Plasmarons in high-temperature cuprate superconductors

TL;DR

This paper investigates how plasmons influence electron dispersion in high-temperature cuprate superconductors, revealing the formation of plasmarons due to strong correlations, distinct from phonon or magnetic fluctuation effects.

Contribution

It demonstrates that optical plasmons create plasmarons in cuprates through bosonic fluctuations linked to electron correlations, a mechanism different from conventional charge-density fluctuations.

Findings

Plasmarons form in cuprates, affecting electron spectra.

Optical plasmons, not acoustic, are responsible for plasmarons.

Plasmarons are present in electron- and hole-doped cuprates, near superconducting and pseudogap regions.

Abstract

Metallic systems exhibit plasmons as elementary charge excitations. This fundamental concept was reinforced also in high-temperature cuprate superconductors recently, although cuprates are not only layered systems but also strongly correlated electron systems. Here, we study how such ubiquitous plasmons leave their marks on the electron dispersion in cuprates. In contrast to phonons and magnetic fluctuations, plasmons do not yield a kink in the electron dispersion. Instead, we find that the optical plasmon accounts for an emergent band -- plasmarons -- in the one-particle excitation spectrum; acoustic-like plasmons typical to a layered system are far less effective. Because of strong electron correlations, the plasmarons are generated by bosonic fluctuations associated with the local constraint, not by the usual charge-density fluctuations. Apart from this physical mechanism, the plasmarons are similar to those discussed in alkali metals, Bi, graphene, monolayer transition-metal dichalcogenides, semiconductors, diamond, two-dimensional electron systems, and SrIrO3 films, establishing a concept of plasmarons in metallic systems in general. Plasmarons are realized below (above) the quasiparticle band in electron-doped (hole-doped) cuprates, including a region around (pi,0) and (0,pi) where the superconducting gap and the pseudogap are most enhanced.