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arXiv 0904.0294cond-mat.str-elcond-mat.mtrl-sci
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二氧化钒绝缘体-金属转变的红外光谱和纳米成像

Infrared spectroscopy and nano-imaging of the insulator-to-metal transition in vanadium dioxide

M. M. Qazilbash, M. Brehm, G. O. Andreev, A. Frenzel, P. -C. Ho, Byung-Gyu Chae, Bong-Jun Kim, Sun Jin Yun, Hyun-Tak Kim, A. V. Balatsky, O. G. Shpyrko, M. B. M… 展开作者

M. M. Qazilbash, M. Brehm, G. O. Andreev, A. Frenzel, P. -C. Ho, Byung-Gyu Chae, Bong-Jun Kim, Sun Jin Yun, Hyun-Tak Kim, A. V. Balatsky, O. G. Shpyrko, M. B. Maple, F. Keilmann, D. N. Basov

摘要:

本文对二氧化钒(VO 2)薄膜的绝缘体-金属转变(IMT)进行了详细的红外研究。采用常规红外光谱法研究远场IMT。扫描近场红外显微镜直接揭示了随着温度的升高,减少IMT。我们证实了相变也与IMT的冷却有关。我们提出了广泛的近场红外图像相共存的IMT制度VO 2。我们发现,共存的绝缘和金属区域在一个固定的温度是静态的时间尺度上的测量。采用Bruggeman有效介质理论分析远场和近场红外数据的一种新方法,提取了IMT开始时初始金属熔池的光学常数。我们发现发散的有效载流子质量的金属水坑,证明了电子相关的IMT在VO 2的重要性。我们采用扩展的偶极子模型的定量分析所观察到的近场红外振幅对比度,并与基本偶极子模型所获得的结果进行比较。

英文摘要:

We present a detailed infrared study of the insulator-to-metal transition (IMT) in vanadium dioxide (VO2) thin films. Conventional infrared spectroscopy was employed to investigate the IMT in the far-field. Scanning near-field infrared microscopy directly revealed the percolative IMT with increasing temperature. We confirmed that the phase transition is also percolative with cooling across the IMT. We present extensive near-field infrared images of phase coexistence in the IMT regime in VO2. We find that the coexisting insulating and metallic regions at a fixed temperature are static on the time scale of our measurements. A novel approach for analyzing the far-field and near-field infrared data within the Bruggeman effective medium theory was employed to extract the optical constants of the incipient metallic puddles at the onset of the IMT. We found divergent effective carrier mass in the metallic puddles that demonstrates the importance of electronic correlations to the IMT in VO2. We employ the extended dipole model for a quantitative analysis of the observed near-field infrared amplitude contrast and compare the results with those obtained with the basic dipole model.

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