Quasiparticle Spectra, Charge-Density Waves, Superconductivity, and Electron-Phonon Coupling in 2H–NbSe₂

T. Valla, A. V. Fedorov, and P. D. Johnson

Department of Physics, Brookhaven National Laboratory, Upton, New York, 11973-5000, USA

P-A. Glans, C. McGuinness, and K. E. Smith

Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA

E. Y. Andrei

Department of Physics, Rutgers University, 126 Frelinghuysen Road, Piscataway, New Jersey 08854, USA

H. Berger

Institute of Physics of Complex Matter, EPFL, Lausanne, Switzerland

(Received 18 August 2003; published 24 February 2004)

High-resolution photoemission has been used to study the electronic structure of the charge-density wave (CDW) and superconducting dichalcogenide, 2H–NbSe₂. From the extracted self-energies, important components of the quasiparticle interactions have been identified. In contrast to previously studied TaSe₂, the CDW transition does not affect the electronic properties significantly. The electron-phonon coupling is identified as a dominant contribution to the quasiparticle self-energy and is shown to be very anisotropic (k dependent) and much stronger than in TaSe₂. ©2004 The American Physical Society