Angle-Resolved Photoemission Spectroscopy of Tetragonal CuO: Evidence for Intralayer Coupling Between Cupratelike Sublattices

Abstract

We investigate by angle-resolved photoemission the electronic structure of in situ grown tetragonal CuO, a synthetic quasi-two-dimensional edge-sharing cuprate. We show that, in spite of the very different nature of the copper oxide layers, with twice as many Cu in the CuO layers of tetragonal CuO as compared to the CuO 2 layers of the high-T c cuprates, the low-energy electronic excitations are surprisingly similar, with a Zhang-Rice singlet dispersing on weakly coupled cupratelike sublattices. This system should thus be considered as a member of the high-T c cuprate family, with, however, interesting differences due to the intralayer coupling between the cupratelike sublattices.

Non-Zhang-Rice Singlet Character of the First Ionization State of T-CuO

“…2 appears in the ARPES of "magnetically untwinned" T-CuO films in the insulating limit. This is very different and thus easily distinguishable from the one-band model prediction [22]. The observation of this pattern, with shallower displaced minima in two quadrants, will provide a clear proof of low-energy physics beyond the ZRS, and of the superiority of three-band models to model such materials.…”

“…ARPES finds the T-CuO qp dispersion to obey C 4 symmetry and to have a large BZ, corresponding to a unit cell containing one Cu and one O atom [22]. Both features are very surprising for the long-range magnetic orders of Figs.…”

“…The resulting qp dispersion was measured by angle resolved photoemission spectroscopy (ARPES) [22]. It seems to be quite similar to that of CuO 2 and was argued to be well described by the t-t ′ -t ′′ -J model [22].…”

Magnons in tetragonal CuO

“…This lifts the magnon degeneracy along X and produces two magnon branches which are simultaneously measured by RIXS. To see the trend of nonzero intersublattice coupling t d , we first keep U , t, t , and t at the SCOC values and include an additional t d = 100 meV estimated by ARPES [10,11]. The result is the black solid curve in Fig.…”

“…As ARPES finds a significant coupling between sublattices [11], we further study the effect of t d ∼ 100 meV on the magnon dispersion. Even if the magnetic properties are still expected to be dominated by J , t d will introduce a small but finite exchange term J d between sublattices.…”