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- Title
Quantum critical behaviour in a high-T<sub>c</sub> superconductor.
- Authors
van der Marel, D.; Molegraaf, H.J.A.; Zaanen, J.; Nussinov, Z.; Carbone, F.; Damascelli, A.; Eisaki, H.; Greven, M.; Kes, P.H.; Li, M.
- Abstract
Quantum criticality is associated with a system composed of a nearly infinite number of interacting quantum degrees of freedom at zero temperature, and it implies that the system looks on average the same regardless of the time- and length scale on which it is observed. Electrons on the atomic scale do not exhibit such symmetry, which can only be generated as a collective phenomenon through the interactions between a large number of electrons. In materials with strong electron correlations a quantum phase transition at zero temperature can occur, and a quantum critical state has been predicted, which manifests itself through universal power-law behaviours of the response functions. Candidates have been found both in heavy-fermion systems and in the high-transition temperature (high-Tc) copper oxide superconductors, but the reality and the physical nature of such a phase transition are still debated. Here we report a universal behaviour that is characteristic of the quantum critical region. We demonstrate that the experimentally measured phase angle agrees precisely with the exponent of the optical conductivity. This points towards a quantum phase transition of an unconventional kind in the high-Tc superconductors.
- Subjects
QUANTUM biochemistry; COPPER oxide; SUPERCONDUCTORS; COUPLING constants; HIGH temperatures
- Publication
Nature, 2003, Vol 425, Issue 6955, p271
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature01978