stabilizes the paramagnetic state for .
For , ferromagnetic (FM) order emerges. The enhanced Na dopant potential
fluctuations play a crucial role in the sodium rich phases and lead to an
inhomogeneous FM state, exhibiting nonmagnetic Co patches,
antiferromagnetic (AF) correlated regions, and FM clusters with AF domains.
Hole doping the band insulator at x=1 leads to the formation of local moments
near the Na vacancies and AF correlated magnetic clusters. We explain recent
observations by neutron, SR, and NMR experiments on the evolution of the
magnetic properties in the sodium rich phases.Comment: revtex4 file, 5 pages, 3 figures, published versio
Pseudogap, competing order and coexistence of staggered flux and d-wave pairing in high-temperature superconductors
We study the t-J-V model of a doped Mott insulator in connection to high-T_c
superconductors. The nearest neighbor Coulomb interaction (V) is treated
quantum mechanically on equal footing as the antiferromagnetic exchange
interaction (J). Motivated by the SU(2) symmetry at half-filling, we construct
a large-N theory which allows a systematic study of the interplay between
staggered flux order and superconductivity upon doping. We solve the model in
the large-N limit and obtain the ground state properties and the phase diagram
as a function of doping. We discuss the competition and the coexistence of the
staggered flux and the d-wave superconductivity in the underdoped regime and
the disappearance of superconductivity in the overdoped regimeComment: 5 pages, 3 figures, published versio
Chern Fermi pocket, topological pair density wave, and charge-4e and charge-6e superconductivity in kagome superconductors
The recent discovery of novel charge density wave (CDW) and pair density wave
(PDW) in kagom\'e lattice superconductors VSb ( K, Rb, Cs) hints
at unexpected time-reversal symmetry breaking correlated and topological states
whose physical origin and broader implications are not understood. Here, we
make conceptual advances toward a mechanism behind the striking observations
and new predictions for novel macroscopic phase coherent quantum states. We
show that the metallic CDW state with circulating loop currents is a doped
orbital Chern insulator near van Hove filling. The emergent Chern Fermi pockets
(CFPs) carry concentrated Berry curvature and orbital magnetic moment. We find
that the pairing of electrons on the CFPs leads to a superconducting state with
an emergent vortex-antivortex lattice and the formation of a complex
triple-\textbf{Q} PDW. A plethora of correlated and topological states emerge,
including a never-before-encountered chiral topological PDW superconductor, a
loop-current pseudogap phase, and vestigial charge-4 and charge-6
superconductivity in staged melting of the vortex-antivortex lattice and
hexatic liquid crystal. Our findings reveal previously unknown nature of the
superconducting state of a current-carrying Chern metal, with broad
implications for correlated and topological materials.Comment: 11 pages, 8 figures
Inhomogeneous states with checkerboard order in the t-J Model
We study inhomogeneous states in the t-J model using an unrestricted
Gutzwiller approximation. We find that checkerboard order, where
is a doping dependent number, emerges from Fermi surface instabilities of
both the staggered flux phase and the Fermi liquid state with realistic band
parameters. In both cases, the checkerboard order develops at wave vectors
, that are tied to the peaks of the
wave-vector dependent susceptibility, and is of the Lomer-Rice-Scott type. The
properties of such periodic, inhomogeneous states are discussed in connection
to the checkerboard patterns observed by STM in underdoped cuprates.Comment: Published Versio
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