Heat transference through quantum fluctuations

Experiments show that quantum fluctuations can allow heat to be transported between two objects separated by a vacuum gap. This effect could be harnessed to exploit and control heat transfer in nanoscale devices.

Phonon transmission across a vacuum. Fong et al. show that phonons — vibrations in an atomic lattice — can be transported between objects that are separated by a vacuum gap. To understand how this process occurs, consider an object at a fixed temperature T1. Thermal agitation of the object’s atoms produces phonons that propagate as acoustic waves and cause the object’s surface to exhibit time-varying undulations (the amplitudes of the undulations shown are exaggerated for clarity). A second object, at a fixed temperature T2 < T1, is brought close to the first object, with a vacuum gap between the objects. The undulations of the first object’s surface exert a time-varying ‘Casimir’ force (caused by quantum fluctuations) on the second object’s surface, which gives rise to phonons in the second object. Because phonons are heat carriers, heat is transferred from the first object to the second one.