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The Enigmatic Universality of Glass
(UNIGLASS)
Quantum Engineering Applied to Fundamental Physics
Institut Néel/CNRS Grenoble
Much of terrestrial matter is amorphous. This includes technologically important materials such as amorphous pharmaceuticals. But glasses (amorphous solids) are not as well understood as crystals. Paradoxically, even though glasses resemble liquids in that they lack long range order, they are rigid.
The low temperature properties of glass are particularly intriguing. Below 1 kelvin, the thermal and mechanical behavior of glass is very different from that of crystals, and it implies the existence of some type of low energy excitations (LEEs) not present in crystals. It is known that the LEEs are generally not impurities and are intrinsic to the glass since the same characteristic low temperature behavior is observed even in very pure glass specimens. But the true identity of the LEEs is a long standing open question. Furthermore, the mechanical dissipation of glass is remarkably universal near 1 kelvin, varying by only about one order of magnitude around Q-1~3×10-4 despite wide variations in glass composition, impurity concentration and structure.
We are addressing these problems using a variety of techniques at ultra-low temperatures. Such temperatures are achieved using dilution refrigeration in combination with adiabatic nuclear demagnetization. In order to probe individual LEEs, nanomechanical resonators are operated in their quantum ground state at 1 mK.
