Search

Heavy-fermion metals are prototype systems for observing emergent quantum phases driven by electronic interactions1–6. A long-standing aspiration is the dimensional reduction of these materials to exert control over their quantum phases7–11, which remains a significant challenge because traditional intermetallic heavy-fermion compounds have three-dimensional atomic and electronic structures. Here we report comprehensive thermodynamic and spectroscopic evidence of an antiferromagnetically ordered heavy-fermion ground state in CeSiI, an intermetallic comprising two-dimensional (2D) metallic sheets held together by weak interlayer van der Waals (vdW) interactions. Owing to its vdW nature, CeSiI has a quasi-2D electronic structure, and we can control its physical dimension through exfoliation. The emergence of coherent hybridization of fand conduction electrons at low temperature is supported by the temperature evolution of angle-resolved photoemission and scanning tunnelling spectra near the Fermi level and by heat capacity measurements. Electrical transport measurements on few-layer flakes reveal heavy-fermion behaviour and magnetic order down to the ultra-thin regime. Our work establishes CeSiI and related materials as a unique platform for studying dimensionally confined heavy fermions in bulk crystals and employing 2D device fabrication techniques and vdW heterostructures12to manipulate the interplay between Kondo screening, magnetic order and proximity effects.

Electronic correlation effects are manifested in quantum materials when either the on-site Coulomb repulsion is large or the electron kinetic energy is small. The former is the dominant effect in cuprate superconductors and heavy-fermion systems whereas it is the latter in twisted bilayer graphene and geometrically frustrated metals. However, the simultaneous cooperation of both effects in the same quantum material remains rare. The design aim is to produce correlated topological flat bands pinned at the Fermi level. Here, we observe a flat band at the Fermi level in a 3dpyrochlore metal CuV2S4. Our angle-resolved photoemission spectroscopy data reveal that destructive quantum interference associated with the V pyrochlore sublattice and further renormalization to the Fermi level by electron interactions induce this flat band. Consequently, we discover transport signatures that evidence a deviation from Fermi liquid behaviour as well as an enhanced Sommerfeld coefficient. Our work illustrates the combined cooperation of local Coulomb interactions and geometric frustration in a pyrochlore lattice system to induce correlated topology by constructing and pinning correlated flat bands near the Fermi level.

Here, we present a family of titanium-based kagome metals of the form LnTi3Bi4(Ln: La···Gd3+, Eu2+, Yb2+). Four previously unreported compounds are presented: YbTi3Bi4, GdTi3Bi4, NdTi3Bi4, and PrTi3Bi4. Single-crystal growth methods are provided alongside detailed magnetic and thermodynamic measurements across the entire series. The LnTi3Bi4family of compounds are orthorhombic (Fmmm), layered compounds that exhibit slightly distorted titanium-based kagome nets interwoven with zigzag lanthanide-based (Ln) chains. Crystals are easily exfoliated parallel to the kagome sheets, and angular resolved photoemission (ARPES) measurements highlight the intricacy of the electronic structure in these compounds. Density functional theory (DFT) and ARPES studies find Dirac points near the Fermi level, consistent with the kagome-derived band structure. The magnetic properties and the associated anisotropy emerge from the quasi-1D zigzag chains of Ln and impart a wide array of magnetic ground states ranging from anisotropic ferromagnetism to complex antiferromagnetism with a cascade of metamagnetic transitions. The combination of the kagome-based electronic structure and highly anisotropic Ln-based magnetism on an exfoliatable platform cements the LnTi3Bi4family as an interesting addition to the ever-expanding suite of kagome metals.

As a two-dimensional structural motif, the kagome net produces many interesting magnetic and electronic properties. In particular, this lattice produces flat electronic bands with a large density of states. When the chemical potential is positioned within these flat bands, electronic instabilities can result. For the kagome metal CoSn, this alignment is not realized, the flat bands are completely filled, and the compound is a Pauli paramagnet. We have grown crystals and powders of CoSn1 – xInxand shown that replacing Sn with In moves the chemical potential into the flat band region, as expected from simple electron counting. This is supported by band structure calculations, heat capacity measurements, and angle-resolved photoemission spectroscopy. The increased density of states results in the emergence of antiferromagnetic order evidenced by magnetic susceptibility, Mössbauer spectroscopy, and neutron diffraction data. The Néel temperature reaches a maximum of 32 K. The emergence of magnetic order when introducing a nonmagnetic element into a nonmagnetic kagome metal is striking. This work provides clear evidence that flat bands arising from electronically frustrated lattices in bulk crystals provide a new and powerful way to realize correlated ground states controlled by crystal chemistry.

Oxidative stress has a key role in the pathogenesis of diabetes-induced cataract formation and nephropathy. Daily moderate exercise and vitamins C and E (VCE) supplementation can be beneficial to diabetes due to reducing blood glucose and free radical production The aim of this study was to analyze the effect of moderate exercise with vitamin VCE on lipid peroxidation (LP) and antioxidative systems in the kidneys and lens of streptozotocin-induced diabetic rats. Forty female Wistar rats were used. They were randomly divided into four groups. The first and second groups were used as control and diabetic groups. The third group was the diabetic-exercise group. VCE-supplemented feed was given to diabetic-exercise rats constituting the fourth group. Animals in the exercised groups were moderately exercised daily on a treadmill for three weeks (five days a week). Diabetes was induced on day zero of exercise. Body weights in the four groups were recorded weekly. Lens and kidney samples were taken from all animals on day 20. Glutathione peroxidase (GSH-Px), reduced glutathione (GSH), vitamin E, and β-carotene levels in kidney and lens, albumin in plasma, and body weight were significantly lower in the diabetic group than in the control group, whereas there was a significant increase in LP of kidney and lens as well as plasma glucose, urea, and creatinine levels in the diabetic group. The decrease in antioxidant enzymes, vitamins, and albumin and the increase in LP and glucose levels in diabetic rats were significantly improved with exercise and VCE supplementation. In the diabetic animals, the decreased β-carotene and vitamins A levels in kidney did not improve through exercise only, although their levels were increased by exercise plus VCE supplementation. In conclusion, these data demonstrate that lipid peroxidation increases in the lens and kidney of diabetic animals and this could be due to decreases in antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system through the reduction of ROS and blood glucose levels. The VCE supplementations with exercise may play a role in preventing the development of diabetic nephropathy and cataract formation in diabetic animals.

Seven patients (4 men and 3 women, ranging in age from 27 to 64 years) with pigmented paravenous retinochoroidal atrophy, a rare disorder of unknown origin, were studied. The mean follow-up time was 18.5 months. Fundus examinations were performed, and color fundus photographs were taken. In addition to fluorescein angiography, visual field examinations, color vision and electroretinographic tests were performed. All 7 patients were asymptomatic, with visual acuities ranging from 3/10 to 10/10. Both fundi showed patches of retinochoroidal atrophy and pigmentation along the retinal veins in all patients. Fluorescein angiography showed hyperfluorescence due to the pigment epithelial atrophy together with hypofluorescence corresponding to bone spicule pigment clumping. Visual field tests showed scotomas corresponding with areas of atrophy along the retinal veins. The electroretinography showed reduced responses in 2 cases. Color vision was normal in all cases. The patients had no history of trauma or a previous inflammatory process. Serology for syphilis, Toxoplasmaand cytomegalovirus as well as a skin test for tuberculosis were negative. When the patients were seen at the end of the follow-up period, no variation of the findings was noted. Although the fundus abnormalities can be mild or severe, retinal function tests indicated that this is a geographic and not a generalized disorder.

Co3In2S2is a shandite phase closely related to the ferromagnetic Weyl semimetal Co3Sn2S2and contains Co atoms on an ideal kagomé net. Elemental substitutions in Co3Sn2S2have been shown to invariably suppress its magnetism, and it remains a rare example of a shandite phase with magnetic order. Here, we report a new magnetic shandite compound discovered by substituting Fe into Co3In2S2. Single crystals of (Co1–xFex)3In2S2were grown, and neutron diffraction, ac and dc magnetization, and heat capacity measurements reveal long-range antiferromagnetic order with an interesting noncollinear structure and transition temperatures from 11 to 17 K. Partially substituting Fe for Co was inspired by calculated electronic structures, which suggest that Co3In2S2is near a magnetic instability and shows a peak in the density of states that can be approached by hole doping. While the focus of the present work is primarily on magnetism, there is a nodal ring below the Fermi energy in Co3In2S2that may also provide interest from a topological perspective. Potentially related to this, we find large, linear, nonsaturating magnetoresistance in this compound. This work expands the scope of magnetic topological materials among shandites and motivates similar chemical manipulation studies to reveal hidden magnetic instabilities in this important family and other topological systems.