Probing quasiparticle excitations in a doped Mott insulator via Friedel oscillations

TL;DR

This paper studies impurity effects in a doped Mott insulator, revealing how quasiparticle excitations influence Friedel oscillations and lead to phase separation, providing new insights into charge carriers in strongly correlated systems.

Contribution

It demonstrates that impurity-induced Friedel oscillations reflect non-fermionic quasiparticles and explores the transition to phase separation in the doped Hubbard model.

Findings

Friedel oscillations are consistent with non-interacting quasiparticles.

Wavevector violations of Luttinger's theorem are observed.

System undergoes phase separation at higher impurity strengths.

Abstract

In this work, we investigate impurity-induced Friedel oscillations in the doped two-dimensional Hubbard model, focusing on the role of holon and doublon excitations. We show that weak impurities, due to the non-fermionic nature of the underlying quasiparticles, induce Friedel oscillations whose behavior is consistent with an effective non-interacting theory for these quasiparticles, and whose wavevector reflects the violation of Luttinger's theorem. At larger impurity strength, the system transitions to a phase-separated state composed of coexisting Mott-insulating (half-filled) and hole-rich regions. Within the composite operator framework, this phase separation arises from a competition between the kinetic energy of holons and the tendency to form tightly bound holon-doublon pairs. Our results offer new insights into the nature of charge carriers and the emergent electronic phases in the doped Mott regime.