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Simulating gauge field physics using ultracold atoms
Simulating gauge field physics using ultracold atoms
Although gauge fields, e.g., electromagnetic fields, are ubiquitous, simulation with tabletop ultracold atom experiments offers unprecedented controllability. The first artificial magnetic field experiments using cold atoms exploited the equivalence between the Lorentz force in a uniform magnetic field and the Coriolis force in a spatially rotating frame. This approach, however, was limited to study weak fields.
Subwavelength adiabatic optical lattice
Subwavelength adiabatic optical lattice
In the above Raman coupling scheme, each spin flip is associated with absorbing a photon from one laser beam and emitting it to the other, which is accompanied by a two-photon-recoil momentum transfer. Such interaction locks the spin and momentum, realizing 1D SOC--equal contribution from Rashba and Dresselhaus SOC.
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R. P. Anderson, D. Trypogeorgos, A Valdés-Curiel, Q.-Y. Liang, J. Tao, M. Zhao, T. Andrijauskas, G. Juzeli nas & I. B. Spielman
Realization of a deeply subwavelength adiabatic optical lattice. Physical Review Research 2, 013149 (2020)
Rashba spin-orbit coupling (SOC)
Rashba spin-orbit coupling (SOC)
Rashba SOC is present for 2D free electrons in the presence of a uniform perpendicular electric field, such as in asymmetric semiconductor heterostructures. Atomic systems with Rashba SOC were predicted to possess interesting but fragile many-body states. In this context, we realized Rashba SOC in the same hyperfine manifold that reduced losses from spin-relaxation collisions and increased stability against environmental fluctuations by using synthetic clock states. We characterized this system using both spectroscopy and quantum state tomography. This allowed us to measure the dispersion branches and directly observe the single Dirac point linking the lowest two branches as well as to reconstruct the Berry connection to derive the associated Chern numbers.
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A Valdés-Curiel, D. Trypogeorgos, Q.-Y. Liang, R. P. Anderson & I. B. Spielman
Topological features without a lattice in Rashba spin-orbit coupled atoms. arXiv preprint arXiv:1907.08637 (2019). Nat. Commun. 12, 593 (2021)
Rashba SOC as in asymmetric semiconductor heterostructures
Coherence and decoherence in the Harper-Hofstadter model
Coherence and decoherence in the Harper-Hofstadter model
Realizing the Harper-Hofstadter model using synthetic magnetic fields has distinct advantages, all of which are utilized in this project:
Single-site resolution. Single-site resolution along the synthetic dimension comes with no complex imaging system, allowing us to keep track of the atom populations in each synthetic site.
Boundary condition control. The boundary condition of the synthetic dimension is controlled by laser coupling. We easily switched between the tube and ribbon geometries to compare the cases with and without interferometry.
Asymmetric geometry. The number of synthetic lattice sites is much shorter than that of optical lattice sites, forming a highly-asymmetric 2D lattice space. As the the number of synthetic lattice sites dictates the time scale of the interference onset, if it were comparable to the optical lattice extent, we would not have observed the interference in our experimental probing window.
Full flux tuning range. Combining laser beam geometry and wavelength control, we could sweep the flux per lattice plaquette the full range--from zero to one magnetic flux quantum. This would require an intangibly large magnetic field on the order of 104 T by applying a real magnetic field to a typical crystal lattice. It is worth noting that an alternative proven method is to instead use Moiré lattices.
Ref
Q.-Y. Liang, D. Trypogeorgos, A Valdés-Curiel, J. Tao, M. Zhao & I. B. Spielman
Coherence and decoherence in the Harper-Hofstadter model. arXiv preprint arXiv:2012.02202 (2020). Phys. Rev. Research 3, 023058 (2021).
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