Development of spin-wave-like dispersive excitations below the pseudogap temperature in the high-temperature superconductor LaSrCuO

高温超伝導体LaSrCuOにおける擬ギャップ温度以下でのスピン波的励起の発達

松浦 直人*; 川村 奨*; 藤田 全基*; 梶本 亮一  ; 山田 和芳*

Matsuura, Masato*; Kawamura, Sho*; Fujita, Masaki*; Kajimoto, Ryoichi; Yamada, Kazuyoshi*

Inelastic neutron scattering measurements of magnetic excitations in hole-doped high- cuprates LaSrCuO ( and 0.075) have been performed over a wide temperature range of 5 500 K extending beyond the pseudogap temperature of 360 K for . For , the two-dimensional spin-wave excitations at low temperatures are thermally robust and the dispersion is slightly softened on heating up to K. For , the spin-wave-like excitations in the upper part of the hourglass-shaped dispersion remain at K. However, further heating above K induces a broad ridge centered at ; thereby the hourglass-shaped dispersion becomes blurred above the pseudogap temperature. The localized spin nature of magnetic excitations below suggests that the pseudogap is related to a proximity to a Mott insulator rather than being a precursor of Cooper pairs.