Tunneling splitting of Jahn-Teller ions in oxides.

The magnitude of tunneling splitting, 3Gamma, that governs decoherence in quantum systems under symmetric potentials, is frequently unknown. Using first-principles calculations, we have obtained 3Gamma for a number of E[symbol:see text]e Jahn-Teller impurities in solids. Calculated values span 6 orders of magnitude on passing from KCl:Ag{2+} to MgO:Cu{2+}. Values associated with Cu2+- and Ag2+-doped MgO are 2 orders of magnitude larger than those previously assumed and consistent with the existence of a dynamic Jahn-Teller effect. The origin and enhancement with pressure of these high 3Gamma values is discussed in detail.