The macroscopic control of ubiquitous heat flow remains poorly explored due to the lack of a fundamental theoretical method. Here, by establishing temperature-dependent transformation thermotics for treating materials whose conductivity depends on temperature, we show analytical and simulation evidence for switchable thermal cloaking and a macroscopic thermal diode based on the cloaking. The latter allows heat flow in one direction but prohibits the flow in the opposite direction, which is also confirmed by our experiments. Our results suggest that the temperaturedependent transformation thermotics could be a fundamental theoretical method for achieving macroscopic heat rectification, and provide guidance both for macroscopic control of heat flow and for the design of the counterparts of switchable thermal cloaks or macroscopic thermal diodes in other fields like seismology, acoustics, electromagnetics, or matter waves.

We review recent theoretical progress in understanding physical processes of composite effects on enhanced third-order nonlinear optical responses of various kinds of the recently-proposed nonlinear optical materials, namely, colloidal nanocrystals with inhomogeneous metallodielectric particles or a graded-index host, metallic films with inhomogeneous microstructures adjusted by ion doping or temperature gradient, composites with compositional gradation or graded particles, and magneto-controlled ferrofluidbased nonlinear optical materials.

We theoretically explore a type of bifunctional cloak possessing both electrical and thermal cloaking functionality. We employ a composite material to design the cloak shell. By using effective medium theory, the effective electrical and thermal conductivities of the composite material should meet the perfect conductivity profile calculated from the coordinate transformation approach. In the design, we choose nonspherical nanoparticles with appropriate electrical and thermal conductivities, shape aspects, and volume fractions. Furthermore, finite element simulations are performed to verify the properties of such bifunctional cloaks.

How to macroscopically control the flow of heat at will is up to now a challenge, which, however, is very important for human life since heat flow is a ubiquitous phenomenon in nature. Inspired by intelligent electronic components or intelligent materials, here we demonstrate, analytically and numerically, a unique class of intelligent bifunctional thermal metamaterials called thermal cloakconcentrators, which can automatically change from a cloak (concentrator) to a concentrator (cloak) when the applied temperature field decreases (increases). For future experimental realization, the behavior is also confirmed by assembling homogeneous isotropic materials according to the effective medium theory. The underlying mechanism originates from the effect of nonlinearity in thermal conduction. This work not only makes it possible to achieve a switchable Seebeck effect, but also offers guidance both for macroscopic manipulation of heat flow at will and for the design of similar intelligent multifunctional metamaterials in