Josephson surface plasmons in spatially confined cuprate superconductors

TL;DR

This paper extends the theory of localized surface plasmons to high-temperature cuprate superconductors, revealing Josephson surface plasmons influenced by Josephson plasma waves, with implications for understanding and engineering superconducting properties.

Contribution

It introduces the concept of Josephson surface plasmons in spatially confined cuprate superconductors, linking surface excitations to Josephson plasma waves and anisotropic electromagnetic responses.

Findings

Identification of Josephson surface plasmons in confined cuprates

Detailed analysis for multilayered superconductors with JPWs

Potential to engineer plasmon frequencies via spatial confinement

Abstract

In this work, we generalize the theory of localized surface plasmons to the case of high-Tc cuprate superconductors, spatially confined in the form of small spherical particles. At variance from ordinary metals, cuprate superconductors are characterized by a low-energy bulk excitation known as the Josephson plasma wave (JPW), arising from interlayer tunneling of the condensate along the c-axis. The effect of the JPW is revealed in a characteristic spectrum of surface excitations, which we call Josephson surface plasmons. Our results, which apply to any material with a strongly anisotropic electromagnetic response, are worked out in detail for the case of multilayered superconductors supporting both low-frequency (acoustic) and transverse-optical JPW. Spatial confinement of the Josephson plasma waves may represent a new degree of freedom to engineer their frequencies and to explore the link between interlayer tunnelling and high-Tc superconductivity.