過渡金屬氧化物La5/3Sr1/3NiO4調制結構的X-ray散射研究

Study of the charge stripes in transition metal oxide La5/3Sr1/3NiO4 using X-ray scattering

姚昌宏(Chang-Hung Yao)

指導教授 ： 杜昭宏

淡江大學/理學院/物理學系碩士班/碩士(2008年)

https://doi.org/10.6846/TKU.2008.00399

摘要

自從高溫超導La2-xSrxCuO4 (LSC)和La2-xBaxCuO4 (LBC)被發現後，高溫超導的機制一直是科學家廣為研究的課題。La2NiO4(LSN)與高溫的銅氧化物 La2-xSrxCuO4(LSC)及 La2-xBaxCuO4(LBC)為異質同構物。在LSC中藉由電洞載子的摻雜為超導材料並且超導相變溫度在Tsc= 35 K，但在異質同構物中，發現LSN摻雜高達至百分之七十的Sr時還是莫特絕緣體。此為材料中電子與聲子提供了強作用力影響所至。對於莫特絕緣體中的絕緣特性而言，這些行為產生的原因，確實是由於電子與聲子的交互作用所致。

從La2NiO4摻雜電洞的典型系統中，了解到化合物LSC、LBC相變的過程。我們利用高解析度的X光散射研究在低溫底下摻雜電洞的La2NiO4中電荷密度波所導致的調制結構，證明調制結構形成過程中擁有二維的系統和準長程有序的系統特性以及可能形成在相變溫度附近的電荷凝態狀態。

關鍵字

X光散射 ； 調制結構 ； 電荷條紋

並列摘要

Strontium-doped La2NiO4 (LSN) is isostructural with the high-TC cuprates, La2-xSrxCuO4 (LSC) and La2-xBaxCuO4 (LBC). With substitution of 15% Sr, LSC shows a superconducting transition at TSC=35 K, but LSN remains insulating at doping levels up to 70%. It has been suggested that stronger electron-phonon interactions in LSN are responsible for this behavior as it was recognized that electron-phonon interactions are critical for the persistent insulating character of the Mott insulator. Therefore the hole-doped La2NiO4 can serve on a prototypical system for the understanding of transport phenomena observed in compounds of LSC or LBC. Using high-resolution x-ray scattering, we investigated the modulations due to the hole-doped in La2NiO4, and demonstrated that the modulation possesses the characteristic of two-dimension in nature and quasi-long range order at low temperature and suggested the possible existence of charge liquid state around the transition temperature.

並列關鍵字

X-ray scattering ； charge stripes ； modulation

參考文獻

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