Shifting Erasure Cost below the Landauer Bound with a Demon-Biased Thermal Bath

The Landauer principle establishes a fundamental lower bound on the energetic cost of the erasure for a one-bit memory in thermal equilibrium. Here, we experimentally demonstrate how this bound can be shifted by introducing a hysteretic bias h in the feedback-generated virtual potential of a microresonator acting as the information bit. By tuning the hysteresis, we engineer a nonequilibrium steady state with an adjustable effective temperature different from the bath temperature T_{0}, enabling erasure processes that consume over 20% below the Landauer bound k_{B}T_{0}ln2. Unlike sub-Landauer protocols that rely on a deliberately prepared nonequilibrium initial state, the cost reduction observed here is generated during reset by an embedded feedback bias acting as an information engine. The same platform reproduces the standard quasistatic result at h=0 and shifts the asymptotic erasure cost above or below it for h≠0. Our results provide a clean experimental playground for theoretical descriptions based on feedback, information flow, hidden controller states, and generalized nonequilibrium Landauer relations.