Surface Plasmon Polaritons and Novel Electromagnetic Modes in Three-Dimensional Dirac Semimetal Films

Oleg Kotov Laboratory of Nanostructure Spectroscopy, Institute for Spectroscopy Russian Academy of Sciences, Moscow, Russia The Center for Fundamental and Applied Research, Dukhov All-Russia Research Institute of Automatics, Moscow, Russia Yurii Lozovik Laboratory of Nanostructure Spectroscopy, Institute for Spectroscopy Russian Academy of Sciences, Moscow, Russia The Center for Fundamental and Applied Research, Dukhov All-Russia Research Institute of Automatics, Moscow, Russia

Recent experiments [1-4] have attracted attention of the researchers to a novel state of quantum matter - three-dimensional (3D) Dirac semimetals (DSs), which can be considered as “3D graphene”. In these experiments very high electron mobility was observed, up to 280,000 cm2/Vs [2], [3], which is comparable to that of the best graphene samples. The fact can be widely used for various applications, particularly, 3D DSs may become candidates for low-loss plasmonic materials. Currently, the best plasmon characteristics were observed in graphene: low losses, long propagation distance, strong filed confinement, high electrostatic gate tunability. Also the existing of unusual TE electromagnetic (EM) waves in graphene was predicted. We investigate how these properties will change due to passing from 2D to 3D Dirac system. Particularly, we calculated the dispersion laws of plasmons and surface plasmon polaritons (SPP) in 3D DS films. We compared these results with those for common metal films and graphene. We predict the existence of novel weakly damped EM modes propagating in the thickness of 3D DS film - the analogue of evanescent TE waves in graphene. We obtain that at frequencies lower than bulk plasma frequency constant (THz and far-IR regions) 3D DS film as a common metal one possesses SPP and at higher frequencies (mid-IR region) it behaves as a dielectric waveguide. These frequency ranges can be tuned by changing the Fermi level of the system. In comparison with metal film SPP in 3D DS one have larger propagation length and stronger field confinement . Moreover, in thin (less than 50nm) 3D DS film SPP field confinement is even stronger than in graphene. All this makes 3D DSs promising materials for plasmonics.

[1] Z. K. Liu et al., Science 343, 864-867 (2014).
[2] S. Borisenko et al., Phys. Rev. Lett. 113, 027603 (2014).
[3] M. Neupane et al., Nature Commun. 5, 3786 (2014).
[4] Z. K. Liu et al., Nature Materials 13, 677 (2014).

oleg.v.kotov@yandex.ru