Isotope effects in underdoped cuprate superconductors: a quantum critical phenomenon.
We show that the unusual doping dependence of the isotope effects on transition temperature and zero temperature in-plane penetration depth naturally follows from the doping driven 3D-2D crossover and the 2D quantum superconductor to insulator transition in the underdoped limit. Since lattice distortions are the primary consequence of isotope substitution, our analysis clearly reveals the strong involvement of lattice degrees of freedom in mediating superconductivity.
Schneider
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Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Keller
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