Friedel oscillations in a two-band Hubbard model for CuO chains

TL;DR

This study numerically investigates Friedel oscillations in a two-band Hubbard model for CuO chains, revealing 2k_F and 4k_F modulations depending on doping levels, aligning with experimental observations and highlighting the importance of distinct Luttinger liquid exponents.

Contribution

It provides the first detailed numerical analysis of Friedel oscillations in a realistic two-band Hubbard model for CuO chains, connecting theoretical predictions with experimental data.

Findings

Friedel oscillations show 2k_F modulation near quarter filling.

As doping decreases, oscillations shift to 4k_F modulation.

Results suggest different Luttinger liquid exponents for Cu and O subsystems.

Abstract

Friedel oscillations induced by open boundary conditions in a two-band Hubbard model for CuO chains are numerically studied. We find that for physically realistic parameters and close to quarter filling, these oscillations have a 2k_F modulation according with experimental results on YBa_2Cu_3O_{7-delta}. In addition, we predict that, for the same parameters, as hole doping is reduced from quarter filling to half filling, Friedel oscillations would acquire a 4k_F modulation, typical of a strongly correlated electrons regime. The 4k_F modulation dominates also in the electron doped region. The range of parameters varied is very broad, and hence the results reported could apply to other cuprates and other strongly correlated compounds with quasi-one dimensional structures. On a more theoretical side, we stress the fact that the copper and oxygen subsystems should be described by two different Luttinger liquid exponents.