Detailed guidelines on how to unlock T11 troops can be found here, how to unlock T12 here and T13 here.
T11 and T12 troops are slightly different from other troops. They both require additional resources to train them – latent energy.
T11 requires 1 can of latent energy per troop.
T12 requires 2 cans of latent energy per troop.
T13 requires 3 cans of latent energy per troop.