Solidification of 4He confined in a nanometer-size channel

Solidification of 4He confined in a one-dimensional 2.8-nm channel of FSM was studied by pressure and heat capacity measurements. It was found that the freezing pressure in the channel is greatly elevated and is between 3.3 and 3.8 MPa at absolute zero. Furthermore, the density change at the liquid-solid transition is evaluated. The decrease in the molar volume is less than 1×10−2 cm3/mol at the transition of 4 MPa, which is about two orders of magnitude smaller than that of bulk. From this observation, we can conclude that solid 4He confined in the channel has a density as low as liquid