946 research outputs found
Microscopic dynamics of supercooled liquids from first principles
Glasses are solid materials whose constituent atoms are arranged in a
disordered manner. The transition from a liquid to a glass remains one of the
most poorly understood phenomena in condensed matter physics, and still no
fully microscopic theory exists that can describe the dynamics of supercooled
liquids in a quantitative manner over all relevant time scales. Here we present
such a theoretical framework that yields near-quantitative accuracy for the
time-dependent correlation functions of a supercooled system over a broad
density range. Our approach requires only simple static structural information
as input and is based entirely based on first principles. Owing to this
first-principles nature, the framework offers a unique platform to study the
relation between structure and dynamics in glass-forming matter, and paves the
way towards a systematically correctable and ultimately fully quantitative
theory of microscopic glassy dynamics
Relaxation Patterns in Supercooled Liquids from Generalized Mode-Coupling Theory
The mode-coupling theory of the glass transition treats the dynamics of
supercooled liquids in terms of two-point density correlation functions. Here
we consider a generalized, hierarchical formulation of schematic mode-coupling
equations in which the full basis of multipoint density correlations is taken
into account. By varying the parameters that control the effective
contributions of higher-order correlations, we show that infinite hierarchies
can give rise to both sharp and avoided glass transitions. Moreover, small
changes in the form of the coefficients result in different scaling behaviors
of the structural relaxation time, providing a means to tune the fragility in
glass-forming materials. This demonstrates that the infinite-order construct of
generalized mode-coupling theory constitutes a powerful and unifying framework
for kinetic theories of the glass transition
Conductivity of disordered quantum lattice models at infinite temperature: Many-body localization
We reinvestigate the behavior of the conductivity of several disordered
quantum lattice models at infinite temperature using exact diagonalization.
Contrary to the conclusion drawn in a recent investigation of similar
quantities in identical systems, we find evidence of a localized regime for
strong random fields. We estimate the location of the critical field for the
many-body localization transition for the random-field XXZ spin chain, and
compare our findings with recent investigations in related systems.Comment: 5 pages, 4 figures. Accepted for publication in Phys. Rev.
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