Closing of the pseudogap in Sr-doped and Nd-codoped lanthanum cuprate (LSCO, Nd-LSCO)

TL;DR

This paper investigates how doping La-based cuprates with Sr and Nd affects the pseudogap and charge order, revealing a quantum critical point where the pseudogap closes and specific charge order relations emerge.

Contribution

It introduces a detailed analysis of charge ordering and pseudogap behavior in doped La-based cuprates, identifying a quantum critical point with specific charge order relations.

Findings

Charge order forms a 2D incommensurate pattern in CuO2 and LaO layers.

Pseudogap closes at a critical doping level x* where charge order relations satisfy q^{CuO_2} = 2q^{LaO}.

Doping induces lattice defects that influence charge distribution and electronic properties.

Abstract

Doping of La_2CuO_4 and La_{1.6}Nd_{0.4}CuO_4 with Sr gives rise to holes that locate pairwise at lattice-site O atoms. Such O atoms reside as lattice defects in the CuO_2 planes if the doping level x is below a watershed value, x < x^, but also the bracketing LaO layers if x > x^. The O atoms form a 2D charge order of incommensurability q^{CuO_2}(x) and q^{LaO}(x). At the doping x* (quantum critical point) that causes the closing of the pseudogap at T=0, q^{CuO_2}(x*) = 2q^{LaO}(x*) holds.