This is a condition for a typical liquidity trap; hence my proposal for applying a negative return, a charge, on such deposits.

I agree with Greg Mankiw[1] that it is time for central banks to stop pretending that zero is the floor for nominal interest rates.  There is no theoretical or practical reason for not having the Federal Funds target rate and market rates at, say, minus five percent, if that is what your Taylor rule, or whatever heuristic guides your official policy rate, suggests.