Kavli Affiliate: Long Zhang
| First 5 Authors: Peipei Lu, Mengju Yuan, Jing Zhang, Qiang Gao, Shuang Liu
| Summary:
In type-I superconductors, zero electrical resistivity and perfect
diamagnetism define two fundamental criteria for superconducting behavior. In
contrast, type-II superconductors exhibit more complex mixed-state physics,
where magnetic flux penetrates the material above the lower critical field Hc1
in the form of quantized vortices, each carrying a single flux quantum. These
vortices form a two-dimensional lattice which persists up to another
irreversible field (Hirr) and then melts into a dissipative liquid phase. The
vortex lattice is fundamental to the magnetic and electrical properties of
type-II superconductors, a third definitive criterion-beyond resistivity and
magnetization-for identifying this phase has remained elusive. Here, we report
the discovery of a dynamic magnetostrictive effect, wherein the geometry of the
superconductor oscillates only under an applied alternating magnetic field due
to the disturbance of the vortex lattice. This effect is detected by a thin
piezoelectric transducer, which converts the excited geometric deformation into
an in-phase ac voltage. Notably, we find a direct and nearly linear
relationship between the signal amplitude and the vortex density in lattice
across several representative type-II superconductors. In the vortex liquid
phase above Hirr, the signal amplitude rapidly decays to zero near the upper
critical field (Hc2), accompanied by a pronounced out-of-phase component due to
enhanced dissipation. This dynamic magnetostrictive effect not only reveals an
unexplored magnetoelastic property of the vortex lattice but also establishes a
fundamental criterion for identifying the type-II superconductors.
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