PIRSA:13100065

From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

Beamish, J. (2013). From Supersolidity to Giant Plasticity: Defects in Quantum Crystals. Perimeter Institute. https://pirsa.org/13100065

Beamish, John. From Supersolidity to Giant Plasticity: Defects in Quantum Crystals. Perimeter Institute, Oct. 09, 2013, https://pirsa.org/13100065 

          @misc{ pirsa_PIRSA:13100065,
            doi = {10.48660/13100065},
            url = {https://pirsa.org/13100065},
            author = {Beamish, John},
            keywords = {Condensed Matter},
            language = {en},
            title = {From Supersolidity to Giant Plasticity: Defects in Quantum Crystals},
            publisher = {Perimeter Institute},
            year = {2013},
            month = {oct},
            note = {PIRSA:13100065 see, \url{https://pirsa.org}}
          }

John Beamish University of Alberta

DOI 10.48660/13100065
Collection
Talk Type Scientific Series
Subject

Abstract

In 2004, Kim and Chan reported torsional oscillator experiments on 4He crystals which showed evidence of “non-classical rotational inertia”, the mass decoupling expected for a long-sought “supersolid” state. It soon became clear that this behavior is not a property of perfect crystals – defects are involved. In 2007, we made elastic measurements which showed, to our surprise, that the shear modulus of solid 4He increases dramatically below 0.2 K, with the same dependence on temperature, amplitude and 3He impurity concentration as the torsional oscillator anomaly. These shear modulus changes are due to dislocations and their interactions with impurities and vacancies. Our experiments raised an obvious question – could the torsional oscillator behavior be an artifact of the elastic changes, rather than evidence of supersolidity? During the past two years it has become clear that the answer is “yes” and interest has focused on the properties of dislocations in a quantum solid like 4He. By growing high quality single crystals in optical cells, we have now been able to explore the behavior of dislocations in 4He in unprecedented detail. In some crystals the dislocations reduce the shear modulus by more than 80%, an extraordinary effect we describe as “giant plasticity”. Solid helium has proved to be an ideal system in which to do materials science, as well as to address fundamental questions about quantum solids.