Synthetic magnetic field for dark state ultracold atoms

Session Information

Location: amf. P7 | "Gheorghe Asachi" Technical University of Iași (TUIAȘI)
Day: 2. Tuesday 16
Time: 08:50-09:00
Chairperson: N/A

Presentation Details

Presentation Type: Poster presentation
Title: Synthetic magnetic field for dark state ultracold atoms
Abstract: The quantum-mechanical motion of a charged particle in a homogeneous magnetic field is characterized by degenerate Landau levels, which play an essential role in the integer and fractional Quantum Hall effects and their underlying topological properties [1]. This degeneracy generally disappears when the magnetic field becomes inhomogeneous. However, Aharonov and Casher showed that for electrons with spin aligned along the magnetic field the ground state remains degenerate even in a non-homogeneous magnetic field [2]. Recently, similar situations have been identified in the adiabatic motion of quantum particles, such as valence band holes in bilayer systems [3] and ultracold atoms dressed by laser fields [4,5]. In these systems, geometric scalar and vector potentials give rise to an effective magnetic field with nontrivial geometric and topological structure. By properly choosing system parameters, this field can satisfy the Aharonov–Casher (AC) condition [3,4], preserving the degeneracy of the lowest Landau level and enabling the realization of topologically protected states, which is important for simulating the fractional Quantum Hall effect.

In this work, we provide a general framework for achieving the AC condition for the adiabatic motion of dark-state atoms in the Λ-type atom–light coupling scheme. This is accomplished by constructing the laser fields from properly chosen superpositions of plane waves. We further analyze configurations involving three, four, and six symmetrically distributed plane waves, as well as quasicrystalline structures formed by five waves. Small deviations from perfect tuning produce narrow subwavelength peaks of strong magnetic field and scalar potential, compensated by a smooth background field of opposite sign, resulting in zero total flux per unit cell. As these peaks are sufficiently narrow, their influence is minimal, and the lowest Landau level remains nearly flat while retaining its topological character.

[1] Zyun F. Ezawa. QUANTUM HALL EFFECTS. Number 0. WORLD SCIENTIFIC, 2026/02/06 2011.
[2] Y. Aharonov and A. Casher. Ground state of a spin-charged particle in a
two-dimensional magnetic field. Phys. Rev. A, 19:2461–2462, Jun 1979.
[3] Jingtian Shi, Nicolás Morales-Durán, Eslam Khalaf, and A. H. MacDonald.
Adiabatic approximation and aharonov-casher bands in twisted homobilayer
transition metal dichalcogenides. Phys. Rev. B, 110:035130, Jul 2024.
[4] Ophelia Evelyn Sommer and Nigel R. Cooper. Ideal optical flux lattices,
2025.
[5] D. Burba and G. Juzeliūnas. Two dimensional sub-wavelength topological dark state lattices. Phys. Rev. Research 7, 043090, 2025.

Presenter

Mr Dominykas Borodinas
Vilnius University | Lithuania

Authors

1. Borodinas, Dominykas | Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania
2. Burba, Domantas | Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania
3. Juzeliūnas, Gediminas | Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania