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1. Bosonic topological insulator intermediate state in the superconductor-insulator transition

   https://doi.org/10.1016/j.physleta.2020.126570  

   Diamantini, M.C.; Mironov, A.Yu.; Postolova, S.M.; Liu, X.; Hao, Z.; Silevitch, D.M.; Kopelevich, Ya.; Kim, P.; Trugenberger, C.A.; Vinokur, V.M. (August 2020, Physics Letters A)
2. The disordered and correlated insulator Bi2CrAl3O9

   https://doi.org/https://doi-org.ezproxy.library.ubc.ca/10.1103/PhysRevB.100.104425  

   Umana, J. C.; Baccarella, A. M.; Steinke, L; Geritano, A; Janssen, Y.; Aronson, M. C; Simonson, J. W. (September 2019, PRB)

   The 3d transition metal insulator Bi2CrAl3O9 forms with a quasi-one-dimensional structure characterized by linear chains of edge-sharing, Cr-and Al-centered, distorted octahedra. The UV/Vis spectrum of high-quality single crystals is marked by broad absorption edges corresponding to direct transitions across a 1.36-eV insulating gap. Measurements of dc magnetic susceptibility χ reveal a fluctuating moment of 2.60±0.01μB/Cr—reduced from the 3.87μB/Cr expected for Cr3+, while the Weiss temperature ΘW=−21±1 K implies that the prevailing local moment interactions are weakly antiferromagnetic in nature. Some 10% of the fluctuating moment is quenched, presumably due to the onset of an antiferromagnetic or spin glass phase at temperature T★=98±3 K, while measurements of magnetization versus field H at T≤10 K scale as H/T0.68(4), suggesting the presence of quantum fluctuations associated with a disordered phase. Density functional theory calculations carried out within the generalized gradient approximation are in excellent agreement with experimental results, asserting that short-range magnetic interactions remnant above T★ stabilize the insulating state 

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3. The Microelectrode Insulator Influences Water Nanodroplet Collisions

   https://doi.org/10.1021/acs.analchem.3c00287  

   Vannoy, Kathryn J.; Renault, Christophe; Dick, Jeffrey E. (January 2023, Analytical Chemistry)
4. Non-equilibrium states and interactions in the topological insulator and topological crystalline insulator phases of NaCd4As3

   https://doi.org/10.1063/4.0000273  

   Kafle, Tika R; Zhang, Yingchao; Wang, Yi-yan; Shi, Xun; Li, Na; Sapkota, Richa; Thurston, Jeremy; You, Wenjing; Gao, Shunye; Dong, Qingxin; et al (January 2025, Structural Dynamics)

   Topological materials are of great interest because they can support metallic edge or surface states that are robust against perturbations, with the potential for technological applications. Here, we experimentally explore the light-induced non-equilibrium properties of two distinct topological phases in NaCd4As3: a topological crystalline insulator (TCI) phase and a topological insulator (TI) phase. This material has surface states that are protected by mirror symmetry in the TCI phase at room temperature, while it undergoes a structural phase transition to a TI phase below 200 K. After exciting the TI phase by an ultrafast laser pulse, we observe a leading band edge shift of >150 meV that slowly builds up and reaches a maximum after ∼0.6 ps and that persists for ∼8 ps. The slow rise time of the excited electron population and electron temperature suggests that the electronic and structural orders are strongly coupled in this TI phase. It also suggests that the directly excited electronic states and the probed electronic states are weakly coupled. Both couplings are likely due to a partial relaxation of the lattice distortion, which is known to be associated with the TI phase. In contrast, no distinct excited state is observed in the TCI phase immediately or after photoexcitation, which we attribute to the low density of states and phase space available near the Fermi level. Our results show how ultrafast laser excitation can reveal the distinct excited states and interactions in phase-rich topological materials. 

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5. Transition to an excitonic insulator from a two-dimensional conventional insulator

   https://doi.org/10.1103/PhysRevB.107.075105  

   Manousakis, Efstratios (February 2023, Physical Review B)