Distinct Fermi-Momentum Dependent Energy Gaps in Deeply Underdoped Bi2212

TL;DR

This study uses angle-resolved photoemission spectroscopy to identify two distinct energy gaps in deeply underdoped Bi2212 cuprates, revealing different doping dependencies and suggesting a two-gap scenario relevant to high-Tc superconductivity.

Contribution

It provides the first direct evidence of two distinct Fermi-momentum dependent energy gaps in deeply underdoped cuprates, challenging single-gap models.

Findings

Antinodal gap increases with underdoping.

Nodal gap remains unchanged with underdoping.

Supports a two-gap scenario in high-Tc superconductors.

Abstract

We use angle-resolved photoemission spectroscopy applied to deeply underdoped cuprate superconductors Bi2Sr2(Ca,Y)Cu2O8 (Bi2212) to reveal the presence of two distinct energy gaps exhibiting different doping dependence. One gap, associated with the antinodal region where no coherent peak is observed, increases with underdoping - a behavior known for more than a decade and considered as the general gap behavior in the underdoped regime. The other gap, associated with the near nodal regime where a coherent peak in the spectrum can be observed, does not increase with less doping - a behavior not observed in the single particle spectra before. We propose a two-gap scenario in momentum space that is consistent with other experiments and may contain important information on the mechanism of high-Tc superconductivity.