Quasiparticle vanishing driven by geometrical frustration

TL;DR

This paper explores how geometrical frustration in the triangular t-J model affects single hole dynamics, revealing conditions where quasiparticles vanish or persist, and highlighting the complex interplay of magnetic interactions.

Contribution

It demonstrates that geometrical frustration can break the conventional quasiparticle picture in the triangular t-J model, with detailed analysis of spectral functions and magnetic effects.

Findings

Quasiparticles vanish outside magnetic Goldstone modes for positive t.

Quasiparticles remain well-defined for negative t.

Resonances scale as (J/t)^2/3 and relate to string excitations.

Abstract

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 Neel 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 neighbourhood of the magnetic 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 between magnon-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.