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1. Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet

   https://doi.org/10.1126/sciadv.abf1467  

   Asaba, T.; Ivanov, V.; Thomas, S. M.; Savrasov, S. Y.; Thompson, J. D.; Bauer, E. D.; Ronning, F. (March 2021, Science Advances)

   null (Ed.)

   The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCo 0.8 Ru 0.2 Al, reaching 23 microvolts per kelvin. Uranium’s 5 f electrons provide strong electronic correlations that lead to narrow bands, a known route to producing a large thermoelectric response. In addition, uranium’s strong spin-orbit coupling produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that in UCo 0.8 Ru 0.2 Al at least 148 Weyl nodes, and two nodal lines, exist within 60 millielectron volt of the Fermi level. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature. 

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2. Origin of the anisotropic Beer–Lambert law from dichroism and birefringence in β -Ga2O3

   https://doi.org/10.1063/5.0226902  

   Adnan, Md_Mohsinur Rahman; Schubert, Mathias; Myers, Roberto C (August 2024, Applied Physics Letters)

   The anisotropic optical absorption edge of β-Ga2O3 follows a modified Beer–Lambert law having two effective absorption coefficients. The absorption coefficient of linearly polarized light reduces to the least absorbing direction beyond a critical penetration depth, which itself depends on polarization and wavelength. To understand this behavior, a Stokes vector analysis is performed to track the polarization state as a function of depth. The weakening of the absorption coefficient is associated with a gradual shift of linear polarization to the least absorbing crystallographic direction in the plane, which is along the a-exciton within the (010) plane or along the b-exciton in the (001) plane. We show that strong linear dichroism near the optical absorption edge causes this shift in β-Ga2O3, which arises from the anisotropy and spectral splitting of the physical absorbers, i.e., excitons. The linear polarization shift is accompanied by a variation in the ellipticity due to the birefringence of β-Ga2O3. Analysis of the phase relationship between the incoming electric field to that at a certain depth reveals the phase speed as an effective refractive index, which varies along different crystallographic directions. The critical penetration depth is shown to be correlated with the depth at which the ellipticity is maximal. Thus, the anisotropic Beer–Lambert law arises from the interplay of both the dichroic and birefringent properties of β-Ga2O3. 

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3. Large Anomalous and Topological Hall Effect and Nernst Effect in a Dirac Kagome Magnet Fe ₃ Ge

   https://doi.org/10.1002/adfm.202511059  

   Xu, Chunqiang; Gupta, Shuvankar; Tan, Hengxin; Bae, Hyeonhu; Emmanuel, Olajumoke Oluwatobiloba; Xu, Mingyu; Wu, Yan; Xu, Xiaofeng; Zhang, Pengpeng; Xie, Weiwei; et al (October 2025, Advanced Functional Materials)

   Abstract Searching for Kagome magnets with novel magnetic and electronic properties has been attracting significant efforts recently. Here, the magnetic, electronic, and thermoelectric properties of Fe₃Ge single crystals with Fe atoms forming a slightly distorted Kagome lattice are reported. It is shown that Fe₃Ge exhibits a large anomalous Hall effect and anomalous Nernst effect. The observed anomalous transverse thermoelectric conductivity reaches ≈4.6 A m⁻¹ K⁻¹, which is larger than the conventional ferromagnets and most of the topological ferromagnets reported in literature. The first‐principles calculations suggest that these exceptional transport properties are dominated by the intrinsic mechanism, which highlights the significant contribution of the Berry curvature of massive Dirac gaps in the momentum space. Additionally, a topological Hall resistivity of 0.9 µΩ cm and a topological Nernst coefficient of 1.2 µV K⁻¹are also observed, which are presumably ascribed to the Berry phase associated with the field‐induced non‐zero scalar spin chirality. These features highlight the synergic effects of the Berry phases in both momentum space and real space of Fe₃Ge, which render it an excellent candidate for room‐temperature thermoelectric applications based on transverse transport. 

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4. Second order Zeeman interaction and ferroquadrupolar order in TmVO4

   https://doi.org/10.1038/s41535-022-00475-1  

   Vinograd, I.; Shirer, K. R.; Massat, P.; Wang, Z.; Kissikov, T.; Garcia, D.; Bachmann, M. D.; Horvatić, M.; Fisher, I. R.; Curro, N. J. (December 2022, npj Quantum Materials)

   Abstract TmVO 4 exhibits ferroquadrupolar order of the Tm 4f electronic orbitals at low temperatures, and is a model system for Ising nematicity. A magnetic field oriented along the c -axis constitutes a transverse effective field for the quadrupolar order parameter, continuously tuning the system to a quantum phase transition as the field is increased from zero. In contrast, in-plane magnetic fields couple to the order parameter only at second order, such that orienting along the primary axes of the quadrupole order results in an effective longitudinal field, whereas orienting at 45 degrees results in a second effective transverse field. Not only do in-plane fields engender a marked in-plane anisotropy of the critical magnetic and quadrupole fluctuations above the ferroquadrupolar ordering temperature, but in-plane transverse fields initially enhance the ferroquadrupolar order, before eventually suppressing it, an effect that we attribute to admixing of the higher crystalline electric field levels. 

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5. Structural anisotropy in Sb thin films

   https://doi.org/10.1063/5.0159670  

   Adhikari, Pradip; Wijesinghe, Anuradha; Rathore, Anjali; Yoo, Timothy Jinsoo; Kim, Gyehyeon; Yeom, Sinchul; Lee, Hyoung-Taek; Mazza, Alessandro R; Sohn, Changhee; Park, Hyeong-Ryeol; et al (January 2024, APL Materials)

   Sb thin films have attracted wide interest due to their tunable band structure, topological phases, high electron mobility, and thermoelectric properties. We successfully grow epitaxial Sb thin films on a closely lattice-matched GaSb(001) surface by molecular beam epitaxy. We find a novel anisotropic directional dependence on their structural, morphological, and electronic properties. The origin of the anisotropic features is elucidated using first-principles density functional theory (DFT) calculations. The growth regime of crystalline and amorphous Sb thin films was determined by mapping the surface reconstruction phase diagram of the GaSb(001) surface under Sb2 flux, with confirmation of structural characterizations. Crystalline Sb thin films show a rhombohedral crystal structure along the rhombohedral (211) surface orientation parallel to the cubic (001) surface orientation of the GaSb substrate. At this coherent interface, Sb atoms are aligned with the GaSb lattice along the [1̄10] crystallographic direction but are not aligned well along the [110] crystallographic direction, which results in anisotropic features in reflection of high-energy electron diffraction patterns, misfit dislocation formation, surface morphology, and transport properties. Our DFT calculations show that the preferential orientation of the rhombohedral Sb (211) plane may originate from the GaSb surface, where Sb atoms align with the Ga and Sb atoms on the reconstructed surface. The formation energy calculations confirm the stability of the experimentally observed structures. Our results provide optimal film growth conditions for further studies of novel properties of Bi1−xSbx thin films with similar lattice parameters and an identical crystal structure, as well as functional heterostructures of them with III–V semiconductor layers along the (001) surface orientation, supported by a theoretical understanding of the anisotropic film orientation. 

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