Overdamped antiferromagnetic strange metal state in Sr$_3$IrRuO$_7

• Main Authors: Schmehr, Julian L, Mion, Thomas R, Porter, Zach, Aling, Michael, Cao, Huibo, Upton, Mary H, Islam, Zahirul, He, Rui-Hua, Sensarma, Rajdeep, Trivedi, Nandini, Wilson, Stephen D
• Format: Journal Article
• Language: English
• Published: 14.03.2019
• Subjects: Physics - Materials Science; Physics - Strongly Correlated Electrons
• DOI: 10.48550/arxiv.1903.06115

Phys. Rev. Lett. 122, 157201 (2019) The unconventional electronic ground state of Sr$_3$IrRuO$_7$ is explored via resonant x-ray scattering techniques and angle-resolved photoemission measurements. As the Ru content approaches $x=0.5$ in Sr$_3$(Ir$_{1-x}$Ru$_x$)$_2$O$_7$, intermediate to the $J_{eff}=1/2$ Mott state in Sr$_3$Ir$_2$O$_7$ and the quantum critical metal in Sr$_3$Ru$_2$O$_7$, a thermodynamically distinct metallic state emerges. The electronic structure of this intermediate phase lacks coherent quasiparticles, and charge transport exhibits a linear temperature dependence over a wide range of temperatures. Spin dynamics associated with the long-range antiferromagnetism of this phase show nearly local, overdamped magnetic excitations and an anomalously large energy scale of 200 meV---an energy far in excess of exchange energies present within either the Sr$_3$Ir$_2$O$_7$ or Sr$_3$Ru$_2$O$_7$ solid-solution endpoints. Overdamped quasiparticle dynamics driven by strong spin-charge coupling are proposed to explain the incoherent spectral features of the strange metal state in Sr$_3$IrRuO$_7$.