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Phase Diagram of the Topological Superfluid 3He Confined in a Nanoscale Slab Geometry

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Science  17 May 2013:
Vol. 340, Issue 6134, pp. 841-844
DOI: 10.1126/science.1233621

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Confined Helium

Helium-3 (3He) has superfluid phases closely related to topological insulators and topological superconductors. In geometrical confinement, 3He is expected to support exotic excitations, but its phase diagram is largely unknown, as such measurements are experimentally challenging. Levitin et al. (p. 841) confine 3He in a slab geometry of defined height and use nuclear magnetic resonance as a probe. As predicted by theory, the authors find that the confinement stabilizes some of the superfluid phases across a larger portion of the phase diagram with respect to the bulk and potentially provides a testbed for topological superfluidity.

Abstract

The superfluid phases of helium-3 (3He) are predicted to be strongly influenced by mesoscopic confinement. However, mapping out the phase diagram in a confined geometry has been experimentally challenging. We confined a sample of 3He within a nanofluidic cavity of precisely defined geometry, cooled it, and fingerprinted the order parameter using a sensitive nuclear magnetic resonance spectrometer. The measured suppression of the p-wave order parameter arising from surface scattering was consistent with the predictions of quasi-classical theory. Controlled confinement of nanofluidic samples provides a new laboratory for the study of topological superfluids and their surface- and edge-bound excitations.

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