Acoustic plasmons and conducting carriers in hole-doped cuprate superconductors

Abstract

The superconductivity of cuprates, which has been a mystery ever since its discovery decades ago, is created through doping electrons or holes into a Mott insulator. There, however, exists an inherent electron-hole asymmetry in cuprates. The layered crystal structures of cuprates enable collective charge excitations fundamentally different from those of three-dimensional metals, i.e., acoustic plasmons. Acoustic plasmons have been recently observed in electron-doped cuprates by resonant inelastic X-ray scattering (RIXS); in contrast, there is no evidence for acoustic plasmons in hole-doped cuprates, despite extensive measurements. This contrast led us to investigate whether the doped holes in cuprates La${}_{2-x}$Sr${}_x$CuO${}_4$ are conducting carriers or are too incoherent to induce collective charge excitation. Here we present momentum-resolved RIXS measurements and calculations of collective charge response via the loss function to reconcile the aforementioned issues. Our results provide unprecedented spectroscopic evidence for the acoustic plasmons and long sought conducting p holes in hole-doped cuprates.

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• Gapped collective charge excitations and interlayer hopping in cuprate superconductors
• Evolution of plasmon excitations across the phase diagram of the cuprate superconductor La${}_{2-x}$Sr${}_x$CuO${}_4$
• A unified theory of spin and charge excitations in high-$T_c$ cuprates: Quantitative comparison with experiment and interpretation
• Plasmon dispersion in bilayer cuprate superconductors
• Impact of electron correlations on two-particle charge response in electron- and hole-doped cuprates
• Low temperature dynamic polaron liquid in a manganite exhibiting colossal magnetoresistance
• Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry
• Theory of charge dynamics in bilayer electron system with long-range Coulomb interaction
• Ring-like shaped charge modulations in the t-J model with long-range Coulomb interaction
• Unusual Low-Energy Collective Charge Excitations in High-$T_c$ Cuprate Superconductors
• Low-energy plasmon excitations in infinite-layer nickelates
• Out-of-phase Plasmon Excitations in the Trilayer Cuprate Bi${}_2$Sr${}_2$Ca${}_2$Cu${}_3$O${}_{10+\delta }$
• Ghost Josephson plasmon in bilayer superconductors
• Spin and bond-charge excitation spectra in correlated electron systems near antiferromagnetic phase
• Plasmarons in high-temperature cuprate superconductors
• Optical absorption in tilted geometries as an indirect measurement of longitudinal plasma waves in layered cuprates
• Collective spin and charge excitations in the $t$-$J$-$U$ model of high-$T_c$ cuprates
• Charge density response in layered metals: retardation effects, generalized plasma waves and their spectroscopic signatures
• Reply to arXiv:2103.10268 `Comment on "Crossover of Charge Fluctuations across the Strange Metal Phase Diagram'''
• Retaining Landau quasiparticles in the presence of realistic charge fluctuations in cuprates
• Dynamic charge order from strong correlations in the cuprates
• Optical and acoustic plasmons in the layered material Sr${}_2$RuO${}_4$
• Gor'kov-Hedin-Baym Equations for Quantum Many-Body Systems with Spin-Dependent Interactions
• Bimagnon dispersion of La2CuO4 probed by resonant inelastic X-ray scattering
• Electron-hole asymmetry of quantum collective excitations in high-$T_c$ copper oxides
• Strongly correlated model of acousticlike plasmons persisting across the phase diagram of cuprate superconductors
• Beyond on-site Hubbard interaction in charge dynamics of cuprate superconductors
• Theoretical perspectives on charge dynamics in high-temperature cuprate superconductors
• Observation of correlated plasmons in low-valence nickelates