The Origin and Non-quasiparticle Nature of Fermi Arcs in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$

TL;DR

This study reveals that Fermi arcs in cuprate superconductors are composed of non-quasiparticle spectral weight shifted by pair-breaking, challenging the notion that they form true Fermi surfaces and providing new insights into the pseudogap phase.

Contribution

We developed a novel photoemission technique to directly analyze the spectral weight and quasiparticle nature of Fermi arcs, demonstrating they lack true quasiparticles despite real spectral weight.

Findings

Fermi arcs lack quasiparticles to be true Fermi surfaces.

Spectral weight is shifted from the gap edge to the Fermi energy by pair-breaking.

Fermi arcs are composed of non-quasiparticle spectral weight.

Abstract

A Fermi arc is a disconnected segment of a Fermi surface observed in the pseudogap phase of cuprate superconductors. This simple description belies the fundamental inconsistency in the physics of Fermi arcs, specifically that such segments violate the topological integrity of the band. Efforts to resolve this contradiction of experiment and theory have focused on connecting the ends of the Fermi arc back on itself to form a pocket, with limited and controversial success. Here we show the Fermi arc, while composed of real spectral weight, lacks the quasiparticles to be a true Fermi surface. To reach this conclusion we developed a new photoemission-based technique that directly probes the interplay of pair-forming and pair-breaking processes with unprecedented precision. We find the spectral weight composing the Fermi arc is shifted from the gap edge to the Fermi energy by pair-breaking processes. While real, this weight does not form a true Fermi surface, because the quasiparticles, though significantly broadened, remain at the gap edge. This non-quasiparticle weight may account for much of the unexplained behavior of the pseudogap phase of the cuprates.