The rate of quasiparticle recombination probes the onset of coherence in cuprate superconductors

In the underdoped copper-oxides, high-temperature superconductivity condenses from a nonconventional metallic "pseudogap" phase that exhibits a variety of non-Fermi liquid properties. Recently, it has become clear that a charge density wave (CDW) phase exists within the pseudogap regime. T...

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Bibliographic Details
Published in:	Scientific reports 2016-04, Vol.6 (1), p.23610-23610, Article 23610
Main Authors:	Hinton, J P, Thewalt, E, Alpichshev, Z, Mahmood, F, Koralek, J D, Chan, M K, Veit, M J, Dorow, C J, Barišić, N, Kemper, A F, Bonn, D A, Hardy, W N, Liang, Ruixing, Gedik, N, Greven, M, Lanzara, A, Orenstein, J
Format:	Article
Language:	eng
Subjects:	CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY Crystals Laboratories Magnetic fields MATERIALS SCIENCE Oxides Physics Probes Recombination superconducting properties and materials Temperature Temperature effects
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Summary:	In the underdoped copper-oxides, high-temperature superconductivity condenses from a nonconventional metallic "pseudogap" phase that exhibits a variety of non-Fermi liquid properties. Recently, it has become clear that a charge density wave (CDW) phase exists within the pseudogap regime. This CDW coexists and competes with superconductivity (SC) below the transition temperature Tc, suggesting that these two orders are intimately related. Here we show that the condensation of the superfluid from this unconventional precursor is reflected in deviations from the predictions of BSC theory regarding the recombination rate of quasiparticles. We report a detailed investigation of the quasiparticle (QP) recombination lifetime, τqp, as a function of temperature and magnetic field in underdoped HgBa2CuO(4+δ) (Hg-1201) and YBa2Cu3O(6+x) (YBCO) single crystals by ultrafast time-resolved reflectivity. We find that τqp(T) exhibits a local maximum in a small temperature window near Tc that is prominent in underdoped samples with coexisting charge order and vanishes with application of a small magnetic field. We explain this unusual, non-BCS behavior by positing that Tc marks a transition from phase-fluctuating SC/CDW composite order above to a SC/CDW condensate below. Our results suggest that the superfluid in underdoped cuprates is a condensate of coherently-mixed particle-particle and particle-hole pairs.
ISSN:	2045-2322 2045-2322