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1. Spin structure and dynamics of the topological semimetal Co3Sn2-xInxS2

   https://doi.org/10.1038/s41535-022-00523-w  

   Neubauer, Kelly J.; Ye, Feng; Shi, Yue; Malinowski, Paul; Gao, Bin; Taddei, Keith M.; Bourges, Philippe; Ivanov, Alexandre; Chu, Jiun-Haw; Dai, Pengcheng (December 2022, npj Quantum Materials)

   Abstract The anomalous Hall effect (AHE), typically observed in ferromagnetic (FM) metals with broken time-reversal symmetry, depends on electronic and magnetic properties. In Co₃Sn_2-xIn_xS₂, a giant AHE has been attributed to Berry curvature associated with the FM Weyl semimetal phase, yet recent studies report complicated magnetism. We use neutron scattering to determine the spin dynamics and structures as a function ofxand provide a microscopic understanding of the AHE and magnetism interplay. Spin gap and stiffness indicate a contribution from Weyl fermions consistent with the AHE. The magnetic structure evolves fromc-axis ferromagnetism at$$x = 0$$ $x=0$to a canted antiferromagnetic (AFM) structure with reducedc-axis moment and in-plane AFM order at$$x = 0.12$$ $x=0.12$and further reducedc-axis FM moment at$$x = 0.3$$ $x=0.3$. Since noncollinear spins can induce non-zero Berry curvature in real space acting as a fictitious magnetic field, our results revealed another AHE contribution, establishing the impact of magnetism on transport. 

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2. Enhancement of Curie temperature in ferromagnetic insulator-topological insulator heterostructures

   https://doi.org/10.1088/1361-6633/ae3982  

   Mirzhalilov, Murod; Trivedi, Nandini; Randeria, Mohit (January 2026, Reports on Progress in Physics)

   Abstract We theoretically analyze the topological insulator (TI) surface state mediated interactions between local moments in a proximate 2D ferromagnetic insulator (FMI) motivated by recent experiments that show a significant increase in the Curie temperature $T_{\mathrm{c}}$of FMI-TI heterostructures. Such interactions have been investigated earlier with a focus on dilute magnetic dopants in TIs. Our problem involves a dense set of moments for which we find that the short range Bloembergen–Rowland interaction, arising from virtual particle-hole transitions between the valence and conduction bands, dominates over the oscillatory Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction. We show that the $T_{\mathrm{c}}$enhancement is proportional to the Van Vleck susceptibility and that the spin-momentum locking of surface states leads to out-of-plane ferromagnetic order in the FMI. We investigate how the hybridization between top and bottom surfaces in a thin TI film impacts $T_{\mathrm{c}}$enhancement, and show how our results can help understand recent experiments on atomically thin Cr₂Te₃-(Bi,Sb)₂Te₃. Our results advance the understanding of magnetic interactions relevant for TI-based spintronic and magnonic devices. 

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3. Regarding the existence of abelian fractional topological insulators in twisted MoTe2 and related systems

   https://doi.org/10.1038/s42005-025-02483-6  

   Kwan, Yves H; Wagner, Glenn; Yu, Jiabin; Dagnino, Andrea Kouta; Jiang, Yi; Xu, Xiaodong; Bernevig, B Andrei; Neupert, Titus; Regnault, Nicolas (December 2026, Communications Physics)

   Abstract The experimental discovery of fractional Chern insulators (FCIs) in moiré materials raises the question of whether their time-reversal invariant analogs, fractional topological insulators (FTIs), can also be realized in these platforms. We address this via exact diagonalization calculations in both a Landau level (LL) model and continuum model for twisted MoTe₂, and extract principles for engineering FTIs in realistic conditions. For the spinful LL model at filling$$\nu =\frac{1}{3}+\frac{1}{3}$$ $\nu =\frac{1}{3}+\frac{1}{3}$, we show that a suppression of the short-range component of the interaction is important to stabilize the FTI. For twisted MoTe₂at$$\nu =-\frac{4}{3}$$ $\nu =-\frac{4}{3}$, we find that a short-range attractiongon top of the screened Coulomb interaction is needed to realize an FTI. We discuss how this threshold value ofgcould be reduced by examining larger system sizes, incorporating band-mixing effects, exploiting Landau level character, and engineering the dielectric environment. While our study highlights the challenges, at least for the fillings considered, for obtaining FTIs, we also provide potential sample-engineering routes to improve the stability of FTI phases. 

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4. High-pressure induced Weyl semimetal phase in 2D Tellurium

   https://doi.org/10.1038/s42005-023-01460-1  

   Niu, Chang; Zhang, Zhuocheng; Graf, David; Lee, Seungjun; Wang, Mingyi; Wu, Wenzhuo; Low, Tony; Ye, Peide D. (December 2023, Communications Physics)

   Abstract Relativistic Weyl fermion quasiparticles in Weyl semimetal bring the electron’s chirality degree of freedom into the electrical transport and give rise to exotic phenomena. A topological phase transition from a topological trivial phase to a topological non-trivial phase offers a route to control electronic devices through its topological properties. Here, we report the Weyl semimetal phase in hydrothermally grown two-dimensional Tellurium (2D Te) induced by high hydrostatic pressure (up to 2.47 GPa). The unique chiral crystal structure gives rise to chiral fermions with different topological chiral charges ($${{C}}=-{{1}},+{{1}},{{and}}-{{2}}$$ $C=-1,+1,and-2$). The highly tunable chemical potential in 2D Te provides comprehensive information for understanding the pressure-dependent electron band structure. The pressure-induced insulator-to-metal transition, two-carrier transport, and the non-trivial π Berry phase shift in quantum oscillations are observed in the 2D Te Weyl semimetal phase. Our work demonstrates the pressure-induced bandgap closing in the inversion asymmetric narrow bandgap semiconductor 2D Te. 

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5. Highly-excited Rydberg excitons in synthetic thin-film cuprous oxide

   https://doi.org/10.1038/s41598-023-41465-y  

   DeLange, Jacob; Barua, Kinjol; Paul, Anindya Sundar; Ohadi, Hamid; Zwiller, Val; Steinhauer, Stephan; Alaeian, Hadiseh (December 2023, Scientific Reports)

   Abstract Cuprous oxide ($$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$) has recently emerged as a promising material in solid-state quantum technology, specifically for its excitonic Rydberg states characterized by large principal quantum numbers (n). The significant wavefunction size of these highly-excited states (proportional to$$n^2$$ $n^2$) enables strong long-range dipole-dipole (proportional to$$n^4$$ $n^4$) and van der Waals interactions (proportional to$$n^{11}$$ $n^{11}$). Currently, the highest-lying Rydberg states are found in naturally occurring$$\hbox {Cu}_2\hbox {O}$$ ${\text{Cu}}_2\text{O}$. However, for technological applications, the ability to grow high-quality synthetic samples is essential. The fabrication of thin-film$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$samples is of particular interest as they hold potential for observing extreme single-photon nonlinearities through the Rydberg blockade. Nevertheless, due to the susceptibility of high-lying states to charged impurities, growing synthetic samples of sufficient quality poses a substantial challenge. This study successfully demonstrates the CMOS-compatible synthesis of a$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$thin film on a transparent substrate that showcases Rydberg excitons up to$$n = 8$$ $n=8$which is readily suitable for photonic device fabrications. These findings mark a significant advancement towards the realization of scalable and on-chip integrable Rydberg quantum technologies. 

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