Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this Letter, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum critical point is manifested as a stable Gaussian fixed point with a large basin of attraction. Implications of our findings to the superconductivity of the iron pnictides are also discussed.
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http://dx.doi.org/10.1103/PhysRevLett.121.057001 | DOI Listing |
ACS Mater Au
January 2025
Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States.
Lanthanide materials with a 4f electron configuration (S) offer an exciting system for realizing multiple addressable spin states for qubit design. While the S ground state of 4f free ions displays an isotropic character, breaking degeneracy of this ground state and excited states can be achieved through local symmetry of the lanthanide and the choice of ligands. This makes Eu attractive as it mirrors Gd in exhibiting the S ground state, capable of seven spin-allowed transitions.
View Article and Find Full Text PDFNano Lett
January 2025
National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
Altermagnetism, as a recently discovered unconventional antiferromagnetism, allows the lifting of spin degeneracy without net magnetization. The spin splitting of the intrinsic altermagnets is protected by the spin space group symmetry and is therefore difficult to control externally. Here, we propose an extrinsic altermagnet as a complement to the intrinsic altermagnet, whose spin splitting is induced by and can be significantly modulated by the electric field.
View Article and Find Full Text PDFStructure
December 2024
Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address:
Brain Connect
December 2024
Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA.
The concept of community structure, based on modularity, is widely used to address many systems-level queries. However, its algorithm, based on the maximization of the modularity index Q, suffers from degeneracy problem, which yields a set of different possible solutions. In this work, we explored the degeneracy effect of modularity principle on resting-state functional magnetic resonance imaging (rsfMRI) data, when it is used to parcellate the cingulate cortex using data from the Human Connectome Project.
View Article and Find Full Text PDFProg Nucl Magn Reson Spectrosc
December 2024
Center for Cooperative Research in Biosciences (CIC bioGUNE), Basque Research and Technology Alliance (BRTA), 48160 Derio, Bizkaia, Spain; Ikerbasque, Basque Foundation for Science, Plaza Euskadi 5, 48009 Bilbao, Spain; Department of Organic & Inorganic Chemistry, Faculty of Science and Technology, University of the Basque Country, EHU-UPV, 48940 Leioa, Bizkaia, Spain; Centro de Investigacion Biomedica En Red de Enfermedades Respiratorias, 28029 Madrid, Spain. Electronic address:
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