R. T. Azuah

Bose-Einstein condensation in solid 4He.

We present neutron scattering measurements of the atomic momentum distribution n(k) in solid helium under a pressure p=41 bar (molar volume Vm=20.01+/-0.02 cm3/mol) and at temperatures between 80 and 500 mK. The aim is to determine whether there is Bose-Einstein condensation (BEC) below the critical temperature, Tc=200 mK, where a superfluid density has been observed. Assuming BEC appears as a macroscopic occupation of the k=0 state below Tc, we find a condensate fraction of n0=(-0.10+/-1.20)% at T=80 mK and n0=(0.08+/-0.78)% at T=120 mK, consistent with zero. The shape of n(k) also does not change on crossing Tc within measurement precision.

Enhanced Bose?Einstein condensation and kinetic energy of liquid 4He near a free surface

We present neutron scattering measurements of Bose–Einstein condensation (BEC) in liquid 4He adsorbed in thick layers on an MgO substrate to study whether the condensate fraction, n0, is increased near a free surface of liquid 4He. The data show that there is definitely a condensate in the layers adsorbed on the substrate with a condensate fraction comparable to that of bulk liquid 4He. Two methods of analysis are employed to cross-check the results. The data indicate that the condensate fraction increases significantly when the number of adsorbed layers is reduced. This effect is independent of the analysis technique used. In addition, a significant increase in the kinetic energy of the 4He atoms is observed when the number of adsorbed layers is reduced.

The Momentum Distribution of Liquid

We present high-resolution neutron Compton scattering measurements of liquid

^3

^3

He

He below its renormalized Fermi temperature. Theoretical predictions are in excellent agreement with the experimental data when instrumental resolution and final state effects are accounted for. Our results resolve the long-standing inconsistency between theoretical and experimental estimates of the average atomic kinetic energy.

The momentum distribution of liquid 3He

We present high-resolution neutron Compton scattering measurements of liquid

Bose-Einstein Condensate in Solid Helium

^3

Bose-Einstein Condensation in SolidHe4

He below its renormalized Fermi temperature. Theoretical predictions are in excellent agreement with the experimental data when instrumental resolution and final state effects are accounted for. Our results resolve the long-standing inconsistency between theoretical and experimental estimates of the average atomic kinetic energy.

Condensate and final-state effects in superfluid {sup 4}He

We present neutron scattering measurements of the atomic momentum distribution n(k) in solid helium under a pressure p=41 bar (molar volume Vm=20.01+/-0.02 cm3/mol) and at temperatures between 80 and 500 mK. The aim is to determine whether there is Bose-Einstein condensation (BEC) below the critical temperature, Tc=200 mK, where a superfluid density has been observed. Assuming BEC appears as a macroscopic occupation of the k=0 state below Tc, we find a condensate fraction of n0=(-0.10+/-1.20)% at T=80 mK and n0=(0.08+/-0.78)% at T=120 mK, consistent with zero. The shape of n(k) also does not change on crossing Tc within measurement precision.

Quantum momentum distribution and kinetic energy in solid 4He.

We present neutron scattering measurements of the atomic momentum distribution n(k) in solid helium under a pressure p=41 bar (molar volume Vm=20.01+/-0.02 cm3/mol) and at temperatures between 80 and 500 mK. The aim is to determine whether there is Bose-Einstein condensation (BEC) below the critical temperature, Tc=200 mK, where a superfluid density has been observed. Assuming BEC appears as a macroscopic occupation of the k=0 state below Tc, we find a condensate fraction of n0=(-0.10+/-1.20)% at T=80 mK and n0=(0.08+/-0.78)% at T=120 mK, consistent with zero. The shape of n(k) also does not change on crossing Tc within measurement precision.