How can we get negative **real** interest rate?
There is a market for inflation-linked bonds. The quoted yield on the bonds is the equivalent of a real yield, with the inflation rate corresponding to expected inflation.

The real yields On US inflation-linked bonds are currently negative. Link to FRED data.

There is no mystery to this.


Nominal yields are effectively pinned to the expected path of the nominal policy rate.
Inflation rates follow developments in the economy.
There is no law of nature that says that the nominal yield has to be above the rate of inflation.