Research Highlights

• Subject Categories:
  • Physics
  • Materials

Published online: 9 December 2009 | doi:10.1038/nchina.2009.235

Condensed matter physics: Arcs and pockets

Felix Cheung

Introduction

© (2009) Nature

The origin of superconductivity is arguably the biggest riddle in today's physics. Most scientists believe that the answer may lie in the paired electrons within the superconductor. Xingjiang Zhou and co-workers at the Chinese Academy of Sciences in Beijing¹ have used angle-resolved photoemission spectroscopy to study the Fermi surface — an abstract interface that defines the allowable energies of electrons in solids — of a copper-oxide superconductor. They found unexpected Fermi features that make this riddle even more perplexing.

The shape of the Fermi surface can provide much useful information about the dynamic behaviour of electrons, and thereby the electrical and magnetic properties of a solid. In ordinary metals, the Fermi surface is a closed loop, which indicates that the electrons behave similarly for any direction of motion.

Previous studies have seen open-ended gapless sections — called 'Fermi arcs' — in the Fermi surface of high-temperature copper-oxide superconductors. This time, the researchers observed small closed features — called 'Fermi pockets' (see image, Fermi pockets are marked LP) — in the copper-oxide superconductor Bi₂Sr_2-xLa_xCuO₆₊. The most surprising thing is that these Fermi pockets appear to coexist with Fermi arcs.

Recent quantum oscillation measurements have suggested the existence of these Fermi pockets. However, the theory did not predict the coexistence of both arcs and pockets. The researchers believe their new findings will provide key insights for understanding the role of paired electrons in high-temperature superconductors.

The authors of this work are from:
National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China; Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China.

Reference

1. Meng, J. et al. Coexistence of Fermi arcs and Fermi pockets in a high-T_c copper oxide superconductor. Nature 462, 335–338 (2009).  | Article | PubMed | OpenURL | | ChemPort |