Glyde HR, Plantevin O, Fak B, Coddens G, Danielson PS, Schober H
Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA.
Phys Rev Lett. 2000 Mar 20;84(12):2646-9. doi: 10.1103/PhysRevLett.84.2646.
Using inelastic neutron scattering, we have observed well-defined phonon-roton ( p-r) excitations in superfluid 4He in Vycor over a wide wave-vector range, 0.3</=Q</=2.15 A(-1). The p-r energies and lifetimes at all temperatures are the same as in bulk liquid 4He. However, the weight of the single p-r component does not scale with the superfluid fraction rho(S)(T)/rho as it does in the bulk. In particular, we observe a p-r excitation above T(c) = 1.952 K, where rho(s)(T) = 0 in Vycor. This suggests, if the p-r excitation intensity scales with the Bose condensate, that there is a separation of the Bose-Einstein condensation temperature and the superfluid transition temperature T(c) of 4He in Vycor.
利用非弹性中子散射，我们在0.3≤Q≤2.15 Å⁻¹的宽波矢范围内，观测到了超流⁴He在Vycor中定义明确的声子-旋子（p-r）激发。所有温度下的p-r能量和寿命与体相液态⁴He中的相同。然而，单个p-r分量的权重不像在体相中那样随超流分数ρₛ(T)/ρ缩放。特别是，我们在Tₑ = 1.952 K以上观测到一个p-r激发，此时Vycor中的ρₛ(T) = 0。这表明，如果p-r激发强度随玻色凝聚缩放，那么在Vycor中⁴He的玻色-爱因斯坦凝聚温度和超流转变温度Tₑ存在分离。
