Article abstract

Nature Physics 3, 720 - 725 (2007)
Published online: 12 August 2007 | doi:10.1038/nphys699

Subject Categories: Condensed-matter physics | Materials physics

Charge-order-maximized momentum-dependent superconductivity

T. Kiss1,2, T. Yokoya1,3, A. Chainani4,5, S. Shin1,5, T. Hanaguri2, M. Nohara6 & H. Takagi2,6

Charge ordering and superconductivity are observed in the phase diagrams of a variety of materials such as NbSe3, layered transition-metal dichalcogenides and high-temperature copper oxide superconductors, low-dimensional organics, Ba1-xKxBiO3 and so forth. Although both conventional charge-density-wave (CDW) and superconducting transitions show an energy gap in the single-particle density of states at the Fermi level (EF), their physical properties are poles apart: insulating behaviour for the CDW and zero resistivity in superconductors. Consequently, these two ground states are believed to compete with each other. Here we provide evidence for maximized superconductivity at points in momentum (k) space that are directly connected by the CDW ordering vector. Temperature-dependent angle-resolved photoemission spectroscopy of 2H-NbSe2 across the CDW and superconducting transitions (TCDWapprox33 K and Tc=7.2 K, respectively) shows CDW-induced spectral-weight depletion at the same Fermi-surface-crossing k points, which evolve into the largest superconducting gaps. These k points also show the highest electron–phonon coupling and lowest Fermi velocities. Our results demonstrate that charge order can boost superconductivity in an electron–phonon coupled system, in direct contrast to the prevailing view that it only competes with superconductivity.

  1. Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan
  2. Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan
  3. The Graduate School of Natural Science and Technology, Okayama University, Okayama, Okayama 700-8530, Japan
  4. Institute for Plasma Research, Bhat, Gandhinagar-382 428, India
  5. The Institute of Physical and Chemical Research (RIKEN), Sayo-gun, Hyogo 679-5143, Japan
  6. Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan

Correspondence to: T. Kiss1,2 e-mail:

Correspondence to: S. Shin1,5 e-mail: