Zooming on the Quantum Critical Point in Nd-LSCO

TL;DR

This study investigates the quantum critical point in Nd-LSCO by analyzing c-axis resistivity, revealing the precise doping level where stripe order ends and linking it to the pseudogap phase onset.

Contribution

It provides the first detailed measurement of c-axis resistivity near the QCP in Nd-LSCO, pinpointing the stripe order termination point with high precision.

Findings

Stripe order ends at doping p* = 0.235 ± 0.005.

The pseudogap phase onset temperature T_rho is roughly twice the stripe ordering temperature.

c-axis resistivity shows an upturn at low temperature indicating Fermi surface reconstruction.

Abstract

Recent studies of the high-Tc superconductor La_(1.6-x)Nd_(0.4)Sr_(x)CuO_(4) (Nd-LSCO) have found a linear-T in-plane resistivity rho_(ab) and a logarithmic temperature dependence of the thermopower S / T at a hole doping p = 0.24, and a Fermi-surface reconstruction just below p = 0.24 [1, 2]. These are typical signatures of a quantum critical point (QCP). Here we report data on the c-axis resistivity rho_(c)(T) of Nd-LSCO measured as a function of temperature near this QCP, in a magnetic field large enough to entirely suppress superconductivity. Like rho_(ab), rho_(c) shows an upturn at low temperature, a signature of Fermi surface reconstruction caused by stripe order. Tracking the height of the upturn as it decreases with doping enables us to pin down the precise location of the QCP where stripe order ends, at p* = 0.235 +- 0.005. We propose that the temperature T_(rho) below which the upturn begins marks the onset of the pseudogap phase, found to be roughly twice as high as the stripe ordering temperature in this material.