Credit: Image courtesy of Takeshi Egami, Oak Ridge National Laboratory and the University of Tennessee
Liquid helium shows superfluidity—the ability of a fluid to flow without resistance. Now, observation of atomic dynamics by neutron scattering gave insight into this interesting property. The figure shows the excitation energy (E in milli-electron volts) from interactions of neutrons with the liquid helium at various distances (r in Ångstroms) between helium atoms, for the differences between two temperatures: -271.32 degrees Celsius (where the helium is in a superfluid state) and -270.30 degrees Celsius (where the helium is a normal liquid)). A new peak was discovered at r=2.3 Å and E=0.3 meV (yellow region) that indicates quantum tunneling of atoms in the superfluid state.