I confess that I am a profound skeptic about deep negative nominal interest rates. A slightly higher inflation target and policies to fight the asset price configuration called "secular stagnation" would largely obviate the need, and leave behind a problem easily and straightforwardly dealt with via expansionary fiscal policy. And we really do not know how such an institutional reconfiguration would actually work. Confronted with a choice between known and understood policies that would work, and new ones with unknown side effects and effects that might, I do not undertstand the enthusiasm for the second:

Ruchir Agarwal and Miles Kimball: Enabling Deep Negative Rates to Fight Recessions: A Guide: "we (i) survey approaches to enable deep negative rates... (ii) establish... enabling negative rates while remaining at a minimum distance from the current paper currency policy and minimizing the political costs; (iii) discuss why standard transmission mechanisms... are likely to remain unchanged in deep negative rate territory; and (iv) present communication tools that central banks can use...