Rapid Response to Supersolidity: ‘Is It There or Is It Not?’ May Be the Answer as Well as the Question

with changes in a macroscopic collection of molecules he had witnessed—water which changes from solid to liquid to vapor as temperature increases. Fast forward almost exactly fi ve hundred years since “Hamlet” was fi rst performed at the Globe to the year 2004 and the Penn State University laboratory of physicist Moses Chan, where temperatures can be lowered to 0.2 Kelvin (0.2 above absolute zero) and pressures on a quantum crystal of helium4 can be increased to 25 times that of earth’s atmosphere at sea level. What may be emerging is a new phase of matter—a “supersolid” both crystalline and superfl uid. At issue is the nature of “solid.” Said Chan, “We thought a crystalline solid is something we all understand—rigid, reliable, stay-put. Our data is indicating, ‘no, not quite’ if the temperature is low enough.”