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Published online: 16 April 2008 | doi:10.1038/nchina.2008.82

High-temperature superconductivity: Mysterious couplings

Felix Cheung

Introduction

© (2008) APS

High-temperature superconductors, which lose all electrical resistance at temperatures above the boiling point of liquid nitrogen (77 K), could herald a technological age of extremely compact, energy-efficient devices and super magnets. Xingjiang Zhou at the Chinese Academy of Sciences in Beijing and co-workers¹ have discovered a form of electron coupling in an optimally doped Bi₂Sr₂CaCu₂O₈ (Bi2212) superconductor that might explain the origin of high-temperature superconductivity.

Low-temperature superconductors have been known to lose their electrical resistance through the formation of electron pairs; two electrons, which would naturally repel each other, can pair up when one of them couples with a phonon (a lattice vibration).

Electron couplings in high-temperature superconductors, however, are a little more complex. For example, electrons with an energy around 70 meV have been known to couple with bosons (low-energy collective excitations).

Zhou and co-workers used a powerful tool, known as angle-resolved photoemission spectroscopy (ARPES), to probe the electron dynamics in the Bi2212 superconductor. The energy spectra (pictured, scale value not shown) featured a prominent kink at 70 meV. Through numerical analysis, the researchers further revealed two fine features in the energy spectra at 115 meV and 150 meV.

The additional fine features, which cannot be explained by electron–phonon coupling, hint at a new form of electron coupling in high-temperature superconductors. The nature of this electron coupling is yet to be determined, but the finding provides scientists with an invaluable piece of information in the puzzling physics of high-temperature superconductivity.

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; Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, USA; Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Japan; Laboratory for Optics, 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. Zhang, W. et al. Identification of a new form of electron coupling in the Bi₂Sr₂CaCu₂O₈ superconductor by laser-based angle-resolved photoemission spectroscopy. Phys. Rev. Lett. 100, 107002 (2008). | Article | PubMed | ChemPort |