  We study the mass fluctuations in gapped Dirac materials by treating the
mass-term as both a continuous and discrete random variable. Gapped Dirac
materials were proposed to be used as materials for Dark matter sensors. One
thus would need to estimate the role of disorder and fluctuations on the
interband absorption of dark matter. We find that both continuous and discrete
fluctuations across the sample introduce tails (e.g. Lifshitz tails) in the
density of states and the interband absorption rate. We estimate the strength
of the gap filling and discuss implications of these fluctuations on the
performance as sensors for Dark matter detection. The approach used in this
work provides a basic framework to model the disorder by any arbitrary
mechanism on the interband absorption of Dirac material sensors.
