Many topological regions on the Bloch sphere of the spin-1/2 double kicked top

TL;DR

This paper explores the topological regions on the Bloch sphere of the spin-1/2 double kicked top, revealing complex structures with large winding numbers and boundary states, extending previous results from the quantum double kicked rotor.

Contribution

It extends the study of topological phases to the spin-1/2 quantum double kicked top, identifying multiple topological regions and their boundaries characterized by quasienergy states.

Findings

Large winding number regions on the Bloch sphere.

Boundaries host 0 and π quasienergy bound states.

Localization observed at boundaries with specific initial states.

Abstract

Floquet topological systems have been shown to exhibit features not commonly found in conventional topological systems such as topological phases characterized by arbitrarily large winding numbers. This is clearly highlighted in the quantum double kicked rotor coupled to spin-1/2 degrees of freedom [Phys. Rev. A 97, 063603 (2018)] where large winding numbers are achieved by tuning the kick strengths. Here, we extend the results to the spin-1/2 quantum double kicked top and find not only does the system exhibit topological regions with large winding numbers, but a large number of them are needed to fully characterize the topology of the Bloch sphere of the top for general kick strengths. Due to the geometry of the Bloch sphere it is partitioned into regions with different topology and the boundaries separating them are home to 0 and $\pi$ quasienergy bound states. We characterize the regions by comparing local versions of the mean field, quantum and mean chiral displacement winding numbers. We also use a probe state to locate the boundaries by observing localization as the state evolves when it has a large initial overlap with bound states. Finally, we briefly discuss the connections between the spin-1/2 quantum double kicked top and multi-step quantum walks, putting the system in the context of some current experiments in the exploration of topological phases.