2021/12/16 by Haley M. Cole, M. B. Venuti, Cole, Haley M. +9
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #FOS: Physical sciences #Geomagnetism and Paleomagnetism Studies #Physics of Superconductivity and Magnetism #Superconductivity (cond-mat.supr-con) #Superconductivity in MgB2 and Alloys
paper · pdf · doi:10.48550/arxiv.2112.08667
openalex publication_date 2021/12/16 · openalex created_date 2022/05/05 · openalex updated_date 2026/07/28
In type-II superconductors exposed to magnetic fields between upper and lower critical values, Hc1 and Hc2, penetrating magnetic flux forms a lattice of vortices whose motion can induce dissipation. Consequently, the magnetization M of superconductors is typically progressively weakened with increasing magnetic field B ∝ nv (for vortex density nv). However, some materials exhibit a non-monotonic M(B), presenting a maximum in M at what is known as the second magnetization peak. This phenomenon appears in most classes of superconductors, including low Tc materials, iron-based, and cuprates, complicating pinpointing its origin and garnering intense interest. Here, we report on vortex dynamics in optimally doped and overdoped HgBa2CuO4+x crystals, with a focus on a regime in which plastic deformations of the vortex lattice govern magnetic properties. Specifically, we find that both crystals exhibit conspicuous second magnetization peaks and, from measurements of the field- and temperature- dependent vortex creep rates, identify and characterize phase boundaries between elastic and plastic vortex dynamics, as well as multiple previously unreported transitions within the plastic flow regime. We find that the second magnetization peak coincides with the elastic-to-plastic crossover for a very small range of high fields, and a sharp crossover within the plastic flow regime for a wider range of lower fields. We find evidence that this transition in the plastic flow regime is due to a dimensional crossover, specifically a transition from 3D to 2D plastic dynamics.