Effect of point defects on the performances of Li2MoO4 and Li2WO4 crystals as scintillating cryogenic calorimeters

The use of large scintillating crystals as cryogenic calorimeters was proven to be a promising strategy in the search for the neutrinoless Double Beta Decay (0νββ). Such a rare nuclear process would provide crucial information on the nature of the neutrino (i.e. whether it is a Majorana or a Dirac particle) and on the value of its mass. In this work, scintillating crystals of Li2MoO4, Li2MoO4:Ag, and Li2WO4 grown by the Czochralski technique were studied as they are both promising candidates for scintillating cryogenic calorimeters: the former due to 100Mo isotope suitable for 0νββ search, and the latter because of the presence of 6Li for spin dependent dark matter search. Using various spectroscopic techniques, we investigated the scintillating properties of all these crystals and the effect of point defects on their scintillation performances, evaluating the parameters of the traps involved in the scintillation mechanism and demonstrating for the first time that the temperature dependence of the bright burn phenomenon is tightly correlated with the presence of defects responsible for low temperature thermally stimulated luminescence peaks.