  Bilayer MoS2 is a centrosymmetric semiconductor with degenerate spin states
in the six valleys at the corners of the Brillouin zone. It has been proposed
that breaking of this inversion symmetry by an out-of-plane electric field
breaks this degeneracy, allowing for spin and valley lifetimes to be
manipulated electrically in bilayer MoS2 with an electric field. In this work,
we report phase-coherent transport properties of double-gated mono-, bi-, and
tri-layer MoS2. We observe a similar crossover from weak localization to weak
anti-localization, from which we extract the spin relaxation time as a function
of both electric field and temperature. We find that the spin relaxation time
is inversely proportional to momentum relaxation time, indicating that
D'yakonov-Perel mechanism is dominant in all devices despite its
centrosymmetry. Further, we found no evidence of electric-field induced changes
in spin-orbit coupling strength. This suggests that the interlayer coupling is
sufficiently weak and that electron-doped dichalcogenide multilayers behave
electrically as decoupled monolayers.
