Evolution of the Fermi surface with carrier concentration in Bi_2Sr_2CaCu_2O_{8+\delta}

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate the Fermi surface in underdoped Bi_2Sr_2CaCu_2O_{8+eta}, revealing a large Fermi surface consistent with precursor pairing rather than magnetic origins.

Contribution

It provides direct experimental evidence that the pseudogap phase in underdoped cuprates is associated with a large Fermi surface, challenging the idea of Fermi surface pockets or magnetic origins.

Findings

Large Fermi surface centered at ( extpi, extpi) in underdoped samples

No evidence of Fermi surface pockets around ( extpi/2, extpi/2)

Pseudogap likely of precursor pairing origin

Abstract

We show, by use of angle-resolved photoemission spectroscopy, that underdoped Bi_2Sr_2CaCu_2O_{8+\delta} appears to have a large Fermi surface centered at (\pi,\pi), even for samples with a T_c as low as 15 K. No clear evidence of a Fermi surface pocket around (\pi/2,\pi/2) has been found. These conclusions are based on a determination of the minimum gap locus in the pseudogap regime T_c < T < T^*, which is found to coincide with the locus of gapless excitations in momentum space (Fermi surface) determined above T^*. These results suggest that the pseudogap is more likely of precursor pairing rather than magnetic origin.