  Recently, considerable attention has been focused on the transformation
optics and metamaterial due to their fascinating phenomena and potential
applications. Concentrator is one of the most representative ones, which
however is limited in single physical domain. Here we propose and give the
experimental demonstration of bifunctional concentrator that can concentrate
electric and thermal fields into a given region simultaneously while keeping
the external fields undistorted. Fan-shaped structure composed of alternating
wedges made of two kinds of natural materials is proposed to achieve this goal.
The simulation and experimental results show good agreement, thereby confirming
the feasibility of our scheme.
