Bistable circuts based on non-linear effects (like breakdown)?
Here is a little "philosophy" about this clever "trick"...

Such elements possess negative differential resistance. They are two types - S-shaped (e.g., a neon bulb) and N-shaped (e.g., a tunnel diode). To make them operate in a bistable mode, you have to drive an S-shaped NDR with a low resistive voltage source (having an almost vertical IV curve)...



... and to drive an N-shaped NDR with a high resistive current source (having an almost horizontal IV curve):



Under these conditions, negative differential resistors jump between their two states, and can serve as Schmitt triggers and latches.