Possible superconductivity from incoherent carriers in overdoped cuprates

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 ns(0) of overdoped cuprates exhibits an anomalous depletion with increased hole doping p, falling to zero at the edge of the superconducting dome. Over the same doping range, the effective zero-temperature Hall number nH(0) transitions from p to 1 + p. By taking into account the presence of these two charge sectors, we demonstrate that in the overdoped cuprates Tl2Ba2CuO6+δ and La2−xSrxCuO4, the growth in ns(0) as p 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.