Unraveling local spin polarization of Zhang-Rice singlet in lightly hole-doped cuprates using high-energy optical conductivity

Abstract

Unrevealing local magnetic and electronic correlations in the vicinity of charge carriers is crucial in order to understand rich physical properties in correlated electron systems. Here, using high-energy optical conductivity (up to 35 eV) as a function of temperature and polarization, we observe a surprisingly strong spin polarization of the local spin singlet with enhanced ferromagnetic correlations between Cu spins near the doped holes in lightly hole-doped La 1.95 Sr 0.05 Cu 0.95 Zn 0.05 O 4 . The changes of the local spin polarization manifest strongly in the temperature-dependent optical conductivity at ~7.2 eV, with an anomaly at the magnetic stripe phase (~25K), accompanied by anomalous spectral-weight transfer in a broad energy range. Supported by theoretical calculations, we also assign high-energy optical transitions and their corresponding temperature dependence, particularly at ~2.5eV, ~8.7eV, ~9.7eV, ~11.3eV and ~21.8 eV. Our result shows the importance of a strong mixture of spin singlet and triplet states in hole-doped cuprates and demonstrates a new strategy to probe local magnetic correlations using highenergy optical conductivity in correlated electron systems.

Relevance of Cu–3d multiplet structure in models of high- Tc cuprates

“…Projecting onto these ZRS then allows one to map the three-band Emery model onto a single-band t-J model, 4 although a more careful treatment reveals the existence of additional terms ignored by the t-J Hamiltonian. 5,6 Although various analytical approximations and extensive numerical studies of these model Hamiltonians have revealed many insights in the past decades, the validity of the ZRS concept 7,8 and more generally the equivalence -or lack thereof -between the low-energy properties of one-and three-orbital models are still under debate. On one hand, the existence and stability of states with ZRS-like character have been confirmed in previous photoemission experiments.…”

Tunable Spin Correlated‐Plasmons Ranging from Infrared to Ultraviolet in Pr0.6Sr0.4Co1−xMnxO3

“…[ 8,9 ] Recently, electronic correlation has been found to be responsible for a strong mixture of spin‐singlet and triplet states yielding a strong spin polarization of the local spin‐singlet with enhanced ferromagnetic correlations in hole‐doped cuprates. [ 10 ] Despite these possibilities, stable spin plasmons have not been observed in crystalline 3D solids due to mainly the reason associated with the relaxation process of the spin plasmonic excitations. Unlike the charge plasmon, in which the momentum conservation makes this vibration stable, the collective oscillation of the spins decays very fast according to the random phase approximation (RPA) theory.…”

Observation of strong helical excitons and unexpectedly giant Rashba splitting in single crystal two-dimensional Organic-Inorganic Halide Perovskites

“…In this Letter, we use high-resolution and angle-dependent spectroscopic ellipsometry (SE) to directly probe electronic and optical fine structure of ((CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1 to 4) and establish a relationship between the Rashba effect and the thickness of the QW through RPPs. Spectroscopic ellipsometry is the most direct and self-normalized technique to simultaneously probe excitons and spin excitation, which have been shown successfully in transition metal oxides 24 . We perform polarization-dependent X-ray absorption spectroscopy (XAS) measurements at the C K-edge to reveal the surface symmetry broken.…”

“…The optical fine structure is the most direct and important property in revealing helical excitons 24 as well as Rashba splitting (c.f. Figs.…”

“…This is the first observation of the theoretically predicted multiple helical excitons in 2D RPPs. Because SE is very sensitive to spin excitations 24 ; the energy ordering and huge intensity of ε1 and ε2 below the interband transitions also rule out the origins of these peaks as defect or conventional excitons.…”