Slusar Tetiana V, Cho Jin-Cheol, Lee Hyang-Rok, Kim Ji-Wan, Yoo Seung Jo, Bigot Jean-Yves, Yee Ki-Ju, Kim Hyun-Tak
Metal-Insulator-Transition Laboratory, Electronics and Telecommunications Research Institute, Daejeon, 34129, Republic of Korea.
Department of Advanced Device Technology, University of Science and Technology, Daejeon, 34129, Republic of Korea.
Sci Rep. 2017 Nov 22;7(1):16038. doi: 10.1038/s41598-017-16188-6.
The characteristic of strongly correlated materials is the Mott transition between metal and insulator (MIT or IMT) in the same crystalline structure, indicating the presence of a gap formed by the Coulomb interaction between carriers. The physics of the transition needs to be revealed. Using VO, as a model material, we observe the emergence of a metallic chain in the intermediate insulating monoclinic structure (M2 phase) of epitaxial strained films, proving the Mott transition involving the breakdown of the critical Coulomb interaction. It is revealed by measuring the temperature dynamics of coherent optical phonons with separated vibrational modes originated from two substructures in M2: one is the charge-density-wave, formed by electron-phonon (e-ph) interaction, and the other is the equally spaced insulator-chain with electron-electron (e-e) correlations.
强关联材料的特性是在相同晶体结构中金属与绝缘体之间的莫特转变（金属-绝缘体转变或绝缘体-金属转变），这表明载流子之间的库仑相互作用形成了一个能隙。需要揭示这种转变的物理机制。以VO为例作为模型材料，我们在外延应变薄膜的中间绝缘单斜结构（M2相）中观察到金属链的出现，证明了莫特转变涉及关键库仑相互作用的破坏。通过测量具有分离振动模式的相干光学声子的温度动力学揭示了这一点，这些振动模式源自M2中的两个子结构：一个是由电子-声子（e-ph）相互作用形成的电荷密度波，另一个是具有电子-电子（e-e）关联的等间距绝缘链。
