  Landau level gaps are important parameters for understanding electronic
interactions and symmetry-broken processes in bilayer graphene (BLG). Here we
present transport spectroscopy measurements of LL gaps in double-gated
suspended BLG with high mobilities in the quantum Hall regime. By using bias as
a spectroscopic tool, we measure the gap {\Delta} for the quantum Hall (QH)
state at filling factor {\nu}={\pm}4 and -2. The single-particle gap for
{\nu}=4 scales linearly with magnetic field B and is independent of the
out-of-plane electric field E. For the symmetry-broken {\nu}=-2 state, the
measured values of gap are 1.1 meV/T and 0.17 meV/T for singly-gated geometry
and dual-gated geometry at E=0, respectively. The difference between the two
values arises from the E-dependence of the gap, suggesting that the {\nu}=-2
state is layer polarized. Our studies provide the first measurements of the
gaps of the broken symmetry QH states in BLG with well-controlled E, and
establish a robust method that can be implemented for studying similar states
in other layered materials.
