arXiv subjects

Holly A. J. Middleton-Spencer

Publications and source records attributed to Holly A. J. Middleton-Spencer.

4 recordsLinked to original sources

arXiv2026

Quantized Transport of Gap Solitons in the Harper-Hofstadter Model

We investigate the dynamics of gap solitons found in the Harper-Hofstadter model with an additional cubic nonlinearity, such as that describing weakly-interacting cold atoms or a Kerr nonlinearity in an optical platform. We find that certain solitons with frequencies deep in the band gap travel with a robust, quantized velocity perpendicular to the applied force and maintain their spatial profile over long timescales. Crucially, this velocity is linearly proportional to the applied force, allowing for arbitrary steering of the nonlinear wavepacket, without breakdown, using only a tunable external force. This quantized transport persists despite a highly non-uniform occupation of the linear Bloch states, and contrasts with solitons near the band edge, which deform and delocalize under the same force. These results point to a robust and highly controllable mechanism for steering nonlinear solitons in experimentally accessible platforms.

physics.optics↗

arXiv2026

Vortex lattices in coupled one-dimensional Bose-Einstein condensates with a synthetic magnetic field

We investigate the mean-field ground states of coupled one-dimensional Bose-Einstein condensates subject to a synthetic magnetic field. The resulting interacting coupled-wire model has one continuous and one discrete spatial direction, providing a controlled way to interpolate between the physics of few-leg ladders and extended vortex lattices. For two wires, we study the vortex-like, biased-density, and Meissner-like states, exploring how the finite longitudinal size of the system modifies the transitions between them. Increasing the number of wires, the ground state evolves towards an extended vortex lattice. We find numerically that periodic boundary conditions in the discrete direction can favour staggered arrays of like-signed vortices resembling an Abrikosov lattice, while open boundaries in small finite-size systems confine the vortices into rows near the centre of the synthetic direction. Our results explore how finite size effects and boundary conditions govern the emergence and spatial organisation of vortices in continuous-discrete quantum fluids, with relevance to future experiments in tunnel-coupled atomic wires or with synthetic dimensions.

cond-mat.quant-gas↗

arXiv2026

Probing topological edge states in a molecular synthetic dimension

Engineering synthetic dimensions, where the physics of additional spatial dimensions is simulated within the internal states of a quantum system, allows the realisation of phenomena not otherwise accessible in experiments. Ultracold ground-state polar molecules are an ideal platform to encode synthetic dimensions, offering access to large Hilbert spaces of long-lived internal states associated with the rotational and hyperfine degrees of freedom, that can be coupled together with microwave fields to simulate tunnelling. Here, to benchmark the advantages of ultracold molecules, we encode a 1D synthetic lattice in the rotational states of ultracold RbCs molecules and use it to investigate the well-known Su-Schrieffer-Heeger (SSH) model, a minimal model displaying topological properties. To probe the system, we perform spectroscopy using an auxiliary rotational state and study the time dynamics after deterministic state preparation. We demonstrate long coherence times, typically ~500 times the lattice tunnelling period, even for a synthetic lattice using 8 rotational states. Observations of dynamics at long times with full site-resolved readout of the synthetic dimension allow us to test the effects of chiral and non-chiral perturbations on the topologically protected edge states. Our work lays the foundation for further quantum simulations using the rich internal structure of molecules, including dipolar string phases in interacting samples of molecules, and adiabatic state preparation of many-body Hamiltonians.

physics.atom-ph↗

arXiv2026

Phases of interacting bosons in a hybrid Harper-Hofstadter system with a synthetic dimension of harmonic trap states

Synthetic dimensions are a powerful tool for engineering desired quantum systems, based on coupling together sets of states and reinterpreting these as lattice sites along an artificial dimension. Recently, a synthetic dimension of harmonic trap states has been successfully implemented in an ultracold atom experiment, opening the way for future realizations in this platform of topological lattice models, such as hybrid Harper-Hofstadter (HH) systems, which have one real and one synthetic dimension. However, unlike conventional systems, inter-particle interactions along a synthetic dimension of harmonic trap states are inhomogeneous, long-ranged and non-state-preserving. Therefore, this setup provides a natural platform for the exploration of the interplay between long range interactions (including correlated pair tunneling) and magnetic effects. In this paper, we set out to numerically study the effect of such interactions on both a hybrid two-legged HH ladder and a 2D HH model. In the former, we find variants of vortex and Meissner phases familiar from conventional models, while in the latter, we observe the emergence, in small finite systems, of unusual ground states, including a ``Meissner stripe" state, which combines counter-propagating Meissner-like currents with strong density variations. This opens up interesting questions, including about the nature of strongly-correlated states that would emerge in such a platform.

cond-mat.quant-gas↗