Localization of Bose‐Einstein Condensate and Disappearance of Superfluidity of Strongly Correlated Bose Fluid in a Confined Potential

We develop a model for a Bose fluid in a confined potential to study a new quantum phase caused by the localization of the Bose‐Einstein condensate and the disappearance of superfluidity which was recently observed in liquid ⁴He in porous glass at high pressures. The critical pressure for the transition to this phase can be defined by our new analytical criterion, which assumes that the size of the localized Bose‐Einstein condensate is comparable to the scale of confinement. The critical pressure is quantitatively consistent with observations without free parameters.