A collaborative team from MagTop, the Institute of Physics PAS in Warsaw and the URANOS beamline researchers at the SOLARIS Synchrotron, has unveiled an unexpected transformation in the 2D quantum material NbSe2. The article published in Physical Review B, titled ‘Magnetic frustration enforced electronic reconstruction in Ni-intercalated NbSe2: Suppression of electronic orders’ demonstrates that introducing nickel atoms into the crystal, forces electronic reconstruction, eliminating its characteristic such as superconductivity and charge ordering due to magnetic frustration.
Niobium diselenide (NbSe2) is a well-known 2D layered crystal where electrons organize themselves in remarkable ways, it exhibits non-magnetic ground state. Around 30 K, the electrons form a charge-density wave; a periodic ripple in their density and at 7 K, electrons combine into pairs and the material becomes superconducting, carrying electric current without resistance. These two electronic orders coexist naturally and make NbSe2 a model system for studying complex quantum behaviour.
In the article, researchers explored what happens when nickel atoms are inserted between the layers of NbSe2 i.e. Ni0.19NbSe2. This particular, intermediate concentration of Ni, was chosen to introduce moderate disorder into the studied system. Instead of simply disturbing the structure, the added nickel fundamentally changes how electrons move and interact. Both superconductivity and the charge-density wave disappear, and the material begins to behave like a frustrated magnet. Measurements show that the intercalated nickel atoms introduce magnetic moments that interact with each other in conflicting ways. As the sample is cooled, these moments attempt to align in opposite directions, but cannot settle into a single, well-ordered pattern. This “magnetic frustration” is a hallmark of systems where competing interactions prevent the formation of a simple magnetic state.
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Image: Fermi surface maps at 84 K of pristine NbSe2 and Niinterncalated NbSe2 measured using ARPES. (a), (b) Comparison of the Fermi surfaces for pristine NbSe2 and Ni0.19NbSe2 resp. obtained from the sum of intensities of horizontal and vertical linear polarizations. The Ni-intercalated sample shows clear Fermi surface reconstruction, indicated by red arrows. (c), (d) Fermi surface maps of NbSe2 and Ni0.19NbSe2 obtained from the sum of intensities of left- and right-circular polarizations, further highlighting modifications in the electronic structure due to Ni intercalation (red arrows).