Search for neutrino-less double beta decay with thermal detectors

Neutrino-less double-beta decay (0νββ) is a hypothetical nuclear transition which violates lepton-number conservation and is therefore forbidden by the Standard Model of particle physics. Its observation would unambiguously demonstrate that neutrinos are Majorana particles and would provide unique information about the ordering and absolute scale of neutrino masses. This would have fundamental implications for neutrino physics and cosmology, opening a number of opportunities for many extended models and providing clues to some unanswered questions. The search for this decay is puzzling experimental physicists since about eighty years. After the introduction of the calorimetric approach in the 60s, another real breakthrough was represented by the proposal to use thermal (or low temperature) detectors, which dissolved any limitation in the choice of the detector materials. In this review, we summarize the status of 0νββ searches with thermal detectors and review the most recent results. We provide also some future perspectives in the framework of the international competition.