Quasiparticle vanishing driven by geometrical frustration

TRUMPER, ADOLFO E.; GAZZA, CLAUDIO J.; L. O. MANUEL

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Lugar: New York; Año: 2004 vol. 69 p. 84407 - 84407

0163-1829

We investigate the single hole dynamics in the triangular t-J model. We study the structure of the hole spectral function, assuming the existence of a 120° magnetic Ne´el order. Within the self-consistent Born approximation (SCBA) there is a strong momentum and t sign dependence of the spectra, related to the underlying magnetic structure and the particle-hole asymmetry of the model. For positive t, and in the strong coupling regime, we find that the low-energy quasiparticle excitations vanish outside the neighborhood of themagnetic Goldstone modes; while for negative t the quasiparticle excitations are always well defined. In the latter, we also find resonances of magnetic origin whose energies scale as (J/t)^2/3 and can be identified with string excitations. We argue that this complex structure of the spectra is due to the subtle interplay betweenmagnon-assisted and free-hopping mechanisms. Our predictions are supported by an excellent agreement between the SCBA and the exact results on finite-size clusters. We conclude that the conventional quasiparticle picture can be broken by the effect of geometrical magnetic frustration.