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Low temperature physics, including the physics of highly confined superfluid 3He; disordered superfluids; glass at low temperatures, micro- and nano-mechanical resonators, their design, optimization, non-linear characteristics, and the role of stress on these structures and graphene resonators.
- Cornell Center for Materials Research (CCMR)
- Kavli Institute at Cornell for NanoScale Science
- Laboratory of Atomic and Solid State Physics (LASSP)
Significant effort is devoted to the topological superfluid 3He. Under confinement, the role of surfaces, edges and geometry becomes important and represents the opportunity to explore and utilize properties of this most unusual state of matter. We have constructed (and operated) a series of micromachined cells to probe superfluid 3He in the “2D” limit, where the superfluid is confined between two well characterized silicon/glass surfaces separated by distances on the order of a few coherence lengths. New experiments are planned using a thermal conduction cells, cells where there are many interfaces possible between the competing A and B phases, in others where the nucleation of the B phase from the A phase will be examined thoroughly. Cells involving direct wafer bonding will probe the superfluid under more confinement where novel superfluid phases are expected to emerge. A next generation of cells where transport behavior akin to the Quantum Hall effect, to SNS and NSN junctions are also being planned. Devices that are ready for mounting include a state-of-the-art nano string to be operated in 3He to probe the superfluid gap locally as well as explore interactions with quasiparticles. Other topics under active investigation are non-classical flow properties of confined 3He.
The study of superfluid 3He in aerogel: We use high Q oscillators, and thermal conductivity to look for phase transitions and assay the superfluid fraction of 3He in aerogel in the millikelvin temperature range. We are exploring the A-B transition, effects of magnetic field to probe the nature of the superfluid as well as new anisotropic aerogels to “orient” the superfluid order parameter.
Graphene: A third area of interest is in the mechanical properties of graphene resonators. The mechanical properties of the membrane can provide insight into nonlinearities. We also couple resonators to the optical field and use that coupling to tailor the mechanical properties of the membranes. This work is being carried out in collaboration with the McEuen and Craighead groups.
Abhilash Sebastian, Nik Zhelev
Tunable phonon-cavity coupling in graphene membranes, R. De Alba, F. Massel, I. R. Storch, T. S. Abhilash, A. Hui, P. L. McEuen, H. G. Craighead J. M. Parpia Nature Nanotechnology 11, 741–746 (2016). doi:10.1038/nnano.2016.86 http://www.nature.com/nnano/journal/v11/n9/full/nnano.2016.86.html
Phase Diagram of the Topological Superfluid 3He Confined in a Nanoscale Slab Geometry, Levitin, L.V.; Bennett, R.G.; Casey, A.; Cowan, B.; Saunders, J.; Drung, D.; Schurig, T.; Parpia, J.M. Science, 340, 841-4, (2013).
Observation of a new superfluid phase for 3He embedded in nematically ordered aerogel, N. Zhelev, M. Reichl, T.S. Abhilash, E.N. Smith, K.X. Nguyen, E.J. Mueller J.M. Parpia, Nature Communications, (2016) DOI: 10.1038/ncomms12975