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Published August 15, 2016 | Published + Submitted
Journal Article Open

Signatures of strong correlation effects in resonant inelastic x-ray scattering studies on cuprates

Abstract

Recently, spin excitations in doped cuprates have been measured using resonant inelastic x-ray scattering. The paramagnon dispersions show the large hardening effect in the electron-doped systems and seemingly doping independence in the hole-doped systems, with the energy scales comparable to that of the antiferromagnetic (AFM) magnons. This anomalous hardening effect and the lack of softening were partially explained by using the strong-coupling t−J model but with a three-site term [Nat. Commun. 5, 3314 (2014)], although the hardening effect is already present even without the latter. By considering the t−t′−t"−J model and using the slave-boson mean-field theory, we obtain, via the spin-spin susceptibility, the spin excitations in qualitative agreement with the experiments. The doping-dependent bandwidth due to the strong correlation physics is the origin of the hardening effect. We also show that dispersions in the AFM regime, different from those in the paramagnetic (PM) regime, hardly vary with dopant density. These excitations are mainly collective in nature instead of particle-hole-like. We further discuss the interplay and different contributions of these two kinds of excitations in the PM phase and show that the dominance of the collective excitation increases with decreasing dopant concentrations.

Additional Information

© 2016 American Physical Society. Received 18 April 2016; revised manuscript received 21 July 2016; published 12 August 2016. The authors acknowledge useful discussions with Dr. Sung-Po Chao (Academia Sinica, Taiwan). In particular, we would like to thank Dr. Wei-Sheng Lee (Stanford Linear Accelerator Center, a National Accelerator Laboratory) for sharing with us some of the experimental data before it was published and also for many stimulating discussions. W.-J.L., C.-J.L., and T.-K.L. acknowledge support by Ministry of Science and Technology (MOST) in Taiwan (Grant No. 104-2112-M-001-005).

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Published - PhysRevB.94.075127.pdf

Submitted - 1604.01858v3.pdf

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