Intertwined superfluid and density wave order in two-dimensional 4He. / Nyeki, Jan; Phillis, Anastasia; Ho, Andrew; Lee, Derek; Coleman, Piers; Parpia, Jeevak; Cowan, Brian; Saunders, John.
In: Nature Physics, Vol. 13, 06.02.2017, p. 455-459.Research output: Contribution to journal › Letter › peer-review
Accepted author manuscript, 12.3 MB, PDF document
Superfluidity is a manifestation of the operation of the laws of quantum mechanics on a macroscopic scale. The conditions under which superfluidity becomes manifest have been extensively explored experimentally in both quantum liquids (liquid 4He being the canonical example) and ultracold atomic gases, including as a function of dimensionality. Of particular interest is the hitherto unresolved question of whether a solid can be superfluid. Here we report the identification of a new state of quantum matter with intertwined superfluid and density wave order in a system of two-dimensional bosons subject to a triangular lattice potential. Using a torsional oscillator we have measured the superfluid response of the second atomic layer of 4He adsorbed on the surface of graphite, over a wide temperature range down to 2 mK. Superfluidity is observed over a narrow range of film densities, emerging suddenly and subsequently collapsing towards a quantum critical point. The unusual temperature dependence of the superfluid density in the limit of zero temperature and the absence of a clear superfluid onset temperature are explained, self-consistently, by an ansatz for the excitation spectrum, reflecting density wave order, and a quasi-condensate wavefunction breaking both gauge and translational symmetry.
Original language | English |
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Pages (from-to) | 455-459 |
Number of pages | 5 |
Journal | Nature Physics |
Volume | 13 |
DOIs | |
Publication status | Published - 6 Feb 2017 |
Research output: Contribution to journal › Special issue › peer-review
Project: Research
ID: 27876486