Triangular antiferromagnet: bosonic spinons and kinetic antiferromagnetism

L. O. MANUEL

Los Alamos (New Mexico)

Seminario; Charla dictada en el grupo de Teoría de Materia Condensada de Los Alamos National Laboratory; 2010

Condensed Matter Theory Group, Los Alamos National Laboratory

We study two aspects of the triangular antiferromagnet. First, we show that the anomalous excitation spectrum of the spin 1/2 triangular Heisenberg model, recently found with series expansion, can be naturally interpreted in terms of bosonic spinon excitations using a Schwinger boson mean field theory. In particular, we find a qualitative and quantitative agreement of the strong renormalization of the high energy part of the spectrum with respect to spin wave results along with the appearance of roton like minima at the midpoints of faces of the hexagonal Brillouin zone. Second, we show that the ground state magnetic phase diagram of the triangular t-J model depends in a crucial way on the sign of the hopping integral t, due to the particle-hole asymmetry of the triangular lattice. For positive t, the motion of the doped holes gives rise to an enhancement of the 120° antiferromagnetic correlations present in the half-filled case. In particular, for small J/t we have found that an antiferromagnetic version of the Nagaoka phase is stabilized for a wide range of doping.