Hydrogen tunneling modes in $\alpha$-Mn suppressed by elastic stresses

Behavior of the tunneling mode of hydrogen in MnH$_{0.04}$ and MnH$_{0.07}$ under high pressures in sapphire anvils was studied by the method of incoherent inelastic neutron scattering (INS). It is established that the INS peak corresponding to the hydrogen tunneling in a double-well potential disappears at a pressure of 0.8 GPa in a quasi-hydrostatic regime, while being retained without visible changes under pure hydrostatic conditions. An analogous, albeit weaker, suppression of the tunneling mode takes place upon grinding of a freshly prepared sample. The effect of suppression of the hydrogen tunneling modes by applied inhomogeneous elastic stresses is explained by a shift of the energy levels in the adjacent wells caused by the static displacements.