CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology , Beijing 100190 , P.R. China.
School of Nanoscience and Technology , University of Chinese Academy of Sciences , Beijing 100049 , P.R. China.
Nano Lett. 2019 Mar 13;19(3):1805-1813. doi: 10.1021/acs.nanolett.8b04855. Epub 2019 Feb 25.
Two-dimensional layered 1 T-TaS exhibits rich charge-density-wave (CDW) states with distinct electronic structures and physical properties, leading to broad potential applications, such as phase-transition memories, electrical oscillators and photodetectors. Besides the various CDW ground states at different temperatures, multiple intermediate phases in 1 T-TaS have been observed by applying optical and electrical stimulations. Here, we investigated the electric-field-driven multistate CDW phase transition by Raman spectroscopy and voltage oscillations in 1 T-TaS. Strong correlation was observed between electrical conductivity and intensity of fold-back acoustic and optical phonon modes in 1 T-TaS. This indicates that the multistate transitions arise from serial transitions, from the nearly commensurate (NC) CDW phase to out-of-equilibrium intermediate states, and finally to the incommensurate (IC) CDW phase. The dynamics of phase transition under an electric field was investigated. As the electrical field increased, the dwell time of different CDW states changed. At lower temperatures, the multistate oscillations disappeared because of higher-energy barriers between the intermediate phases and/or lower thermal excitation energies at lower temperatures.
二维层状 1T-TaS 具有丰富的电荷密度波（CDW）态，具有独特的电子结构和物理性质，因此具有广泛的潜在应用，例如相变存储器、电振荡器和光电探测器。除了在不同温度下具有各种 CDW 基态外，通过施加光学和电学刺激，已经观察到 1T-TaS 中的多个中间相。在这里，我们通过拉曼光谱和 1T-TaS 中的电压振荡研究了电场驱动的多态 CDW 相转变。在 1T-TaS 中，电导率与折叠背式声子和光学声子模式的强度之间观察到很强的相关性。这表明多态跃迁来自于连续跃迁，从近乎协调（NC）CDW 相到非平衡中间相，最后到非协调（IC）CDW 相。研究了电场下相转变的动力学。随着电场的增加，不同 CDW 态的停留时间发生了变化。在较低的温度下，由于中间相之间的能量势垒较高和/或较低的低温热激发能，多态振荡消失了。
