Measurement of the superfluid fraction of a supersolid by Josephson effect
A new class of superfluids and superconductors with spatially periodic modulation of the superfluid density is arising 1 – 12 . It might be related to the supersolid phase of matter, in which the spontaneous breaking of gauge and translational symmetries leads to a spatially modulated macroscopic wa...
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| Published in: | Nature (London) Vol. 629; no. 8013; pp. 773 - 777 |
|---|---|
| Main Authors: | , , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
London
Nature Publishing Group UK
23-05-2024
Nature Publishing Group |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | A new class of superfluids and superconductors with spatially periodic modulation of the superfluid density is arising
1
–
12
. It might be related to the supersolid phase of matter, in which the spontaneous breaking of gauge and translational symmetries leads to a spatially modulated macroscopic wavefunction
13
–
16
. This relation was recognized only in some cases
1
,
2
,
5
–
9
and there is the need for a universal property quantifying the differences between supersolids and ordinary matter, such as the superfluid fraction, which measures the reduction in superfluid stiffness resulting from the spatial modulation
16
–
18
. The superfluid fraction was introduced long ago
16
, but it has not yet been assessed experimentally. Here we demonstrate an innovative method to measure the superfluid fraction based on the Josephson effect, a ubiquitous phenomenon associated with the presence of a physical barrier between two superfluids or superconductors
19
, which might also be expected for supersolids
20
, owing to the spatial modulation. We demonstrate that individual cells of a supersolid can sustain Josephson oscillations and we show that, from the current–phase dynamics, we can derive directly the superfluid fraction. Our study of a cold-atom dipolar supersolid
7
reveals a relatively large sub-unity superfluid fraction that makes realistic the study of previously unknown phenomena such as partially quantized vortices and supercurrents
16
–
18
. Our results open a new direction of research that may unify the description of all supersolid-like systems.
A new method based on the Josephson effect is described, allowing to measure the superfluid fraction of a supersolid, which captures the effect of spatially periodic modulation leading to reduction in the stiffness of superfluids. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0028-0836 1476-4687 |
| DOI: | 10.1038/s41586-024-07361-9 |