Interaction-enabled metal-insulator phase transition in a driven quantum gas

arXiv:2605.22449 · arXiv: 2605.22449

License: CC BY 4.0.

Abstract

Particle transport and energy flow are central to a wide range of phenomena in the natural sciences. While interactions generically promote ergodicity and diffusion, quantum interference can arrest transport, defying classical expectations. Here, we experimentally investigate their interplay in a periodically driven 3D quantum gas with tunable interactions. Strikingly, we find a sharp dynamical boundary separating localization from diffusive energy absorption. By tuning the driving amplitude and interaction strength, we map the localization-delocalization phase diagram and characterize this boundary via finite-time scaling. On the insulating side, we observe many-body dynamical localization (MBDL) featuring arrested momentum-space transport. Transport becomes subdiffusive near the boundary and diffusive in the delocalized regime, yielding a metal-insulator transition that we interpret as localization in many-body Hilbert space. Our results exemplify an interaction-enabled dynamical phase transition in a closed Floquet many-body system, and clarify how coherence and interactions jointly govern the quantum-to-classical transition.

Figures

12 panels with data across 5 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

• panel (b): Waterfall of the momentum distribution against momentum $k/k_L$ and kick number $N_p$, eleven curves from 0 to 1000 kicks, at $\kappa = 0.75$ and $a_s = 220\,a_0$. Heights are $\log_{10} n(k)$, as printed; where the deposited $n(k)$ is zero or below there is no logarithm and the cell is left empty. The hosted heights run about 0.1 decade above the printed ones. data.csv
• panel (c): Waterfall of the momentum distribution against momentum $k/k_L$ and kick number $N_p$, eleven curves from 0 to 1000 kicks, at $\kappa = 1.5$ and $a_s = 775\,a_0$. Heights are $\log_{10} n(k)$, as printed; where the deposited $n(k)$ is zero or below there is no logarithm and the cell is left empty. The hosted heights run about 0.1 decade above the printed ones. data.csv
• panel (d): Energy proxy $E$ against kick number $N_p$ at $\kappa = 0.75$ for three scattering lengths, $a_s = 0$, 220 and $775\,a_0$. Each point is the average of three realizations, with its error bar. The dashed line is the linear fit to the $775\,a_0$ series. data.csv
• panel (e): Energy proxy $E$ against kick number $N_p$ at $\kappa = 1.5$ for three scattering lengths, $a_s = 0$, 220 and $775\,a_0$. Each point is the average of three realizations, with its error bar. The dashed lines are the linear fits to the 220 and $775\,a_0$ series. The $775\,a_0$ series is shown up to $E \approx 300$; the printed axis stops at 150 and leaves out five of its points. data.csv

Fig. 2

The available data cannot be matched to this figure unambiguously. The figure is shown in the paper PDF. Page 3 of the PDF.

Fig. 3

• panel (1): Energy proxy $E$ against kick number $N_p$ at $\kappa = 0.75$, for $a_s$ held at $220\,a_0$, held at $775\,a_0$, ramped up from 220 to $775\,a_0$ and ramped down from 775 to $220\,a_0$ at $N_p = 400$, with error bars. Dotted lines are linear fits to the two held series, dashed lines to the two ramps. The two dashed arrows of the printed panel are not drawn. data.csv
• panel (1-inset-1): Top inset of the printed panel, case A (the ramp up): momentum distribution $n(k)$ against $k/k_L$ at $N_p = 800$ and $N_p = 1200$, each normalised to a peak of one. data.csv
• panel (1-inset-2): Bottom inset of the printed panel, case B (the ramp down): momentum distribution $n(k)$ against $k/k_L$ at $N_p = 800$ and $N_p = 1200$, each normalised to a peak of one. data.csv

Fig. 4

• panel (a): In-situ spatial density $\rho(z)$ against kick number $N_p$ and position $z$ ($\mu$m), for the MBDL case, $\kappa = 0.75$ and $a_s = 220\,a_0$. The numerical-simulation inset of the printed panel is not shown. data.csv
• panel (b): In-situ spatial density $\rho(z)$ against kick number $N_p$ and position $z$ ($\mu$m), for the delocalized case, $\kappa = 1.5$ and $a_s = 775\,a_0$. The numerical-simulation inset and the red dashed guide lines of the printed panel are not shown. data.csv
• panel (c): In-situ spatial density $\rho(z)$ against kick number $N_p$ and position $z$ ($\mu$m), for the MBDL case, $\kappa = 0.75$ and $a_s = 220\,a_0$, with the kicking stopped at $N_p = 300$. The numerical-simulation inset and the dash-dotted guide lines of the printed panel are not shown. data.csv

Fig. 5

• panel (1): Width of the central peak $\sigma_z$ ($\mu$m) against hold time $t_{\mathrm{hold}}$ (ms) after the scattering length is quenched to zero, for $N_p = 0$, 1, 100, 500 and 1000 kicks, with an unquenched cloud ($N_p = 1000$) for comparison. Shaded bands are the standard deviation over three repetitions; dashed curves are the authors' sinusoidal fits to the quenched series. data.csv

Fig. 6

• panel (1): Energy proxy $E$ against kick number $N_p$ at the critical kick strength $\kappa_c = 1.16$, with error bars. The red curve is the shifted power-law fit $E(N_p) = A(N_p - N_p^{*})^{2/3}$ to the late-time data, $N_p > 500$. data.csv

Cite

Camilo Cantillano, Karthick Ramanathan, Zekai Chen, Ang Yang, Emilio Aguilera-Valdes, Lei Ying, Manuele Landini, Hanns-Christoph Nägerl, Yanliang Guo. Interaction-enabled metal-insulator phase transition in a driven quantum gas. arXiv:2605.22449

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