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1. Superconductivity and Pronounced Electron‐Phonon Coupling in Rock‐Salt Al _1−x O _1−x and Ti _1−x O _1−x

   https://doi.org/10.1002/aelm.202400141  

   Žguns, Pjotrs; Gedik, Nuh; Yildiz, Bilge; Li, Ju (May 2024, Advanced Electronic Materials)

   Abstract The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb_1−xO_1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al_1−xO_1−xand Ti_1−xO_1−x(λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc_1−xO_1−xand Nb_1−xO_1−xshow significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti_1−x(O_1−xHx) and Nb_1−x(O_1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure. 

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2. Magnetic moments and spin structure in single-phase B20 Co _1+x Si _1−x (x = 0.043)

   https://doi.org/10.1063/5.0090545  

   Wang, Haohan; Balasubramanian, Balamurugan; Liu, Yaohua; Streubel, Robert; Pahari, Rabindra; Ekanayaka, Thilini Kumari; Mishra, Esha; Klewe, Christoph; Shafer, Padraic; Dhall, Rohan; et al (May 2022, Journal of Applied Physics)

   Neutron powder diffraction (NPD) and x-ray magnetic circular dichroism (XMCD) spectroscopy are employed to investigate the magnetism and spin structure in single-phase B20 Co 1.043 Si 0.957 . The magnetic contributions to the NPD data measured in zero fields are consistent with the helical order among the allowed spin structures derived from group theory. The magnitude of the magnetic moment is (0.3 ± 0.1) μ B /Co according to NPD, while the surface magnetization probed by XMCD at 3 kOe is (0.18–0.31) μ B /Co. Both values are substantially larger than the bulk magnetization of 0.11 μ B /Co determined from magnetometry at 70 kOe and 2 K. These experimental data indicate the formation of a helical spin phase and the associated conical states in high magnetic fields. 

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3. Phase stability and mechanical properties of Mo _{1- x} N _x with 0 ≤ x ≤ 1

   https://doi.org/10.1063/1.4998686  

   Balasubramanian, Karthik; Huang, Liping; Gall, Daniel (November 2017, Journal of Applied Physics)
4. Bandgap engineering in quasi-1D Zr _1−x Ti _x S ₃ (0 ≤ x ≤ 1) solid solutions

   https://doi.org/10.1039/d5tc02480c  

   Muratov, Dmitry S; Bianco, Ettore; Karpenkov, Dmitry; Castellero, Alberto; Lipatov, Alexey; Maurino, Valter; Sinitskii, Alexander (January 2025, Journal of Materials Chemistry C)

   We synthesized a series of Zr_1−xTi_xS₃solid solutions (0 ≤x≤ 1)viaa direct reaction between Zr–Ti alloys and sulfur vapor at 600 °C. These solid solutions have a tunable bandgap in the 1–2 eV range that linearly increases with the Zr content. 

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5. High-magnetic-field phases in U _1-x Th _x Te ₂

   https://doi.org/10.1073/pnas.2521261122  

   Moir, Camilla M; Singleton, John; Blawat, Joanna; Lee-Wong, Eric; Deng, Yuhang; Feng, Keke; Wannamaker, Tyler; Baumbach, Ryan E; Maple, M Brian (October 2025, Proceedings of the National Academy of Sciences)

   At temperaturesTmuch lower than its superconducting critical temperatureT_c= 2.1 K, the heavy fermion superconductor UTe₂has a unique phase diagram of magnetic fieldHvs. φ and θ, anglesHis tilted from theb-axis toward thea- andc-axes, respectively, of its orthorhombic unit cell. The phase diagram contains three distinct superconducting phases: SC₁in which φ and θ extend from 0 to 90° andH≤ ~15 T; SC₂for φ ≤ ~7°, θ ≤ ~4° and ~15 T ≤H≤H_m= ~35 T, the onset of the magnetic field polarized (FP) phase, and SC_FPwhich resides entirely within the FP phase in a pocket of superconductivity extending from θ ≈ 20° to 40° and from ~40 T to above 60 T. We studied the evolution of theHvs. θ phase diagram for Th concentrations 0.005 ≤x≤ 0.047 in the U_1-xTh_xTe₂system at ~0.6 K. Within this range ofxvalues, SC₁extends over 0 ≤ θ ≤ 90° andH≤ ~10 T forx= 0.047, while SC₂is suppressed. The SC_FPand FP phases are unaffected tox= 0.02 but are completely suppressed in the regionx= 0.025 to 0.047 where the residual resistance ratioRRR~3 indicates a significant amount of disorder. These results complement recent studies of nonsuperconducting disordered UTe₂single crystals in which the SC₁and SC₂phases are absent, but the FP and so-called “orphan” SC_FPphases are retained. 

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