Coupled magnon-phonon excitations inSr2CuCl2O2

Abstract

High-pressure optical experiments have been performed on midinfrared excitations unique to the layered cuprates, yet whose physical origin has been unresolved. Measurements of high-pressure midinfrared spectra of Sr 2 CuCl 2 o 2 unambiguously identify the ϳ2800-cm Ϫ1 absorption as an unusual quasibound two-magnon ϩ phonon excitation. We further show that the broad peak centered near ϳ4000 cm Ϫ1 is a four-magnon ϩ phonon excitation, with spectral weight ϳ10 2 times larger than predicted by theory. These excitations reveal unusual latent interactions coupling charge, spin, and lattice degrees of freedom in the CuO 2 planes. PRB 62 V. V. STRUZHKIN et al.

Magnon–phonon coupling and implications for charge-density wave states and superconductivity in cuprates

“…Cooper and coworkers [26] proposed the explanation of the anomalous bond length dependence which followed from their experimental findings on M 2 CuO 4 where M = Pr, Nd, Sm, Eu, Gd. They used well known [27] expression for superexchange [22]. These measurements confirmed previous assignment of higher-energy bands (at ~4000 cm -1 ) to four-magnon excitations (see Fig.…”

“…In one of our papers, we have measured two-magnon Raman scattering [21] in a single layer parent antiferromagnetic cuprate Eu 2 CuO 4 . In another experiment, we utilized another powerful tool for probing magnetic interactions -infrared absorption -to measure coupled phonon-multimagnon excitations in Sr 2 CuCl 2 O 2 material [22] (two-magnon and four-magnon excitations coupled to phonons were measured). To understand underlying physics, a brief summary of two-magnon Raman experiments and theoretical treatments is given below.…”

“…Room-temperature MIR absorption and two-magnon Raman scattering spectra in SCOC at several pressures. The spectra are vertically offset for clarity [22].…”

Raman spectroscopy of metals, high‐temperature superconductors and related materials under high pressure

“…Similar measurements of coupled phonon and two-magnon excitations by Raman scattering and infrared absorption in the cuprate material Sr 2 CuCl 2 O 2 have also been reported. 141 Cu 2C and Ni 2C ions have a quenched orbital momentum and small single-ion anisotropy; the only report on multiple Raman-active one-magnon excitations in these compounds has appeared for a folded spin-wave branch due to the static spin-density wave in La 2 CuO 4 142 at ambient pressure. It is desirable to extend the investigations to other antiferromagnetic compounds with unquenched orbital momentum in order to improve our understanding of the magnetic properties of these materials.…”

Silverland: the Realm of Compounds of Divalent Silver—and Why They are Interesting

“…in establishing the J values for oxocuprates in both 1D [76] and 2D [77,78] systems. In early 2017, I have contacted José Lorenzana, excellent theoretical physicist of Argentinian origin working in Italy, and with his guidance, our experimental data collected by my hardworking PhD student, Jakub Gawraczyński, for 1D AgFBF 4 and for 2D AgF 2 , could finally be rationalized and will be published soon.…”