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Data for Reexamination of the electronic phase diagram of doped NiS2: Electronic, magnetic, and structural inhomogeneity across the Mott insulator-metal transition
(2024-11-04) Tao, Yu; Das, Bhaskar; Calder, Stuart; Day-Roberts, Ezra; Maiti, Moumita; Lee, Yeon; Komar, Caitlyn; Birol, Turan; Leighton, Chris; leighton@umn.edu; Leighton, Chris; Leighton Electronic and Magnetic Materials Lab; Chemical Engineering and Materials Science, University of Minnesota
Pyrite-structure NiS2 is, in principle, a model antiferromagnetic Mott insulator that can be electron doped, hole doped, and bandwidth controlled. Despite decades of study, however, the electronic and magnetic behavior of NiS2 have proven challenging to understand. Here, we build on recent advances establishing surface conduction in NiS2 to completely reexamine the electronic phase behavior of electron- and hole-doped single-crystal Ni1-xCuxS2 and Ni1-xCoxS2. Magnetometry, heat capacity, neutron diffraction, and electronic transport measurements suggest that prior work missed vital details of the magnetic ordering in this system. While electron and hole doping rapidly increase the antiferromagnetic ordering temperature (by as much as 4-fold by x  0.1), signatures remain of antiferromagnetic and weak ferromagnetic ordering at the same temperatures as in undoped NiS2. As these undoped ordering temperatures remain constant, the associated magnetic moments are diminished by doping, strongly implicating electronic/ magnetic phase coexistence across the Mott insulator-metal transition. Substantial structural changes and inhomogeneity accompany these evolutions, highlighting the importance of structural-chemical-electronic-magnetic coupling in NiS2. The insulator-metal transition is also strongly electron/hole asymmetric, which we interpret with the aid of complementary dynamical mean-field theory results. These findings significantly revise and advance our understanding of the electronic phase behavior of this prototypical Mott insulator, highlighting the essential role of electronic, magnetic, structural, and chemical inhomogeneity across the Mott transition. This dataset contains all digital data in the published paper of the same name.
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Supporting Data for Circular Dichroism of Distorted Double Gyroid Thin Film Metamaterials
(2024-11-04) McGuinness, Emily; Magruder, Benjamin; Dorfman, Kevin; Ellison, Chris; Ferry, Vivian; veferry@umn.edu; Ferry, Vivian; Department of Chemical Engineering and Materials Science, University of Minnesota
Strong circular dichroism (CD) has been reported in triply periodic, co-continuous gyroid thin films for certain orientations and surface terminations. However, processing of gyroid thin films introduces distortions experimentally, creating a mismatch between the structures created practically and those explored computationally. This work explores the impact of compression normal to the substrate (z-compression) with conserved volume in (110)-oriented plasmonic silver double gyroid thin films on CD using finite-difference time-domain (FDTD) simulations. As compression reaches fifteen percent and above, new features emerge including termination-dependent opposite-handed CD responses and, at larger compressions, shorter wavelength responses that span many surface terminations. The longest wavelength responses of the system red-shift with increasing compression. The top surface structure contributes strongly to the emerging opposite-handed features and red-shifting of wavelengths. However, the less surface termination dependent features arise from a mixture of contributions from the top surface and interior of the films. Interplay of these leads to CD-switching phenomena as a function of compression for certain terminations and wavelengths. When alternative methods are utilized to compress the system, such as compression with a Poisson’s ratio of 0.33 (comparable to polystyrene) or the generation of compressed equilibrium structures with non-affine strut changes via self-consistent field theory, similar optical responses persist. Overall, this study highlights the significant impact experimentally relevant distortions (especially compression and some non-affine structural shifts) can have on the CD response of block copolymer templated plasmonic double gyroid thin films, and provides mechanistic insight into the film interior versus surface contributions to the CD response during compression.
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Senior Research and Extension Coordinator
(2024-10-14) Bilotta, John
Minnesota Urban Stormwater Research Needs and Priorities - 2024 & 2025
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Annual Northeast Regional Science Fair Newsletter (1979-02)
(1979-02) University of Minnesota, Duluth. College of Letters and Science