Recently, Zhou Yixi, a postdoctoral fellow at the Department of Physics of Capital Normal University, and Alexey Kuzmanko of the University of GenevaProfessor Kuzmenko et al. published a paper entitled "Thermal and electrostatic tuning of surface phonon-polaritons in laalo3 srtio3" in the well-known academic journal Nature Communications heterostructures**. This achievement realizes the precise electrical control of phonon polaritons in lanthanum aluminate-strontium titanate heterojunction at low temperature, which is conducive to the miniaturization and integration of nano-optoelectronic devices in the future.
Phonon polaritons are quasiparticles produced by the collective oscillation coupling of photons and optical phonons, which have the properties of semi-light and semi-matter, and have a wide range of application potential in biosensing, thermal energy control, and sub-diffraction imaging because of their strong light-matter interaction and excellent light field compression ability. However, the properties of phonon polaritons depend on the intrinsic properties in the crystal (lattice vibration, etc.), so their propagation behavior is extremely difficult to control and mainly exists in the mid-infrared band, which hinders its application in many fields. The results show that strontium titanate, as a typical class of perovskite oxides, not only supports the phonon polariton mode in the wide spectral frequency range from the mid-infrared to the far infrared band, but also has a two-dimensional electron gas at the heterojunction interface formed with other insulating oxides (the properties can be electrically controlled), so it is considered to be a promising phonon polariton material.
In this paper, for the first time, the real-space imaging of strontium titanate (Fig. 1) and lanthanum aluminate strontium titanate heterojunction with long-range propagation phonon polaritons is achieved at low temperature (15 Kelvin). On this basis, the researchers further realized the temperature and electrical control of the initial frequency of the phonon polaritons, revealing the underlying physical mechanisms (due to the electron-phonon interaction and the change of carrier concentration in the two-dimensional electron gas generated at the heterojunction interface, respectively). This work proves that the oxide interface can be used as a new platform to connect traditional electronics and nanophotonics, and provides an idea for nanoscale electro-optical modulation and the design and fabrication of nano-optoelectronic devices. At the same time, the dual-boundary interferometry method developed in this work effectively solves the problem of uncertainty of the geometric size of the illumination source that is common in the previous near-field optical imaging experiments.
In recent years, through the implementation of policies such as recruiting teachers for postdoctoral studies, the university has continuously strengthened the training and construction of young teachers, encouraged high-quality cooperation at home and abroad, strengthened interdisciplinary integration, and continued to work hard to improve the overall scientific research level and international academic influence of Capital Normal University.
*Links:*: Department of Physics, Personnel Office;Author: Li Zhipeng, Sun Rui;Editors on duty: Wang Yijie, Yu Qianyu, Mei Lanzi;Editor in charge: Ha Jingqi).