Emergence of coherence in the charge-density wave state of 2H-NbSe2

U Chatterjee; J Zhao; M Iavarone; R Di Capua; J P Castellan; G Karapetrov; C D Malliakas; M G Kanatzidis; H Claus; J P C Ruff; F Weber; J van Wezel; J C Campuzano; R Osborn; M Randeria; N Trivedi; M R Norman; S Rosenkranz

doi:10.1038/ncomms7313

Emergence of coherence in the charge-density wave state of 2H-NbSe2

Nat Commun. 2015 Feb 17:6:6313. doi: 10.1038/ncomms7313.

Authors

U Chatterjee¹, J Zhao², M Iavarone³, R Di Capua³, J P Castellan⁴, G Karapetrov⁵, C D Malliakas⁶, M G Kanatzidis⁶, H Claus⁷, J P C Ruff⁸, F Weber⁴, J van Wezel⁹, J C Campuzano¹⁰, R Osborn⁷, M Randeria¹¹, N Trivedi¹¹, M R Norman⁷, S Rosenkranz⁷

Affiliations

¹ 1] Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA.
² 1] Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA [2] Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
³ Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA.
⁴ 1] Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] Institute of Solid State Physics, Karlsruhe Institute of Technology, PO Box 3640, D-76021 Karlsruhe, Germany.
⁵ Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, USA.
⁶ 1] Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
⁷ Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
⁸ 1] Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] CHESS, Cornell University, Ithaca, New York 14853, USA.
⁹ 1] Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] Institute for Theoretical Physics, University of Amsterdam, Tyndall Avenue, 1090 GL Amsterdam, The Netherlands.
¹⁰ 1] Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA [2] Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
¹¹ Department of Physics, Ohio State University, Columbus, Ohio 43210, USA.

Abstract

A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature T(cdw). Here we investigate, using photoemission, X-ray scattering and scanning tunnelling microscopy, the canonical CDW compound 2H-NbSe2 intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude, which has impacts on the electronic dispersion, giving rise to an energy gap. The phase transition at T(cdw) marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. Our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in 'pseudogap' states.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.