Unconventional thermal cloak hiding an object outside the cloak

All the thermal cloaks reported in the literature can be used to thermally hide an object inside the cloak. However, a common limitation of this kind of thermal cloaks is that the cloaked object cannot feel the external heat flow since it is located inside the cloak; thus we call these cloaks ``conventional thermal cloaks''. Here we manage to overcome this limitation by exploiting a class of unconventional thermal cloaks that enable the cloaked object to feel the external heat flow. Our finite element simulations in two dimensions show the desired cloaking effect. The underlying mechanism originates from the complementary effect of thermal metamaterials with negative thermal conductivities. This work suggests a different method to design thermal devices where heat conduction can be controlled at will.