arXiv subjects

Jack Featherstone

Publications and source records attributed to Jack Featherstone.

3 recordsLinked to original sources

arXiv2026

Incoherent dark excitons extend Floquet-like physics across time and momentum

Floquet phenomena - where a coherent, time-periodic drive hybridizes the conduction band with energy-replicated copies of the valence band - have been demonstrated with intense optical fields and, more recently, other bosonic excitations. However, within mean-field approximations and the current understanding of Floquet phenomena, these effects survive only for the coherence time of the drive, limiting practical use and current demonstrations to the sub-picosecond regime. Here, consistent with recent theoretical predictions beyond the mean-field picture, using time- and angle-resolved photoemission spectroscopy in WSe$_2$/MoS$_2$ heterostructures, we show that incoherent, dense populations of dark interlayer excitons hybridize the conduction band with energy-replicated copies of the valence band, mimicking Floquet-like phenomena - now persisting for nearly a nanosecond. With increasing interlayer exciton density, the valence band and its replica evolve from an inverted-parabolic to a Mexican-hat dispersion, a signature of the predicted non-zero static coupling that hybridizes the bands and scales linearly with the exciton density. By tuning twist angle, we further show that dark excitons with net momentum create replicas that hybridize with bands offset not just in energy but also in momentum, providing another powerful degree of freedom beyond conventional Floquet engineering. These results establish a robust, long-lived route to engineering electronic states, beyond a coherent, zero-momentum drive.

cond-mat.mes-hall↗

arXiv2026

Stochastic modeling of long-legged ant A. gracilipes locomotion in laboratory experiments

Stochastic modeling of movement behavior provides a valuable way to understand how complex motion can be generated from relatively simple building blocks. Ants demonstrate sophisticated social behavior ranging from foraging to nest relocation; while emphasis is often placed on the communication methods used to synchronize individuals, the movement paradigms of those individuals are of tantamount importance. Here, we apply a stochastic modeling approach to better understand the movement of isolated long-legged ant (A. gracilipes) specimens, informed by extensive laboratory tracking experiments. We find that a combination of active Brownian and run-and-tumble models reproduces the trajectory statistics observed in experiments, both qualitatively and quantitatively. We identify reproducible probability distributions for the turn angles, run times, and waiting times across specimens, and find good agreement between analytical predictions and quantities empirically measured from the trajectories. Having such a model allows for a better understanding and predictions of movement ecology from both simulations and analytics, and even can give insight into the underlying generative mechanisms of motion and the ants' sensory systems.

q-bio.QM↗

arXiv2021

Stick-slip dynamics in penetration experiments on simulated regolith

The surfaces of many planetary bodies, including asteroids and small moons, are covered with dust to pebble-sized regolith held weakly to the surface by gravity and contact forces. Understanding the reaction of regolith to an external perturbation will allow for instruments, including sensors and anchoring mechanisms for use on such surfaces, to implement optimized design principles. We analyze the behavior of a flexible probe inserted into loose regolith simulant as a function of probe speed and ambient gravitational acceleration to explore the relevant dynamics. The EMPANADA experiment (Ejecta-Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids) flew on several parabolic flights. It employs a classic granular physics technique, photoelasticity, to quantify the dynamics of a flexible probe during its insertion into a system of bi-disperse, cm-sized model grains. We identify the force-chain structure throughout the system during probe insertion at a variety of speeds and for four different levels of gravity: terrestrial, martian, lunar, and microgravity. We identify discrete, stick-slip failure events that increase in frequency as a function of the gravitational acceleration. In microgravity environments, stick-slip behaviors are negligible, and we find that faster probe insertion can suppress stick-slip behaviors where they are present. We conclude that the mechanical response of regolith on rubble pile asteroids is likely quite distinct from that found on larger planetary objects, and scaling terrestrial experiments to microgravity conditions may not capture the full physical dynamics.

astro-ph.EP↗