  We propose a mechanism of active near-field heat transfer modulation relying
on externally tunable metamaterials. A large modulation effect is observed and
can be explained by the coupling of surface modes, which is dramatically varied
in the presence of controllable magnetoelectric coupling in metamaterials. We
finally discuss how a practical picosecond-scale thermal modulator can be made.
This modulator allows manipulating nanoscale heat flux in an ultrafast and
noncontact (by optical means) manner.
