Three energy scales characterizing the competing pseudogap state, the incoherent, and the coherent superconducting state in high-Tc cuprates

TL;DR

This study identifies three distinct energy scales in high-Tc cuprates related to pseudogap, fluctuating, and coherent superconducting states, revealing their temperature dependencies and momentum-space behaviors.

Contribution

It provides direct experimental evidence for three separate energy scales and clarifies their relation to different temperature regimes in high-Tc cuprates.

Findings

Existence of three energy scales: Δ_pg, Δ_sc0, Δ_eff_sc0.

Pseudogap state exists below T* and competes with superconductivity.

Superconducting fluctuations occur around the antinode below Tonset.

Abstract

We have studied the momentum dependence of the energy gap of Bi2(Sr,R)2CuOy by angleresolved photoemission spectroscopy (ARPES), particularly focusing on the difference between R=La and Eu. By comparing the gap function and characteristic temperatures between the two sets of samples, we show that there exist three distinct energy scales, {\Delta}pg, {\Delta}sc0, and {\Delta}eff sc0, which correspond to T* (pseudogap temperature), Tonset (onset temperature of fluctuating superconductivity), and Tc (critical temperature of coherent superconductivity). The results not only support the existence of a pseudogap state below T* that competes with superconductivity but also the duality of competition and superconducting fluctuation at momenta around the antinode below Tonset.