  We investigate theoretically charge-noise induced spin dephasing of a hole
confined in a quasi-two-dimensional silicon quantum dot. Central to our
treatment is accounting for higher-order corrections to the Luttinger
Hamiltonian. Using experimentally reported parameters, we find that the new
terms give rise to sweet-spots for the hole-spin dephasing, which are sensitive
to device details: dot size and asymmetry, growth direction, and applied
magnetic and electric fields. Furthermore, we estimate that the dephasing time
at the sweet-spots is boosted by several orders of magnitude, up to order of
milliseconds.
