Helium at elevated pressures: Quantum liquid with non-static shear rigidity

The properties of liquid helium have always been a fascinating subject to scientists. The phonon theory of liquids, taking into account liquid non-static shear rigidity, is employed here for studying internal energy and heat capacity of compressed liquid He-4. We demonstrate the good agreement of calculated and experimental heat capacity of liquid helium at elevated pressures and supercritical temperatures. Unexpectedly, helium remains a quantum liquid at elevated pressures for a wide range of temperature supporting both longitudinal and transverse-like phonon excitations. We have found that in the very wide pressure range of 5 MPa-500MPa, liquid helium near melting temperature is both solid-like and quantum. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795340]