Quantum melting
When ice is warmed, the water molecules forming its structure vibrate more and more vigorously until finally the forces between them are no longer strong enough to hold them together - the ice melts and turns into liquid water. Quantum physics predicts that similar phenomena can be observed if the quantum mechanical fluctuations of the particles in a material can be altered. Such changes of state triggered by purely quantum effects - known as quantum phase transitions - play a role in many astonishing phenomena in solid-state systems, including high-temperature superconductivity. Researchers have now specifically altered the magnetic structure of the material TlCuCl3 by exposing it to a varying external pressure at different temperatures. By performing neutron-scattering measurements, they could observe what happens during a quantum phase transition, and compare the "quantum melting" of the magnetic structure with the classical "thermal melting" phase transition. Whether water is liquid or solid, in the form of ice, depends on which of two energies gains the upper hand. One is the bonding energy of the water molecules, the other the kinetic energy of molecular motion, which becomes increasingly vigorous the higher the temperature.
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