Exact-Diagonalization Analysis of Composite Excitations in the t-J Model

TL;DR

This paper uses exact diagonalization to analyze composite excitations in the t-J model, revealing their role in spectral features, localization, and pseudogap formation in high-Tc cuprates.

Contribution

It provides a detailed analysis of composite hole excitations in the t-J model, highlighting their momentum-dependent localization and influence on spectral properties in 1D and 2D.

Findings

Composite excitations with string-like spins are localized at k=π/2 in 1D.

Composite excitations with non-local spin fluctuations have stronger spectral intensity near the Fermi level in 2D.

The band structure along (0,0)-(π,π) in 2D resembles 1D, impacting pseudogap formation.

Abstract

We examine spectral properties of doped holes dressed with surrounding spin cloud in the t-J model. These composite-hole excitations well characterize prominent band structures in the angle-resolved photoemission spectrum. In one-dimensional (1D) case at half-filling, we identify the composite operators that separately pick up the spinon and holon branches, respectively. After hole doping, we find that the composite hole excitations with string-like spins tend to be localized at k=\pi/2 in the momentum space. This means that such composite excitations should be actual electronic excitations, since the spinon and holon branches merge together at this momentum. In 2D case, we find that the composite excitations with more non-local spin fluctuation have stronger intensity near the Fermi level. The composite band structure along diagonal (0,0)-(\pi,\pi) direction in 2D has some similarity to that in 1D, and such non-local spin fluctuation plays an important role on the formation of the pseudogap in high-Tc cuprates.