Observation of a gel of quantum vortices in a superconductor at very low magnetic fields

A gel consists of a network of particles or molecules formed for example using the sol-gel process, by which a solution transforms into a porous solid. Particles or molecules in a gel are mainly organized on a scaffold that makes up a porous system. Quantized vortices in type-II superconductors mostly form spatially homogeneous ordered or amorphous solids.*

In the article “Observation of a gel of quantum vortices in a superconductor at very low magnetic fields” José Benito Llorens, Lior Embon, Alexandre Correa, Jesús David González, Edwin Herrera, Isabel Guillamón, Roberto F. Luccas, Jon Azpeitia, Federico J. Mompeán, Mar García-Hernández, Carmen Munuera, Jazmín Aragón Sánchez, Yanina Fasano, Milorad V. Milošević, Hermann Suderow and Yonathan Anahory present high-resolution imaging of the vortex lattice displaying dense vortex clusters separated by sparse or entirely vortex-free regions in β−Bi2Pd superconductor.*

The authors find that the intervortex distance diverges upon decreasing the magnetic field and that vortex lattice images follow a multifractal behavior. These properties, characteristic of gels, establish the presence of a novel vortex distribution, distinctly different from the well-studied disordered and glassy phases observed in high-temperature and conventional superconductors.*

The observed behavior is caused by a scaffold of one-dimensional structural defects with enhanced stress close to the defects. The vortex gel might often occur in type-II superconductors at low magnetic fields. Such vortex distributions should allow to considerably simplify control over vortex positions and manipulation of quantum vortex states.*

The results presented in the article show that vortices are nearly independent to each other at very low magnetic fields and that their position is locked to the defect structure in the sample. This suggests that vortices in this field range are also highly manipulable, much more than in usual hexagonal or disordered vortex lattices.

The magnetic force microscopy (MFM) measurements described in the article were performed in a commercial Low-Temperature  SPM equipment working in the 300–1.8  K temperature range using NANOSENSORS magnetic AFM probes of the type PPP-MFMR that were magnetized prior to the measurement by applying a magnetic field of 1500 G at 10 K.

figure 8 from “Observation of a gel of quantum vortices in a superconductor at very low magnetic fields” by José Benito Llorens et al.:
Behavior of the hexagonal vortex lattice as a function of temperature measured with MFM. In (a)–(c), the images are taken at 2.75,3.75, and 4.5 K, respectively at 300 G. The color scale represents the observed frequency shift. Scale bar is 1μm. Blue lines are the Delaunay triangulation of vortex positions. Blue and red points in (a) highlight vortices with seven and five nearest neighbors respectively. The dark arrow at the bottom highlights the position of the vertical line discussed in the text.
figure 8 from “Observation of a gel of quantum vortices in a superconductor at very low magnetic fields” by José Benito Llorens et al.:
Behavior of the hexagonal vortex lattice as a function of temperature measured with MFM. In (a)–(c), the images are taken at 2.75,3.75, and 4.5 K, respectively at 300 G. The color scale represents the observed frequency shift. Scale bar is 1μm. Blue lines are the Delaunay triangulation of vortex positions. Blue and red points in (a) highlight vortices with seven and five nearest neighbors respectively. The dark arrow at the bottom highlights the position of the vertical line discussed in the text.

*José Benito Llorens, Lior Embon, Alexandre Correa, Jesús David González, Edwin Herrera, Isabel Guillamón, Roberto F. Luccas, Jon Azpeitia, Federico J. Mompeán, Mar García-Hernández, Carmen Munuera, Jazmín Aragón Sánchez, Yanina Fasano, Milorad V. Milošević, Hermann Suderow, and Yonathan Anahory
Observation of a gel of quantum vortices in a superconductor at very low magnetic fields
Physical Review Research 2, 013329 (2020)
DOI:10.1103/PhysRevResearch.2.013329

Please follow this external link to read the full article: https://journals.aps.org/prresearch/pdf/10.1103/PhysRevResearch.2.013329

Open Access: The article “Observation of a gel of quantum vortices in a superconductor at very low magnetic fields” by José Benito Llorens, Lior Embon, Alexandre Correa, Jesús David González, Edwin Herrera, Isabel Guillamón, Roberto F. Luccas, Jon Azpeitia, Federico J. Mompeán, Mar García-Hernández, Carmen Munuera, Jazmín Aragón Sánchez, Yanina Fasano, Milorad V. Milošević, Hermann Suderow, and Yonathan Anahory is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.