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1. Neutron scattering study of the kagome metal Sc3Mn3Al7Si5

   Li, X Y; Reig-i-Plessis, D; Liu, P F; Wu, S; Wang, B T; Hallas, A M; Stone, M B; Broholm, C; Aronson, M C (October 2021, Physical review)

   null (Ed.)

   Sc 3 Mn 3 Al 7 Si 5 is a rare example of a correlated metal in which the Mn moments form a kagome lattice. The absence of magnetic ordering to the lowest temperatures suggests that geometrical frustration of magnetic interactions may lead to strong magnetic fluctuations. We have performed inelastic neutron scattering measurements on Sc 3 Mn 3 Al 7 Si 5 , finding that phonon scattering dominates for energies from ∼20–50 meV. These results are in good agreement with ab initio calculations of the phonon dispersions and densities of states, and as well reproduce the measured specific heat. A weak magnetic signal was detected at energies less than ∼10 meV, present only at the lowest temperatures. The magnetic signal is broad and quasielastic, as expected for metallic paramagnets 

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2. The anomalous temperature dependent low energy electron diffraction intensity at epitaxial Sr ₃ Ir ₂ O ₇ thin film surfaces

   https://doi.org/10.1088/1361-648X/adbaa8  

   Adegbite, Peace Ikeoluwa; Subedi, Arjun; Zhang, Yuanyuan; Hong, Xia; Komesu, Takashi; Dowben, P A (March 2025, Journal of Physics: Condensed Matter)

   Abstract We report on the temperature dependent low energy electron diffraction (LEED) studies of 12 nm epitaxial Sr₃Ir₂O₇(001) thin films. The Debye temperature has been extracted from the temperature-dependence of LEED intensity at elevated temperatures and different electron kinetic energies. For the most surface sensitive LEED, obtained at the lowest electron kinetic energies, the extracted surface Debye temperature is 270 ± 22 K, which is much lower than the 488 ± 40 K Debye temperature obtained using higher electron kinetic energies. Surprisingly, the LEED diffraction intensity, at the lowest electron kinetic energies, increases rather than decreases, with increasing sample temperatures up to about 440 K. This anomalous behavior has been attributed to the reduction of the lattice vibrational amplitudes along the surface normal. This damping of the normal mode vibrations with increasing temperature results from the enhanced electronic screening via thermally activated carriers. This scenario is corroborated by the transport measurement, showing that Sr₃Ir₂O₇is a narrow band Mott insulator with a band gap of about 32 meV. We have identified criteria for finding anomalous scattering behavior in other transition metal oxide systems. 

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3. Enhanced near-infrared absorption in lattice-matched Sc _0.14 Al _0.86 N/GaN multi-quantum wells: growth optimization and insights into polarization parameters

   https://doi.org/10.1364/OME.545820  

   Abdin, Zain Ul; Gopakumar, Govardan; Kumar, Rajendra; Manfra, Michael J; Malis, Oana (January 2025, Optical Materials Express)

   We report on the near-infrared intersubband (ISB) absorption properties of strain-free Sc_0.14Al_0.86N/GaN multiple quantum wells (MQWs) grown on c-plane GaN substrates by molecular beam epitaxy. These MQWs exhibit strong, sharp, and tunable absorption energies between 515 meV and 709 meV, for well widths ranging from 7 nm to 1.5 nm, respectively. Observation of ISB absorption in ultra-thin Sc_0.14Al_0.86N/GaN MQWs not only extends the near-infrared range accessible with Sc-containing nitrides but also highlights the challenges of growing nanometer-thick GaN quantum wells. We explore the effects of growth temperature on absorption characteristics and find that substrate temperatures above 600°C significantly enhance ISB absorption intensity but also introduce an energy redshift for the narrowest wells. The redshift is attributed to increased interface roughness due to ScAlN surface morphology degradation at higher temperatures. Additionally, a comparison of experimental results with simulated band-structures indicates that the magnitude of net polarization rises faster with Sc-composition than previously suggested by theoretical calculations. This study advances the prospects of ScAlN/GaN heterostructures for novel photonic devices in the technologically important near-infrared range. 

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4. Remote surface optical phonon scattering in ferroelectric Ba _0.6 Sr _0.4 TiO ₃ gated graphene

   https://doi.org/10.1063/5.0106939  

   Chen, Hanying; Li, Tianlin; Hao, Yifei; Rajapitamahuni, Anil; Xiao, Zhiyong; Schoeche, Stefan; Schubert, Mathias; Hong, Xia (October 2022, Journal of Applied Physics)

   We report the effect of remote surface optical (RSO) phonon scattering on carrier mobility in monolayer graphene gated by ferroelectric oxide. We fabricate monolayer graphene transistors back-gated by epitaxial (001) Ba 0.6 Sr 0.4 TiO 3 films, with field effect mobility up to 23 000 cm 2  V −1  s −1 achieved. Switching ferroelectric polarization induces nonvolatile modulation of resistance and quantum Hall effect in graphene at low temperatures. Ellipsometry spectroscopy studies reveal four pairs of optical phonon modes in Ba 0.6 Sr 0.4 TiO 3 , from which we extract RSO phonon frequencies. The temperature dependence of resistivity in graphene can be well accounted for by considering the scattering from the intrinsic longitudinal acoustic phonon and the RSO phonon, with the latter dominated by the mode at 35.8 meV. Our study reveals the room temperature mobility limit of ferroelectric-gated graphene transistors imposed by RSO phonon scattering. 

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5. Measurement of the solar neutrino interaction rate below 3.49 MeV in Super-Kamiokande-IV

   https://doi.org/10.1103/yz79-h758  

   Yankelevich, A; Abe, K; Asaoka, Y; Harada, M; Hayato, Y; Hiraide, K; Hung, T H; Hosokawa, K; Ieki, K; Ikeda, M; et al (June 2026, Physical Review D)

   Super-Kamiokande (SK) has observed ${}^8\mathrm{B}$ solar neutrino elastic scattering at recoil electron kinetic energies ( $E_{\mathrm{kin}}$ ) as low as 3.49 MeV to study neutrino flavor conversion within the Sun. At SK-observable energies, these conversions are dominated by the Mikheyev-Smirnov-Wolfenstein effect. An upturn in the electron neutrino survival probability in which vacuum neutrino oscillations become dominant is predicted to occur at lower energies, but radioactive background increases exponentially with decreasing energy. New machine learning approaches provide substantial background reduction below 3.49 MeV such that statistical extraction of solar neutrino interactions becomes feasible. This article presents an analysis of the solar neutrino interaction rate at $E_{\mathrm{kin}}<3.49\mathrm{MeV}$ with the full SK-IV period, using data from a wideband intelligent trigger when available and with a boosted decision tree for event selection. A solar neutrino signal is observed between $2.99\mathrm{MeV}<E_{\mathrm{kin}}<3.49\mathrm{MeV}$ with $2.76\sigma$ significance and a data to unoscillated Monte Carlo ratio of ${0.307}_{-0.111}^{+0.112}$ . These additional low-energy data have a negligible effect on the $1\sigma$ intervals of the fits to the solar neutrino energy spectrum but have a noticeable effect on the best fit when using the exponential parametrization. 

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