Quantum Phase Transition of 4 He Confined in Nano - Porous Media
Keiya Shirahama
Department of Physics, Keio University, Yokohama 223-8522, Japan
Bosons under periodic or random potential have been of great interest. A number of theoretical studies
have predicted various exotic phases, such as Mott insulator, Bose glass and supersolid. 4 He in nano porous media provides us with an exciting opportunity to study strongly correlated Bose liquid and solid
under confinement potential. The quantum properties of 4 He can change drastically by confinement in
porous media. We have studied superfluidity and liquid - solid phase transition of 4 He confined in a porous
glass which has nanopores of 2.5 nm in diameter [1]. The revealed pressure - temperature phase diagram is
quite unprecedented: The superfluid transition temperature approaches 0 K at 3.4 MPa, and the freezing
pressure shifts up about 1 MPa from the bulk one. The features indicate that the confined 4 He undergoes
a superfluid - nonsuperfluid - solid quantum phase transition at 0 K. The nonsuperfluid phase may be
a localized Bose - condensed state, in which global phase coherence is destroyed by strong correlation
between 4 He atoms or by random potential (i.e. the Bose glass). Ultrasound and heat capacity studies,
and a comparison experiment employing a crystalline nano - porous material (3D regular porous structure)
are underway to elucidate the effects of correlation and disorder on the quantum phase transition.
This work is done in collaboration with K. Yamamoto, Y. Shibayama (Keio Univ.), T. Kobayashi and
M. Suzuki (Univ. Electro - Communications).
[1] K. Yamamoto, H. Nakashima, Y. Shibayama, K. Shirahama, Phys. Rev. Lett. 93, 075302 (2004).
Sorting category: Ac Quantum gases, fluids and solids
Keywords: superfluidity, rubidium, cuprate
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