Lecturer: Dr. Yoav Lahini
Affiliation: Department of physics,
Massachusetts Institute of Technology - MIT
Abstract:
Most everyday materials can be described by a
set of numbers that describe their properties – a
resistor for example is described by its
resistance, a number that is useful in predicting
how much current will flow through it under a
given voltage. Some materials however, lack this
basic characteristic. Under constant external
conditions, their properties can change over
many time scales, from fractions of seconds to
weeks and even years, without showing any sign
of reaching equilibrium. Such behavior is
exhibited in a strikingly similar way by very
different systems, from materials such as
polymers and glass to properties of interfaces
leading to friction and even earthquakes.
Perhaps the only common attribute to all this
systems is that they are disordered. Yet, in spite
of many studies that have been conducted on
these recurring motifs across a broad range of
systems, identifying the mechanisms underlying
the unusual out-of-equilibrium dynamics of
disordered systems remains an outstanding
problem in condensed matter physics.
Here, I will describe several disordered soft-
matter systems that exhibit a similar repertoire of
far-from-equilibrium behavior, including
logarithmic relaxation and the ability to hold a
memory of previous conditions that can last for
hours. At the same time, each one of these
systems offers a way to track the evolution of the
internal structure, presenting an opportunity to
reveal and compare mechanisms across different
systems.