An electron in a periodic lattice under a uniform electric field oscillates instead of accelerating — a quantum wave packet bounces within the Brillouin zone with period T_B = h/(eFa).
0.12
1.5
0.020
Bloch period T_B = ℏ/eFa. The Wannier-Stark spectrum shows discrete equally-spaced levels E_n = E_0 + neFa. Observable in semiconductor superlattices and cold atom experiments.