Yin Xinmao, Tang Chi Sin, Majidi Muhammad Aziz, Ren Peng, Wang Le, Yang Ping, Diao Caozheng, Yu Xiaojiang, Breese Mark B H, Wee Andrew T S, Wang Junling, Rusydi Andrivo
Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore.
SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering , Shenzhen University , Shenzhen 518060 , China.
ACS Appl Mater Interfaces. 2018 Oct 17;10(41):35563-35570. doi: 10.1021/acsami.7b15347. Epub 2018 Oct 8.
Hole-doped perovskite manganites have attracted much attention because of their unique optical, electronic, and magnetic properties induced by the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, a comprehensive investigation of the optical, electronic, and magnetic properties of LaSrMnO thin films on SrTiO (LSMO/STO) and other substrates is conducted using a combination of temperature-dependent transport, spectroscopic ellipsometry, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. A significant difference in the optical property of LSMO/STO that occurs even in thick (87.2 nm) LSMO/STO from that of LSMO on other substrates is discovered. Several excitonic features are observed in thin film nanostructure LSMO/STO at ∼4 eV, which could be attributed to the formation of anomalous charged excitonic complexes. On the basis of the spectral weight transfer analysis, anomalous excitonic effects from STO strengthen the electronic correlation in LSMO films. This results in the occurrence of optical spectral changes related to the intrinsic Mott-Hubbard properties in manganites. We find that while lattice strain from the substrate influences the optical properties of the LSMO thin films, the coexistence of strong electron-electron (e-e) and electron-hole (e-h) interactions which leads to the resonant excitonic effects from the substrate plays a much more significant role. Our result shows that the onset of anomalous excitonic dynamics in manganite oxides may potentially generate new approaches in manipulating exciton-based optoelectronic applications.
空穴掺杂的钙钛矿锰氧化物因其自旋、电荷、轨道和晶格自由度之间的相互作用所诱导的独特光学、电学和磁学性质而备受关注。在此，我们结合变温输运、椭圆偏振光谱、X射线吸收光谱和X射线磁圆二色性，对生长在SrTiO（LSMO/STO）及其他衬底上的LaSrMnO薄膜的光学、电学和磁学性质进行了全面研究。我们发现，即使是厚达87.2 nm的LSMO/STO薄膜，其光学性质与生长在其他衬底上的LSMO薄膜也存在显著差异。在薄膜纳米结构LSMO/STO中，在约4 eV处观察到了几个激子特征，这可能归因于反常带电激子复合物的形成。基于光谱权重转移分析，来自STO的反常激子效应增强了LSMO薄膜中的电子关联。这导致了与锰氧化物中本征莫特-哈伯德性质相关的光谱变化。我们发现，虽然衬底的晶格应变会影响LSMO薄膜的光学性质，但强电子-电子（e-e）和电子-空穴（e-h）相互作用的共存导致了来自衬底的共振激子效应，这一作用更为显著。我们的结果表明，锰氧化物中反常激子动力学的出现可能会为基于激子的光电子应用带来新的操控方法。
