paper

Dispersive spin excitations in highly overdoped cuprates revealed by resonant inelastic x-ray scattering

arXiv:1303.3947 · doi:10.1103/PhysRevB.88.020501

Abstract

Using resonant inelastic x-ray scattering (RIXS) at the Cu $L$ -absorption edge, we have observed intense, dispersive spin excitations in highly overdoped Tl $_{2}$ Ba $_{2}$ CuO $_{6 + I^´}$ (superconducting $T_{c} = 6$ K), a compound whose normal-state charge transport and thermodynamic properties have been studied extensively and shown to exhibit canonical Fermi-liquid behavior. Complementary RIXS experiments on slightly overdoped Tl $_{2}$ Ba $_{2}$ CuO $_{6 + I^´}$ ( $T_{c} = 89$ K) and on Y $_{1 - x}$ Ca $_{x}$ Ba $_{2}$ Cu $_{3}$ O $_{6 + I^´}$ compounds spanning a wide range of doping levels indicate that these excitations exhibit energies and energy-integrated spectral weights closely similar to those of antiferromagnetic magnons in undoped cuprates. The surprising coexistence of Fermi-liquid-like charge excitations and high-energy spin excitations reminiscent of antiferromagnetic insulators in highly overdoped compounds poses a challenge to current theoretical models of the cuprates.