53 research outputs found
Magnetic and Ising quantum phase transitions in a model for isoelectronically tuned iron pnictides
Considerations of the bad-metal behavior led to an early proposal for a
quantum critical point under a P for As doping in the iron pnictides, which has
since been experimentally observed. We study here an effective model for the
isoelectronically tuned pnictides using a large- approach. The model
contains antiferromagnetic and Ising-nematic order parameters appropriate for
- exchange-coupled local moments on an Fe square lattice, and a
damping caused by coherent itinerant electrons. The zero-temperature magnetic
and Ising transitions are concurrent and essentially continuous. The
order-parameter jumps are very small, and are further reduced by the
inter-plane coupling; quantum criticality hence occurs over a wide dynamical
range. Our results provide the basis for further studies on the quantum
critical properties in the P-doped iron arsenides.Comment: 5 pages 2 figures - Supplementary Material 9 pages 4 figure
Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides
We consider the iron pnictides in terms of a proximity to a Mott insulator.
The superexchange interactions contain competing nearest-neighbor and
next-nearest-neighbor components. In the undoped parent compound, these
frustrated interactions lead to a two-sublattice collinear antiferromagnet
(each sublattice forming a Neel ordering), with a reduced magnitude for the
ordered moment. Electron or hole doping, together with the frustration effect,
suppresses the magnetic ordering and allows a superconducting state. The
exchange interactions favor a d-wave superconducting order parameter; in the
notation appropriate for the Fe square lattice, its orbital symmetry is
. A number of existing and future experiments are discussed in light of
the theoretical considerations.Comment: (v2) 4+ pages, 4 figures, discussions on several points expanded;
references added. To appear in Phys. Rev. Let
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