Sanjoy Kr Mahatha

High-entropy stabilization chemistry is redefining materials design by transforming configurational disorder, arising from the deliberate incorporation of multiple principal cations, into a thermodynamic advantage that promotes phase stability and enables emergent functionalities. In this work, we investigate the evolution of magnetic ordering in spinel-type high-entropy oxides by systematically varying the cation composition of the B site within a fixed high-entropy A-site matrix (nominal composition), (Ni0.2Mg0.2Co0.2Cu0.2Zn0.2)B2O4. Upon introducing multicomponent B-site configurations, we uncover a strikingly linear dependence of the magnetic transition temperature (TC) on the TCs of the corresponding single-B-site high-entropy systems. Remarkably, this trend persists even in highly complex (Ni0.2Mg0.2Co0.2Cu0.2Zn0.2)(Cr0.2Mn0.2Fe0.2Ga0.2X0.2)2O4, X = Al and Ti. Despite the material’s extremely high degree of disorder and the absence of a dominant magnetic ion or a straightforward superexchange pathway, detailed magnetization measurements, low-temperature X-ray magnetic circular dichroism, and neutron powder diffraction studies reveal robust long-range ferrimagnetic ordering. These results reveal a predictability in ferrimagnetic high-entropy spinel oxides, where, despite extreme configurational disorder and competing interactions, robust ferrimagnetic order can arise from, rather than be hindered by, extreme configurational disorder. This establishes a pathway for predictively tuning magnetic transition temperatures in high-entropy oxides beyond conventional ordered systems.

The parkerite family of ternary transition-metal chalcogenides, with the general formula A 3 M 2 X 2 , exhibits considerable structural diversity and intriguing electronic properties. Within this family, Ni 3 Bi 2 Se 2 has attracted particular interest due to its rich electronic and transport properties. However, its momentum-resolved electronic structure remains largely unexplored. Here, we present a comprehensive experimental and theoretical investigation of Ni 3 Bi 2 Se 2 to elucidate its electronic structure. Structural and transport measurements confirm the high crystalline quality and multiband semimetallic character of the compound, while x-ray photoelectron spectroscopy establishes the elemental composition and chemical states of its constituent elements. Soft x-ray angle-resolved photoemission spectroscopy measurements reveal anisotropic electron- and hole-like Fermi pockets and band dispersions in good agreement with first-principles calculations. Together, these results provide a comprehensive understanding of the electronic structure of Ni 3 Bi 2 Se 2 and offer new insights into the broader class of parkerite compounds.

Nanoscale electronic structure at heterointerfaces critically governs charge-transfer pathways and photocatalytic efficiency, yet direct experimental insight remains limited. Herein, we report an interfacial Z-scheme heterostructure in a porous MXene-Fe3O4@Ag nanocomposite, allowing direct resolution and correlation of nanoscale electronic properties with efficient doxycycline disintegration under ambient solar irradiation. Hybrid integration of plasmonic Ag and magnetic Fe3O4 nanoparticles onto conductive Ti3C2 MXene sheets generates densely coupled heterointerfaces with pronounced electronic reconstruction. Scanning tunneling microscopy and spectroscopy, complemented by Kelvin probe force microscopy, reveal local density-of-states modulation and nanoscale band bending at the MXene-Fe3O4@Ag junctions before and after illumination, while X-ray photoelectron spectroscopy confirms interfacial charge redistribution. Together, these experimental observations provide direct evidence for a Z-scheme charge-transfer architecture. Enabled by this optimized interfacial electronic landscape, the nanocomposite achieves complete doxycycline disintegration with a substantially enhanced apparent quantum yield and significantly reduced solar energy consumption. The photocatalytic performance remains robust in complex real water matrices, including tap water, river water, and wastewater. Reactive species trapping experiments identify •OH radicals as the dominant oxidative species, elucidating the Z-scheme-driven photocatalytic mechanism. This study establishes nanoscale electronic-structure engineering as a key design principle for MXene-based Z-scheme photocatalysts for sustainable pharmaceutical wastewater remediation.

The integration of metallic overlayers with topological semimetals provides a promising route to engineer novel quantum heterostructures while preserving nontrivial electronic states. In this work, we investigate the growth and interfacial electronic structure of Sn deposited on Mo 0.3 W 0.7 Te 2 using low-energy electron diffraction, x-ray photoelectron spectroscopy (XPS), and angle-resolved photoemission spectroscopy (ARPES). We find that Sn forms a quasi-van der Waals overlayer with weak interfacial coupling. XPS measurements show no detectable core-level shifts, indicating a chemically abrupt interface with negligible charge transfer. ARPES reveals that the near-Fermi-level band structure, including the Weyl states, remains largely intact upon Sn deposition, with no significant band reconstruction along the Γ ― – Y ― direction. In contrast, modifications are confined to deeper valence band states, particularly along Γ ― – X ― , reflecting weak, energy-dependent hybridization from Sn-derived states. This energy-selective coupling enables the integration of a metallic overlayer while preserving the symmetry-protected topological states of the substrate. Our results establish a viable route for engineering electronically transparent metal-topological semimetal interfaces and exploring proximity-induced quantum phenomena.

Charge density waves (CDWs) are a canonical interaction-driven electronic phenomenon with potential technological applications, such as collective electronic switching and local information storage. Here, we investigate the properties of the CDW in the mixed-chalcogen compound 1T-TaSeTe using bulk- and surface-sensitive diffraction and spectroscopy techniques and transport measurements. Compared to the pristine parent compound 1T-TaSe2, we find that the incommensurate CDW appears to remain incommensurate down to low temperatures. The CDW-induced gapping of the Fermi surface is pronounced and may explain the observed semiconductor-like electrical resistivity behavior in combination with chalcogen disorder. Our results demonstrate that disordered chalcogen substitution doping can modify, yet preserve, the characteristic emergent electronic properties of a transition metal dichalcogenide.

Tin (Sn) thin films are deposited on BiSe substrate via vapor deposition under ultrahigh vacuum conditions, and the surface electronic structure and interface chemistry are systematically investigated using X‐ray and ultraviolet photoemission spectroscopy (XPS and UPS) measurements. Spectroscopy analysis reveals the formation of SnSe bonds along with a reduction of Bi, leading to the emergence of multiple Sn‐based interfacial phases such as SnSe and SnSe. Thus, our study estabilishes predominance of interfacial chemistry over epitaxial stanene growth on BiSe at room temperature, highlighting the challenges associated with the interface engineering in layered topological systems.