  We present a novel mode of neutrinoless double beta decay with emission of a
light Majoron-like scalar particle phi. We assume it couples via an effective
seven-dimensional operator with a (V+A) lepton current and (V+-A) quark
currents leading to a long-range contribution that is unsuppressed by the light
neutrino mass. We calculate the total double beta decay rate and determine the
fully differential shape for this mode. We find that future double beta decay
searches are sensitive to scales of the order Lambda_NP ~ 1 TeV for the
effective operator and a light scalar m_phi < 0.2 MeV, based on ordinary double
beta decay Majoron searches. The angular and energy distributions can deviate
considerably from that of two-neutrino double beta decay, which is the main
background. We point out possible ultraviolet completions where such an
effective operator can emerge.
