Sub-wavelength optical lattices

Speaker : Prof. Gediminas Juzeliūnas (Vilnius University)

Abstract :
Traditionally, optical lattices are created by interfering two or more light beams, so that atoms are
trapped at minima or maxima of the emerging interference pattern depending on the sign of the
atomic polarizability [1]. The characteristic distances over which such lattice potentials change are
limited by diffraction and thus cannot be smaller than a half of the optical wavelength λ. The
diffraction limitation can be overcome and subwavelength lattices can be created using coherent
coupling between atomic internal states [2-8]. In particular, recent experiments demonstrated deeply
subwavelength lattices using atoms with N internal states Raman-coupled with lasers of wavelength λ
[7]. The resulting lattice has an N times smaller periodicity compared to the usual λ/2 periodicity of an
optical lattice.
In the present talk we will discuss various ways to produce subwavelength lattices and effects of the
periodic driving on these lattices. In particular, we will present our recent work on periodic driving of
subwavelength lattices leading to formation of a pair of coupled subwavelength Rice--Mele chains
operating as a novel topological charge pump [8].

[1] I. Bloch, Nature Physics 1, 23 (2005).
[2] M. Łącki et al., Phys. Rev. Lett. 117, 233001 (2016).
[3] F. Jendrzejewski et al., Phys. Rev. A 94, 063422 (2016).
[4] Y. Wang et al, Phys. Rev. Lett. 120, 083601 (2018).
[5] E. Gvozdiovas, P. Račkauskas, G. Juzeliūnas, SciPost Phys. 11, 100 (2021).
[6] P. Kubala, J. Zakrzewski and M. Łącki, Phys. Rev. A 104, 053312 (2021).
[7] R. P. Anderson et al, Physical Review Research 2, 013149 (2020).
[8] D. Burba, M. Račiūnas, I. B. Spielman and G. Juzeliūnas, arXiv:2210.05515.