  Dynamical Phase transitions (DPTs) describe the abrupt change in the
dynamical properties of open systems when a single control parameter is
slightly modified. Recently we found that this phenomenon is also present in a
simple model of a linear array of metallic nanoparticles (NPs) in the form of a
localized-delocalized DPT. In this work we show how to take advantage of DPTs
in order to design a new kind of plasmonic sensor which should own some unique
characteristics. For example, if it were used as plasmon ruler it would not
follow the so called universal plasmon ruler equation [Nano Letters 2007, 7,
2080-2088], exhibiting instead an on-off switching feature. This basically
means that a signal should only be observed when the control/measured
parameter, i.e. a distance in the case of plasmon rulers, has a very precise
and pre-determined value. Here, we demonstrate their feasibility and unique
characteristics, showing that they combine high sensitivity with this on-off
switching feature in terms of different distances and local dielectric
constants. This property has the potentiality to be used in the design of new
plasmonic devices such as plasmonic circuits activated only under certain
environmental conditions.
