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Thermal self-oscillations in radiative heat exchange

We report the effect of relaxation-type self-induced temperature oscillations in the system of two parallel plates of SiO$_2$ and VO$_2$ which exchange heat by thermal radiation in vacuum. The non-linear feedback in the self-oscillating system is provided by metal-insulator transition in VO$_2$. Using the method of fluctuational electrodynamics we show that under the action of an external laser of a constant power, the temperature of VO$_2$ plate oscillates around its phase transition value. The period and amplitude of oscillations depend on the geometry of the structure. We found that at 500\,nm vacuum gap separating bulk SiO$_2$ plate and 50 nm thick VO$_2$ plate, the period of self-oscillations is 2 s and the amplitude is 4 K which is determined by phase switching at threshold temperatures of phase transition.