Reentrance in an active glass mixture

Abstract

Active matter, whose motion is driven, and glasses, whose dynamics are arrested, seem to lie at opposite ends of the spectrum in nonequilibrium systems. In spite of this, both classes of systems exhibit a multitude of stable states that are dynamically isolated from one another. While this defining characteristic is held in common, its origin is different in each case: for active systems, the irreversible driving forces can produce dynamically frozen states, while glassy systems vitrify when they get kinetically trapped on a rugged free energy landscape. In a mixture of active and glassy particles, the interplay between these two tendencies leads to novel phenomenology. We demonstrate this with a spin glass model that we generalize to include an active component. In the absence of a ferromagnetic bias, we find that the spin glass transition temperature depresses with the active fraction, consistent with what has been observed for fully active glassy systems. When a bias does exist, however, a new type of transition becomes possible: the system can be cooled out of the glassy phase. This unusual phenomenon, known as reentrance, has been observed before in a limited number of colloidal and micellar systems, but it has not yet been observed in active glass mixtures. Using low order perturbation theory, we study the origin of this reentrance and, based on the physical picture that results, suggest how our predictions might be measured experimentally.

Mode-Coupling Theory of the Glass Transition: A Primer

“…During the last decade, numerous synthetic active systems have also become available [80], spurring the development of theoretical approaches to describe the emergent behavior in these non-equilibrium materials. In particular, it was found that dense active matter can also exhibit properties of supercooled liquids and vitrifying colloidal suspensions [6,8,11,[81][82][83][84][85][86][87][88][89][90], including slow structural relaxation, dynamic heterogeneity, varying degrees of fragility, and the ultimate formation of a kinetically arrested, amorphous solid state.…”

How active forces influence nonequilibrium glass transitions

“…Nonequilibrium glass transitions have recently emerged as a new type of dynamic arrest occurring in particle systems driven out of equilibrium by active forces [1,2]. The initial theoretical interpretation, based on the analysis of simple glass models driven by active forces [3], has been confirmed in several computer simulations of more realistic active matter models [1,[4][5][6][7][8][9][10][11][12][13][14]49]. A number of alternative theoretical approaches have now been proposed to describe this phenomenon [15][16][17].…”

Aging and rejuvenation of active matter under topological constraints

“…Examples of living active matter are found on all length scales, from microscopic motile bacteria to macroscopic flocks of birds, and also numerous synthetic active materials have recently become available [5]. The spatiotemporal dynamics exhibited by such systems range from swarming and giant number fluctuations [6, 7] to low-Reynolds-number turbulence [8][9][10][11] and motility-induced phase separation [12][13][14][15], illustrating the rich collective behavior that emerges from the nonequilibrium energy dissipation and active self-motility at the single-particle level.It was recently found that sufficiently dense assemblies of active matter can also exhibit hallmarks of glassy dynamics [16][17][18][19][20][21][22][23][24][25][26][27][28], including slow relaxation, dynamic heterogeneity, and ultimate kinetic arrest-akin to the behavior observed in non-active supercooled liquids and dense colloidal suspensions [29]. For passive systems, the process of glass formation has been widely studied over the last few decades, resulting in multiple compelling theoretical scenarios for the conventional glass transition [29][30][31].…”