Vortex phases and glassy dynamics in the highly anisotropic superconductor HgBa2CuO4+δ

Serena Eley; Roland Willa; Mun K Chan; Eric D Bauer; Leonardo Civale

doi:10.1038/s41598-020-65224-5

Vortex phases and glassy dynamics in the highly anisotropic superconductor HgBa₂CuO_4+δ

Sci Rep. 2020 Jun 24;10(1):10239. doi: 10.1038/s41598-020-65224-5.

Authors

Serena Eley^{1

2}, Roland Willa^{3

4}, Mun K Chan⁵, Eric D Bauer⁶, Leonardo Civale⁶

Affiliations

¹ Department of Physics, Colorado School of Mines, Golden, CO, 80401, USA. serenaeley@mines.edu.
² Los Alamos National Laboratory, Los Alamos, NM, 87545, USA. serenaeley@mines.edu.
³ Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
⁴ Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany.
⁵ Pulsed Field Facility, National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
⁶ Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.

Abstract

We present an extensive study of vortex dynamics in a high-quality single crystal of HgBa₂CuO_4+δ, a highly anisotropic superconductor that is a model system for studying the effects of anisotropy. From magnetization M measurements over a wide range of temperatures T and fields H, we construct a detailed vortex phase diagram. We find that the temperature-dependent vortex penetration field H_p(T), second magnetization peak H_smp(T), and irreversibility field H_irr(T) all decay exponentially at low temperatures and exhibit an abrupt change in behavior at high temperatures T/T_c >~ 0.5. By measuring the rates of thermally activated vortex motion (creep) S(T, H) = |dlnM(T, H)/dlnt|, we reveal glassy behavior involving collective creep of bundles of 2D pancake vortices as well as temperature- and time-tuned crossovers from elastic (collective) dynamics to plastic flow. Based on the creep results, we show that the second magnetization peak coincides with the elastic-to-plastic crossover at low T, yet the mechanism changes at higher temperatures.