Interpreting Angle Dependent Magnetoresistance in Layered Materials: Application to Cuprates

TL;DR

This paper develops a theoretical framework for interpreting angle-dependent magnetoresistance (ADMR) in layered cuprate materials, emphasizing the role of quasiparticle weights and Fermi surface reconfigurations, to better understand doping-dependent electronic structures.

Contribution

It introduces a model incorporating angle-dependent quasiparticle weights and Fermi surface changes to explain ADMR data in cuprates, challenging previous interpretations involving spin density waves.

Findings

Proper inclusion of quasiparticle weights refutes the spin density wave interpretation.

A Fermi surface reconfiguration model explains doping-dependent ADMR differences.

Despite large Fermi surface at p=0.21, the model aligns with small Fermi surface evidence.

Abstract

The evolution of the low temperature electronic structure of the cuprate metals from the overdoped to the underdoped side has recently been addressed through Angle-Dependant Magneto-Resistance (ADMR) experiments in La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$. The results show a striking difference between hole dopings $p = 0.24$ and $p = 0.21$ which lie on either side of a putative quantum critical point at intermediate $p$. Motivated by this, we here study the theory of ADMR in correlated layered materials, paying special attention to the role of angle dependent quasiparticle weights $Z_{\mathbf{k}}$. Such a $Z_{\mathbf{k}}$ is expected to characterize a number of popular models of the cuprate materials, particularly when underdoped. Further, in the limit of weak interlayer hopping the quasiparticle weight will affect the $c$-axis transport measured in ADMR experiments. We show that proper inclusion of the quasiparticle weight does not support an interpretation of the data in terms of a $(\pi, \pi)$ spin density wave ordered state, in agreement with the lack of direct evidence for such order. We show that a simple model of Fermi surface reconfiguring across a van Hove point captures many of the striking differences seen between $p = 0.21$ and $p = 0.24$. We comment on why such a model may be appropriate for interpreting the ADMR data, despite having a large Fermi surface at $p = 0.21$, seemingly in contradiction with other evidence for a small Fermi surafce at that doping level.