1208.6130 (Robert S. Whitney)

Nonlinear thermoelectricity in point-contacts at pitch-off: a
catastrophe aids cooling    [PDF]

Robert S. Whitney

We consider heat-engines and refrigeration circuits based on the nonlinear response of point-contacts at pinch-off, allowing for Hartee-like interaction effects. We show that a refrigerator can cool to much lower temperatures than predicted by the thermoelectric figure of merit ZT (which is based on linear-response arguments). The lowest achievable temperature has a discontinuity at a critical driving current I = I_c, of the type called a catastrophe in mathematics. For I > I_c one can in principle cool to absolute zero, when for I < I_c the lowest temperature is about half the ambient temperature. Chargeless particles (typically phonons and photons) stop cooling at a temperature above absolute zero, and above a certain threshold also modify the discontinuity. More generally, we show that any system with a high figure-of-merit should have its nonlinear response analysed; since its figure-of-merit gives little indication of its potential as a refrigerator or heat-engine.

View original: http://arxiv.org/abs/1208.6130