中国地质大学戴志高团队近日研究了非双曲晶体表面上的长程双曲极化子。这一研究成果于2025年7月16日发表在《自然》杂志上。

双曲晶体中的杂化物质-光子激发——以介电常数张量分量为特征的各向异性材料——由于其以双曲极化子形式存在的强光-物质相互作用而引起了大量关注。然而，这些现象仅限于双曲晶体，其光学响应局限于固定的光谱区域，缺乏可调性，从而限制了其更广泛的适用性。

研究组证明了在非双曲型钒酸钇（YVO₄）晶体中双曲型表面声子极化子的出现。利用实空间纳米成像技术结合理论分析，他们在YVO₄晶体表面的非双曲频率范围内可视化了表面声子极化子的双曲波前，其中材料的介电常数张量分量具有相同的负号。

此外，通过从室温到低温水平的温度变化，研究组实现了对极化子色散的原位操纵，实现了从双曲型到准直传输再到椭圆型的拓扑相变过程。这种温控色散工程不仅提供了对极化子拓扑的精确控制，而且还可以调制它们的波长和群速度，显示出卓越的灵敏度以及低损耗、远程传播。这些发现通过消除对双曲晶体的依赖，扩展了双曲纳米光学的领域，为负折射、超透镜、极化化学、集成光子学等领域的应用提供了机会。

附：英文原文

Title: Long-range hyperbolic polaritons on a non-hyperbolic crystal surface

Author: Liu, Lu, Xiong, Langlang, Wang, Chongwu, Bai, Yihua, Ma, Weiliang, Wang, Yupeng, Li, Peining, Li, Guogang, Wang, Qi Jie, Garcia-Vidal, Francisco J., Dai, Zhigao, Hu, Guangwei

Issue&Volume: 2025-07-16

Abstract: Hybridized matter–photon excitations in hyperbolic crystals—anisotropic materials characterized by permittivity tensor components with opposite sign—have attracted substantial attention owing to their strong light–matter interactions in the form of hyperbolic polaritons1,2,3. However, these phenomena have been restricted to hyperbolic crystals, whose optical responses are confined to fixed spectral regions and lack tunability, thereby limiting their broader applicability4,5. Here we demonstrate the emergence of hyperbolic surface phonon polaritons in a non-hyperbolic yttrium vanadate (YVO4) crystal. Using real-space nanoimaging combined with theoretical analyses, we visualize hyperbolic wavefronts of surface phonon polaritons on YVO4 crystal surfaces within its non-hyperbolic frequency range, where the permittivity tensor components of the material have the same negative sign. Furthermore, by varying the temperature from room temperature to cryogenic levels, we realize in situ manipulation of polariton dispersions, enabling a topological transition from hyperbolic to canalization and eventually to the elliptic regime. This temperature-controlled dispersion engineering not only provides precise control over polariton topology but also modulates their wavelength and group velocity, showing remarkable sensitivity alongside low-loss, long-range propagation. These findings extend the realm of hyperbolic nano-optics by removing the reliance on hyperbolic crystals, unlocking opportunities for applications in negative refraction6,7,8,9,10, superlensing11,12, polaritonic chemistry13, integrated photonics14,15,16 and beyond.

DOI: 10.1038/s41586-025-09288-1

Source: https://www.nature.com/articles/s41586-025-09288-1