100 research outputs found
Ergodicity breaking transition in a glassy soft sphere system at small but non-zero temperatures
While the glass transition at non-zero temperature seems to be hard to access
for experimental, theoretical, or simulation studies, jamming at zero
temperature has been explored in great detail. It is a widely discussed
question whether this athermal jamming transition is related to the glass
transition. Motivated by the exploration of the energy landscape that has been
successfully used to describe athermal jamming, we introduce a new method to
determine whether the configuration space of a soft sphere system can be
explored within a reasonable timescale or not, i.e., whether the system is
ergodic or effectively non-ergodic. While in case of athermal jamming for a
given random starting configuration only the local energy minimum is
determined, we allow the thermally excited crossing of energy barriers.
Interestingly, we observe that a transition exists where the system becomes
effectively non-ergodic if the density is increased. In the limit of small but
non-zero temperatures the density where the ergodicity breaking transition
occurs approaches a value that is independent of temperature and below the
transition density of athermal jamming. This confirms recent computer
simulation studies where athermal jamming occurs deep inside the glass phase.
In addition, with our method we determined the critical behavior of the
ergodicity breaking transition and show that it is in the universality class of
directed percolation. Therefore, our approach not only makes the transition
from an ergodic to an effectively non-ergodic systems easily accessible and
helps to reveal its universality class but also shows that it is fundamentally
different from athermal jamming.Comment: 20 pages, 7 figures + 3 supplementary figure
Anomalous magnetic response of a quasi-periodic mesoscopic ring in presence of Rashba and Dresselhaus spin-orbit interactions
We investigate the properties of persistent charge current driven by magnetic
flux in a quasi-periodic mesoscopic Fibonacci ring with Rashba and Dresselhaus
spin-orbit interactions. Within a tight-binding framework we work out
individual state currents together with net current based on second-quantized
approach. A significant enhancement of current is observed in presence of
spin-orbit coupling and sometimes it becomes orders of magnitude higher
compared to the spin-orbit interaction free Fibonacci ring. We also establish a
scaling relation of persistent current with ring size, associated with the
Fibonacci generation, from which one can directly estimate current for any
arbitrary flux, even in presence of spin-orbit interaction, without doing
numerical simulation. The present analysis indeed gives a unique opportunity of
determining persistent current and has not been discussed so far.Comment: 10 pages, 16 figures (Accepted for Publication in: The European
Physical Journal B-Condensed Matter and Complex Systems
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