
#1
Feb2214, 06:48 AM

P: 1

Hello,
If we first consider Helium4 we can calculate the critical velocity via [itex]\frac{d\epsilon(p)}{dp}=\frac{\epsilon(p)}{p}[/itex] where [itex]\epsilon(p)=\frac{(pp_0)^2}{2\mu}+\Delta[/itex] is the dispersion relation for roton excitations in Helium4. Putting in the constants [itex]\mu=0.164 m_4[/itex] is the effective mass, [itex]\Delta/k_B=8.64[/itex]K, [itex]p_0/\hbar=19.1[/itex]nm you get roughly [itex]v_c=59.3[/itex]m/s. Now I want to do the same calculation for Helium3 but can't find the values of the constants for Helium3, if rotons even exists for Helium3? What is the dispersion relation for Helium3? Taking inspiration from superconductivity and the BCStheory I'm thinking that there will be an energy gap here as well, i.e. no phonon region as for Helium4, but it's hard to find information about this. Can anyone point me in the correct direction? I'm mostly interested in drawing some conclusions about the critical velocity of Helium3 from the calculation above, if it is even possible... Regards, Andreas 


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