Monu Bhartiya | Searcharxiv

arXiv2026

Localization with Hopping Disorder in Quasi-periodic Synthetic Momentum Lattice

Lattice quasi-periodicity is easily realized with ultracold atoms in optical lattices and has been used to study delocalization-localization transition at low dimensions. Models with true disorder, however, remains largely unrealized in experiments. Here, using Bose-Einstein Condensate of ${^{87}{\text{Rb}}}$ atoms, we realize a Generalized Aubry-André (GAA) chain with added hopping disorder in a Momentum Space Lattice (MSL) via multiple Bragg diffractions. Unlike real space lattice simulators, MSL allows simulations of arbitrary disorder configurations and control over spatial disorder correlations. Uncorrelated hopping disorder added to the AA model enhances localization in all phases, smoothening the transition into a crossover between weakly and strongly localized regimes. On the other hand, numerical analysis shows that, spatially correlated hopping disorder induces partial delocalization of localized states in the vicinity of strong hopping bonds. Over a range of disorder strengths and correlations, the experimental results agree quantitatively with the numerical simulation of the dynamics in MSL. Ability of the platform to resolve correlation-dependent dynamical features in dynamics reflects the precision achieved in the realization. Our results demonstrate MSL as a viable platform for studying general disordered quantum systems beyond quasiperiodic systems.

cond-mat.quant-gas↗

arXiv2025

Evaporative cooling by pulse width modulation (PWM) of optical dipole traps

We introduce a method for cooling atoms in an optical dipole trap using pulse-width modulation (PWM) technique, without reducing the laser power of the dipole trap. The PWM technique involves digital modulation of the trap at a fixed frequency. The effective time-averaged dipole potential is lowered by adjusting the duty cycle of the modulation, thereby implementing evaporative cooling. We show that, this technique effectively reduces temperature and enhances phase space density. A comparison with the standard method of evaporative cooling has also been made. Apart from the atom loss due to reduction of the effective trapping potential, we observe an additional loss channel originating from the lack of trapping potential during the trap off time. This atom loss is observed at different modulation frequencies which are an order of magnitude higher compared to trapping frequency of dipole trap. The PWM technique provides an alternative to traditional evaporative cooling in scenarios where it is preferred that the laser power of the trap should be constant.

physics.atom-ph↗