Reflective terahertz time-domain spectroscopy measurement on the stripe-ordered superconductor La$_{1.84-y}$Nd$_y$Sr$_{0.16}$CuO$_4$

TL;DR

This study used terahertz time-domain spectroscopy to measure reflectivity in stripe-ordered La-based cuprates, finding evidence against the existence of two-dimensional superconductivity in these materials.

Contribution

It provides the first reflectivity measurements on stripe-ordered La$_{1.84-y}$Nd$_y$Sr$_{0.16}$CuO$_4$ using THz-TDS, clarifying the presence of Josephson plasma edge and 2D superconductivity.

Findings

Josephson plasma edge observed, indicating inter-layer coupling.

Contradicts previous reports of 2D superconductivity in these compounds.

Provides new insights into the superconducting properties of stripe-ordered cuprates.

Abstract

We measured reflectivity on static stripe-ordered La$_{1.84-y}$Nd$_y$Sr$_{0.16}$CuO$_4$ (LNSCO) $y$\,=\,0.1, 0.2, 0.3, and 0.4 by means of reflective terahertz time-domain spectroscopy (THz-TDS) with electric field polarized along c-axis, in which one can obtain lower frequency information than the conventional Fourier transform type spectrometer. Recently, two-dimensional superconducting (2DSC) property \cite{tajima,schafgans,li}, intra-layer perfect conductivity not accompanied with inter-layer superconducting behavior, was reported on LNSCO ($x$\,=0.15\,,\,$y$\,$\geq$\,0.2). We observed the existence of Josephson plasma edge, which suggests that 2DSC is not realized in these compounds.