An international team of scientists from Austria and Germany has launched a new paradigm in magnetism and superconductivity, putting the effects of curvature, topology and 3D geometry in the spotlight of the research of the next decade. | New article in “Advanced Materials”.
Traditionally, the main area, where curvature plays a central role, has been the theory of general relativity. In recent years, however, the impact of curvilinear geometry has entered a variety of disciplines, ranging from solid-state physics and soft-matter physics to chemistry and biology, giving rise to a plethora of emerging fields, such as as curvilinear cell biology, semiconductors, super ﬂ uidity, optics, plasmonics, and van der Waals 2D materials. In modern magnetism, superconductivity and spintronics, the extension of nanostructures into the third dimension has become a major avenue of research due to phenomena induced by geometry, curvature and topology. This approach provides a way to improve conventional functionality and launch new functionality by adapting 3D curvature and shape.
“In recent years, experimental and theoretical work has emerged dealing with curvilinear and three-dimensional superconductivities and (anti-) ferromagnetic nano-architectures. However, these studies come from different scientific communities, hence the lack of knowledge transfer between these areas of condensed matter physics such as magnetism and superconductivity ”, explains Oleksandr Dobrovolskiy, director of the SuperSpin Lab at the University of Vienna. “In our group, we are carrying out projects in these two topical areas and it was the aim of our perspective article to build a ‘bridge’ between the communities of magnetism and superconductivity, drawing attention to them. Conceptual aspects of how extending structures in third dimension and curvilinear geometry can modify existing functionality and help launch new functionality on semiconductor systems. ”
“In magnetic materials, geometrically broken symmetry provides a new toolbox for tailoring the anisotropy induced by curvature and chiral responses,” explains Denys Makarov, head of the “Intelligent Materials and Systems” department at Helmholtz-Zentrum Dresden- Rossendorf. “The ability to tune the magnetic responses by designing the geometry of a magnetic wire or thin film is one of the main advantages of curvilinear magnetism, which has a major impact on physics, materials science and science. technology. At present, under his aegis, the fundamental field of curvilinear magnetism includes curvilinear ferro- and antiferromagnetism, curvilinear magnetism, and curvilinear spintronics.
“The main difference in the impact of curvilinear geometry on superconductors compared to (anti-) ferromagnetics lies in the underlying nature of the order parameter”, explains Oleksandr Dobrovolskiy. “Namely, unlike magnetic materials, for which the energetic functionals contain spatial derivatives of vector fields, the description of superconductors is also based on the analysis of energetic functionals containing spatial derivatives of scalar fields. While in magnetism the order parameter is magnetization (vector), for a superconducting state, the absolute value of the order parameter has a physical meaning of the superconducting band gap (scalar). In the future, the extension of hybrid (anti-) ferromagnetic / superconducting structures in the third dimension will allow the study of the interaction between curvature effects in systems with vector and scalar order parameters. However, this progress relies heavily on the development of experimental and theoretical methods and the improvement of computing capacities.
Challenges for Investigating Curvilinear and 3D Nanomagnets and Superconductors
Generally, curvature and torsion effects are expected when the sizes or characteristics of the system become comparable to the respective length scales. Among the different nanofabrication techniques, the writing of complex shaped 3D nano-architectures by focused particle beams has shown the most significant progress in recent years, making these methods the techniques of choice for fundamental and application-oriented studies. in 3D nanomagnetism and superconductivity. . However, the approach of relevant length scales in the low nm range (exchange length in ferromagnetics and superconducting coherence length in nano-printed superconductors) is still beyond the reach of current experimental capacities. At the same time, sophisticated techniques for characterizing magnetic configurations and their dynamics in complex shaped nanostructures are becoming available, including vector X-ray nanotomography and 3D imaging by soft X-ray laminography. Similar studies on superconductors are more delicate because they require cryogenic conditions, calling for the development of such techniques in the years to come.
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