Anomalous suppression of superfluidity for ⁴He in Gelsil glass

We have studied the superfluid behavior of liquid ⁴He confined in three samples of Gelsil glass, whose pore size distribution was examined by measuring N₂ pressure isotherm. It was found that the superfluid transition temperature under the saturation vapor pressure is 1.37 K for one of the samples whose pore size ranges up to around 6 nm, while it is 0.83 K for another one in which the distribution of pore size is small above 4 nm. Both of the samples have a bottleneck structure of the same size. These results demonstrate that the suppression of superfluidity is related to the pore size distribution rather than the size of the neck.