Systematic effective field theory investigation of spiral phases in hole-doped antiferromagnets on the honeycomb lattice

• Published in: The European physical journal. B, Condensed matter physics Vol. 69; no. 4; pp. 473 - 482
• Main Authors: Jiang, F.-J., Kämpfer, F., Hofmann, C. P., Wiese, U.-J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2009; EDP Sciences
• Subjects: Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fluid- and Aerodynamics; Magnetic properties; Physics; Physics and Astronomy; Properties of type I and type II superconductors; Solid State and Materials; Solid State Physics; Superconductivity; resonating valence bond model; spin fluctuations; 74.20.Mn Nonconventional mechanisms; 12.39.Fe Chiral Lagrangians; marginal Fermi liquid; 75.50.Ee Antiferromagnetics; polarons and bipolarons; anyon mechanism; Luttinger liquid, etc; 75.30.Ds Spin waves; Effective field approximation; Honeycomb lattices; Magnetization; Hole density; Doping; Antiferromagnetic materials; Low field; Spiral structure; High-Tc superconductors; Helical structure; Cobalt Sodium Oxides Mixed; Square lattices; Magnons; Hydrates
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2009-00200-x

Motivated by possible applications to the antiferromagnetic precursor of the high-temperature superconductor Na x CoO 2 .yH 2 O, we use a systematic low-energy effective field theory for magnons and holes to study different phases of doped antiferromagnets on the honeycomb lattice. The effective action contains a leading single-derivative term, similar to the Shraiman-Siggia term in the square lattice case, which gives rise to spirals in the staggered magnetization. Depending on the values of the low-energy parameters, either a homogeneous phase with four or a spiral phase with two filled hole pockets is energetically favored. Unlike in the square lattice case, at leading order the effective action has an accidental continuous spatial rotation symmetry. Consequently, the spiral may point in any direction and is not necessarily aligned with a lattice direction.