Nodal metallic behavior of lightly-doped La$_{2-x}$Sr$_x$CuO$_4$

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal nodal metallic behavior in lightly-doped La$_{2-x}$Sr$_x$CuO$_4$, showing a Fermi arc and spectral weight evolution consistent with increased hole doping.

Contribution

It provides direct spectroscopic evidence of nodal quasiparticles and Fermi arcs in the insulating spin-glass phase of lightly-doped cuprates, linking spectral features to doping levels.

Findings

Observation of a nodal quasiparticle peak crossing the Fermi level.

Fermi arc formation in the insulating spin-glass phase.

Spectral weight of the nodal QP increases with hole doping, matching carrier density behavior.

Abstract

Lightly-doped La$_{2-x}$Sr$_x$CuO$_4$ in the so-called "insulating" spin-glass/diagonal-stripe phase has been studied by angle-resolved photoemission spectroscopy. A quasi-particle (QP) peak crossing the Fermi level has been observed in the node direction of the d-wave superconducting gap, forming an "arc" of Fermi surface consistent with the recently observed metallic transport behavior at high temperatures of lightly-doped materials. The spectral weight of the nodal QP smoothly increases with hole doping, corresponding to the $n \sim x$ behavior of the carrier number in the underdoped and lightly-doped regions.