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1. Electronic anisotropy and rotational symmetry breaking at a Weyl semimetal/spin ice interface

   https://doi.org/10.1126/sciadv.adr6202  

   Wu, Tsung-Chi; Chang, Yueqing; Wu, Ang-Kun; Terilli, Michael; Wen, Fangdi; Kareev, Mikhail; Choi, Eun Sang; Graf, David; Zhang, Qinghua; Gu, Lin; et al (June 2025, Science Advances)

   In magnetic pyrochlore materials, the interplay of spin-orbit coupling, electronic correlations, and geometrical frustration gives rise to exotic quantum phases, including topological semimetals and spin ice. While these phases have been observed in isolation, the interface-driven phenomena emerging from their interaction have never been realized previously. Here, we report on the discovery of interfacial electronic anisotropy and rotational symmetry breaking at a heterostructure consisting of the Weyl semimetal Eu₂Ir₂O₇and spin ice Dy₂Ti₂O₇. Subjected to magnetic fields, we unveil a sixfold anisotropic transport response that is theoretically accounted by a Kondo-coupled heterointerface, where the spin ice’s field-tuned magnetism induces electron scattering in the Weyl semimetal’s topological Fermi-arc states. Furthermore, at elevated magnetic fields, we reveal a twofold anisotropic response indicative of the emergence of a symmetry-broken many-body state. This discovery showcases the potential of pyrochlore frustrated magnet/topological semimetal heterostructures in search of emergent interfacial phenomena. 

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2. Interplay between Kondo and magnetic interactions in Pr0.75Gd0.25ScGeH

   https://doi.org/10.1016/j.jallcom.2023.171351  

   Del Rose, Tyler; Choudhary, Renu; Mudryk, Yaroslav; Haskel, Daniel; Pathak, Arjun K.; Bhaskar, Gourab; Zaikina, Julia V.; Johnson, Duane D.; Pecharsky, Vitalij K. (December 2023, Journal of Alloys and Compounds)

   Combined experimental and density functional theory (DFT) study of Pr0.75Gd0.25ScGe and its hydride (Pr0.75Gd0.25ScGeH) reveals intricacies of composition-structure-property relationships in those distinctly layered compounds. Hydrogenation of the intermetallic parent, crystalizing in a tetragonal CeScSi-type structure, leads to an anisotropic volume expansion, that is, a(=b) lattice parameter decreases while the lattice expands along the c direction, yielding a net increase of cell volume. DFT calculations predict an antiparallel coupling of localized Gd and Pr magnetic moments in both materials at the ground state. While experiments corroborate this for the parent compound, there is no conclusive experimental proof for the hydride, where Pr moments do not order down to 3 K. DFT results also reveal that rare-earth – hydrogen interactions reduce spin-polarization of the Pr and Gd 5d and Sc 3d states at the Fermi energy, disrupt indirect exchange interactions mediated by conduction electrons, dramatically reduce the magnetic ordering temperature, and open a pseudo-gap in the majority-spin channel. Both experiments and theory show evidence of Kondo-like behavior in the hydride in the absence of an applied magnetic field, whereas increasing the field promotes magnetic ordering and suppresses Kondo-like behavior. 

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3. Resonant nanodiffraction x-ray imaging reveals role of magnetic domains in complex oxide spin caloritronics

   https://doi.org/10.1126/sciadv.aba9351  

   Evans, Paul G.; Marks, Samuel D.; Geprägs, Stephan; Dietlein, Maxim; Joly, Yves; Dai, Minyi; Hu, Jiamian; Bouchenoire, Laurence; Thompson, Paul B.; Schülli, Tobias U.; et al (October 2020, Science Advances)

   null (Ed.)

   Spin electronic devices based on crystalline oxide layers with nanoscale thicknesses involve complex structural and magnetic phenomena, including magnetic domains and the coupling of the magnetism to elastic and plastic crystallographic distortion. The magnetism of buried nanoscale layers has a substantial impact on spincaloritronic devices incorporating garnets and other oxides exhibiting the spin Seebeck effect (SSE). Synchrotron hard x-ray nanobeam diffraction techniques combine structural, elemental, and magnetic sensitivity and allow the magnetic domain configuration and structural distortion to be probed in buried layers simultaneously. Resonant scattering at the Gd L 2 edge of Gd 3 Fe 5 O 12 layers yields magnetic contrast with both linear and circular incident x-ray polarization. Domain patterns facet to form low-energy domain wall orientations but also are coupled to elastic features linked to epitaxial growth. Nanobeam magnetic diffraction images reveal diverse magnetic microstructure within emerging SSE materials and a strong coupling of the magnetism to crystallographic distortion. 

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4. Field-induced quantum critical point in the itinerant antiferromagnet Ti3Cu4

   https://doi.org/10.1038/s42005-022-00901-7  

   Moya, Jaime M.; Hallas, Alannah M.; Loganathan, Vaideesh; Huang, C. -L.; Kish, Lazar L.; Aczel, Adam A.; Beare, J.; Cai, Y.; Luke, G. M.; Weickert, Franziska; et al (May 2022, Communications Physics)

   Abstract New phases of matter emerge at the edge of magnetic instabilities, which can occur in materials with moments that are localized, itinerant or intermediate between these extremes. In local moment systems, such as heavy fermions, the magnetism can be tuned towards a zero-temperature transition at a quantum critical point (QCP) via pressure, chemical doping, and, rarely, magnetic field. By contrast, in itinerant moment systems, QCPs are more rare, and they are induced by pressure or doping; there are no known examples of field induced transitions. This means that no universal behaviour has been established across the whole itinerant-to-local moment range—a substantial gap in our knowledge of quantum criticality. Here we report an itinerant antiferromagnet, Ti₃Cu₄, that can be tuned to a QCP by a small magnetic field. We see signatures of quantum criticality and the associated non-Fermi liquid behaviour in thermodynamic and transport measurements, while band structure calculations point to an orbital-selective, spin density wave ground state, a consequence of the square net structural motif in Ti₃Cu₄. Ti₃Cu₄thus provides a platform for the comparison and generalisation of quantum critical behaviour across the whole spectrum of magnetism. 

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5. Observation of momentum-dependent charge density wave gap in a layered antiferromagnet GdTe3

   https://doi.org/10.1038/s41598-023-44851-8  

   Regmi, Sabin; Bin Elius, Iftakhar; Sakhya, Anup Pradhan; Jeff, Dylan; Sprague, Milo; Mondal, Mazharul Islam; Jarrett, Damani; Valadez, Nathan; Agosto, Alexis; Romanova, Tetiana; et al (December 2023, Scientific Reports)

   Abstract Charge density wave (CDW) ordering has been an important topic of study for a long time owing to its connection with other exotic phases such as superconductivity and magnetism. The$$R{\textrm{Te}}_{3}$$ $R{\text{Te}}_3$(R= rare-earth elements) family of materials provides a fertile ground to study the dynamics of CDW in van der Waals layered materials, and the presence of magnetism in these materials allows to explore the interplay among CDW and long range magnetic ordering. Here, we have carried out a high-resolution angle-resolved photoemission spectroscopy (ARPES) study of a CDW material$${\textrm{Gd}}{\textrm{Te}}_{3}$$ $\text{Gd}{\text{Te}}_3$, which is antiferromagnetic below$$\sim \mathrm {12~K}$$ $\sim 12K$, along with thermodynamic, electrical transport, magnetic, and Raman measurements. Our ARPES data show a two-fold symmetric Fermi surface with both gapped and ungapped regions indicative of the partial nesting. The gap is momentum dependent, maximum along$${\overline{\Gamma }}-\mathrm{\overline{Z}}$$ $\overline{\Gamma }-\overline{Z}$and gradually decreases going towards$${\overline{\Gamma }}-\mathrm{\overline{X}}$$ $\overline{\Gamma }-\overline{X}$. Our study provides a platform to study the dynamics of CDW and its interaction with other physical orders in two- and three-dimensions. 

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