  With this study we analyze the fluctuations of an electronic only heat
current across a molecular wire. The wire is composed of a single energy level
which connects to two leads which are held at different temperatures. By use of
the Green function method we derive the finite frequency power spectral density
(PSD) of the emerging heat current fluctuations. This result assumes a form
quite distinct from the power spectral density of the accompanying electric
current noise. The complex expression simplifies considerably in the limit of
zero frequency, yielding the heat noise intensity. The heat noise intensity
still depends on the frequency in the zero-temperature limit, assuming
different asymptotic behaviors in the low- and high-frequency regimes. These
findings evidence that heat transport across molecular junctions can exhibit a
rich structure beyond the common behavior which emerges in the linear response
limit.
