二氧化钒(VO2) 是一种典型的强关联电子材料, 当达到相变阈值时, 会可逆地从绝缘单斜相转变到金属金红石相, 这种相变主要通过温度、光照、电场、磁场、应力等激励条件激发。相突变可在亚皮秒时间尺度内发生, 并会伴随着光学透过率、折射率和磁化率等特性的显著变化，其中相变前后电阻率会发生 3～5 个数量级的变化, 这使得 VO2 在智能节能窗、光电探测、光电存储、光开关等领域有着重要的应用前景。首先介绍了 VO2 的相变机制, 主要有电子关联驱动、晶格结构驱动以及两者共同驱动, 接着重点介绍了利用超快时间分辨技术, 尤其是太赫兹时域光谱技术, 来研究 VO2 薄膜的相变动力学过程, 最后, 介绍了基于 VO2 薄膜的太赫兹调制器、太赫兹滤波器、太赫兹开关等领域的应用研究。

Vanadium dioxide(VO2) is an archetypal strongly correlated-electron material. When the phase transition threshold is reached, there will be a reversible transition from the insulating monoclinic phase to the metallic rutile phase for VO2. The transition can be induced mainly by thermal, optical, electrical, magnetic field, and strain. The abrupt change of VO2 phase can occur in subpicosecond time scales, along with the significant change of optical reflectivity, refractive index, magnetic susceptibility, and other physical quantities. In particular, the resistivity of VO2 will change in three to five orders of magnitude before and after the phase change, which makes VO2 has great application prospects in the fields of intelligent energy-saving windows, photoelectric detection, photoelectric storage, optical switches, and other fields. This review first describes the phase transitions mechanism of VO2, which is driven by the electron correlation or the lattice structure alone or both. Then it focuses on employing ultrafast time-resolved techniques, particularly terahertz time-domain spectroscopy techniques, to study the phase transition dynamics process of VO2 thin films. Finally, the application research of terahertz modulators, terahertz filters, terahertz switches, and other devices based on VO2 thin films are introduced.