Abstract
There is now compelling evidence that the normal state of superconducting overdoped cuprates is a strange metal comprising two distinct charge sectors, one governed by coherent quasiparticle excitations, the other seemingly incoherent and characterized by non-quasiparticle (Planckian) dissipation. The zero-temperature superfluid density n_s(0)ns(0) of overdoped cuprates exhibits an anomalous depletion with increased hole doping pp, falling to zero at the edge of the superconducting dome. Over the same doping range, the effective zero-temperature Hall number n_{\rm H}(0) transitions from pp to 1 + pp. By taking into account the presence of these two charge sectors, we demonstrate that in the overdoped cuprates Tl_22Ba_22CuO_{6+\delta}6+δ and La_{2-x}2−xSr_xxCuO_44, the growth in n_s(0)ns(0) as pp is decreased from the overdoped side may be compensated by the loss of carriers in the coherent sector. Such a correspondence is contrary to expectations from conventional BCS theory and implies that superconductivity in overdoped cuprates emerges uniquely from the sector that exhibits incoherent transport in the normal state.
Highlights
Given the presence of these two sectors, it is pertinent to pose the question: which sector is responsible for superconductivity? Here we show, with a minimal set of assumptions, that with decreasing doping, the superfluid density at 0 K (ns(0)) in Tl2201 and La2−x Srx CuO4 (LSCO) grows at the expense of the coherent carrier density
Our analysis reveals that the existing experimental data can be reconciled with a scenario in which these coherent and incoherent carriers are located on distinct regions of the underlying Fermi surface
Based on the assumption that the conductivities of these two sectors add in parallel, we have shown that in Tl2Ba2CuO6+δ, the growth of the superfluid density ns(0) with decreasing doping p is quantitatively compensated with the decrease in the coherent carrier density ncoh and that their sum is approximately equal to the full Luttinger count 1 + p
Summary
As in many other unconventional superconductors, the transition temperature Tc of high-Tc cuprates traces out a dome in their phase diagram. This doping-independent value for m∗ matches that obtained from quantum oscillation (QO) experiments on single crystals with Tc = 10 K and 27 K [37] as well as the normal state electronic specific heat coefficient γN for 0 K ≤ Tc ≤ 80 K [28]. The black dashed line ns(0)/(1 + p), (0)/ N n
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