  The measurement of the energy spectrum of cosmic ray helium nuclei from 70
GeV to 80 TeV using 4.5 years of data recorded by the DArk Matter Particle
Explorer (DAMPE) is reported in this work. A hardening of the spectrum is
observed at an energy of about 1.3 TeV, similar to previous observations. In
addition, a spectral softening at about 34 TeV is revealed for the first time
with large statistics and well controlled systematic uncertainties, with an
overall significance of $4.3\sigma$. The DAMPE spectral measurements of both
cosmic protons and helium nuclei suggest a particle charge dependent softening
energy, although with current uncertainties a dependence on the number of
nucleons cannot be ruled out.
