The quantum kicked rotor (QKR) is a system used to explore quantum chaos, which is extensively studied theoretically and experimentally. The QKR also has many flavours such as the single kicked rotor revealing localisation, delocalisation and anti-resonant behaviours. Moreover, it has the ability to expand to higher dimensions by the modulation of the kick strength with incommensurate frequencies resulting in the quantum double kicked rotor. Particular configurations of the QKR have exhibited Floquet topological phases (Hofstadter butterfly spectrum [1]) showing the expansive nature of the system. Cold atoms systems provide the experimental basis to study the QKR. The cold atoms are kicked by far off resonant short laser pulses and the population distribution on the external momentum states provide a measure of the system energy. The ability to introduce the internal degree of freedom has resulted in the quantum double kicked rotor with spin-1/2 degree of freedom. This system shows rich topological phases due to the interplay between internal and external degrees of freedom [2]. These topologies are characterised by two winding numbers, which are detected by measuring the mean chiral displacement in momentum space and enables exploration of topological phenomena equivalent to the quantum hall effect (QHE). We are experimentally implementing a quantum double kicked rotor with spin 1/2 degree of freedom using the ground state hyperfine levels of a quantum degenerate gas of Rb-87 atoms. Here we describe progress towards spin-orbit coupling and the realisation of topological states in this system.
References
[1] D. R. Hofstadter, Phys. Rev. B 14, 2239 (1976)
[2] L. Zhou et al, Phys. Rev. A 97, 063603 (2018)
About the presenter
Anushka Thenuwara is a Research Fellow at Monash University with CI Kris Helmerson. He investigates topological states in the delta-kicked particle system with spin-orbit coupling, as part of FLEET’s Research Theme 2, Exciton Superfluids.