Josephson plasma resonance and phonon anomalies in trilayer Bi_2Sr_2Ca_2Cu_3O_10 superconductor

TL;DR

This study investigates the c axis infrared conductivity of a trilayer Bi2223 superconductor, revealing a Josephson plasmon, phonon anomalies, and their implications for superconducting energy and electric field variations.

Contribution

It provides new insights into Josephson plasma resonance and phonon anomalies in trilayer cuprate superconductors using ellipsometry measurements.

Findings

Identification of a Josephson plasmon near 500 cm$^{-1}$

Observation of phonon anomalies linked to Josephson currents

Significant violation of the Ferrell-Glover-Tinkham sum-rule

Abstract

The far-infrared (FIR) c axis conductivity of a Bi2223 crystal has been measured by ellipsometry. Below T$_c$ a strong absorption band develops near 500 cm $^{-1}$, corresponding to a transverse Josephson-plasmon. The related increase in FIR spectral weight leads to a giant violation of the Ferrell-Glover-Tinkham sum-rule. The gain in c axis kinetic energy accounts for a sizeable part of the condensation energy. We also observe phonon anomalies which suggest that the Josephson-currents lead to a drastic variation of the local electric field within the block of closely spaced CuO$_2$ planes.