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1. Angle-Resolved Photoemission Study on the Band Structure of Organic Single Crystals

   https://doi.org/10.3390/cryst10090773  

   Wang, Ke; Ecker, Ben; Gao, Yongli (September 2020, Crystals)

   null (Ed.)

   Angle-resolved photoemission spectroscopy (ARPES) is a vital technique, collecting data from both the energy and momentum of photoemitted electrons, and is indispensable for investigating the electronic band structure of solids. This article provides a review on ARPES studies of the electronic band structure of organic single crystals, including organic charge transfer conductors; organic semiconductors; and organo-metallic perovskites. In organic conductors and semiconductors, band dispersions are observed that are highly anisotropic. The Van der Waals crystal nature, the weak electron wavefunction overlap, as well as the strong electron-phonon coupling result in many organic crystals having indiscernible dispersion. In comparison, organo-metallic perovskite halides are characterized by strong s-p orbitals from the metal and halide at the top of the valence bands, with dispersions similar to those in inorganic materials. 

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2. Dynamical stabilization in delafossite nitrides for solar energy conversion

   https://doi.org/10.1039/c8ta07536k  

   Szymanski, N. J.; Walters, L. N.; Hellman, O.; Gall, D.; Khare, S. V. (October 2018, Journal of Materials Chemistry A)

   Delafossite structured ternary nitrides, ABN 2 , have been of recent experimental investigation for applications such as tandem solar and photoelectrochemical cells. We present a thorough first principles computational investigation of their stability, electronic structure, and optical properties. Nine compounds, where A = Cu, Ag, Au and B = V, Nb, Ta, were studied. For three of these compounds, CuTaN 2 , CuNbN 2 , and AgTaN 2 , our computations agree well with experimental results. Optimized lattice parameters, formation energies, and mechanical properties have been computed using the generalized gradient approximation (GGA). Phonon density of states computed at zero-temperature shows that all compounds are dynamically unstable at low temperatures. Including finite-temperature anharmonic effects stabilizes all compounds at 300 K, with the exception of AgVN 2 . Analysis of Crystal Orbital Hamiltonian Populations (COHP) provides insight into the bonding and antibonding characters of A–N and B–N pairs. Instability at low temperatures can be attributed to strong A–N antibonding character near the Fermi energy. B–N bonding is found to be crucial in maintaining stability of the structure. AgVN 2 is the only compound to display significant B–N antibonding below the Fermi energy, as well as the strongest degree of A–N antibonding, both of which provide explanation for the sustained instability of this compound up to 900 K. Hybrid functional calculations of electronic and optical properties show that real static dielectric constants in the semiconductors are related to corresponding band gaps through the Moss relation. CuTaN 2 , CuNbN 2 , AgTaN 2 , AgNbN 2 , AgVN 2 , AuTaN 2 , and AuNbN 2 exhibit indirect electronic band gaps while CuVN 2 and AuVN 2 are metallic. Imaginary parts of the dielectric function are characterized by d–d interband transitions in the semiconductors and d–d intraband transitions in the metals. Four compounds, CuTaN 2 , CuNbN 2 , AgTaN 2 , and AgNbN 2 , are predicted to exhibit large light absorption in the range of 1.0 to 1.7 eV, therefore making these materials good candidates for solar-energy conversion applications. Two compounds, AuTaN 2 and AuNbN 2 , have band gaps and absorption onsets near the ideal range for obtaining high solar-cell conversion efficiency, suggesting that these compounds could become potential candidates as absorber materials in tandem solar cells or for band-gap engineering by alloying. 

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3. Electromechanical switching in DNA–CNT supramolecular structures

   https://doi.org/10.1063/5.0272693  

   Alolaiyan, Olaiyan; De, Arpan; Anantram, M P (July 2025, Applied Physics Letters)

   The characteristics of the interface between DNA and metallic carbon nanotube (CNT) in supramolecular assemblies are important to understand for electronic and sensing applications. We study the mechanical stability and electronic properties of these interfaces with amino and ester linkers using computational experiments. Our study demonstrates that both linkers significantly enhance the mechanical stability of DNA–CNT systems, with the DNA adopting a stable and lower energy perpendicular orientation relative to the CNT as opposed to a conventional parallel arrangement. This lower energy configuration is driven by nonbonded interactions between the DNA base and the CNT surface. Our calculations also reveal that interface resistance is primarily governed by DNA–CNT interactions with negligible contribution from the linkers. In the case of the amino linker, we predict a 100-fold transmission ratio between parallel and perpendicular configurations of DNA relative to CNT. This observation can be used to build an electromechanical switch with fast switching times (30 ns). The ester linker, on the contrary, enables a better electronic coupling between the DNA and CNT even when strained. 

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4. Pressure‐Induced Structural and Magnetic Evolution in Layered Antiferromagnet YbMn ₂ Sb ₂

   https://doi.org/10.1002/aelm.202500820  

   Xu, Mingyu; Boswell, Matt; Rutherford, Aya; Peng, Cheng; Zhou, Ying; Wang, Shuyang; Yang, Zhaorong; dos_Santos, Antonio M; Zhou, Haidong; Xie, Weiwei (April 2026, Advanced Electronic Materials)

   ABSTRACT Electronic states under pressure exhibit unconventional spin and charge dynamics that provide a powerful route to uncover exotic phases in quantum materials. Here, we present the structural, magnetic, and electronic evolution of YbMn₂Sb₂under pressure. Single‐crystal X‐ray diffraction reveals a pressure‐induced structural transition from the space group trigonalPm1 to the monoclinicP2₁/mphase near 3.5 GPa, which remains stable up to 10 GPa. Magnetization measurements display an anomalously weak net magnetic moment and the absence of Curie–Weiss behavior up to 400 K, suggesting the formation of short‐range Mn moment pairs that cancel macroscopically and subsequently evolve into long‐range order upon cooling. Temperature‐dependent resistivity shows semiconducting behavior with a transition at ∼119 K at ambient pressure, while pressure induces a dramatic suppression of resistance and the emergence of metallic‐like temperature dependence, stabilized beyond 5 GPa. This pressure‐driven semiconductor‐metal transition is consistent with our density functional theory calculations, confirming the closing of the band gap under compression. Neutron diffraction under pressure identifies an incommensurate magnetic structure with antiparallel correlations between paired spins. Together, these results demonstrate how pressure‐driven structural tuning and competing exchange interactions stabilize unconventional magnetic states in this low‐dimensional magnetic semiconductor. 

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5. Quantum critical phase of FeO spans conditions of Earth’s lower mantle

   https://doi.org/10.1038/s41467-024-47489-w  

   Ho, Wai-Ga D; Zhang, Peng; Haule, Kristjan; Jackson, Jennifer M; Dobrosavljević, Vladimir; Dobrosavljevic, Vasilije V (December 2024, Nature Communications)

   Abstract Seismic and mineralogical studies have suggested regions at Earth’s core-mantle boundary may be highly enriched in FeO, reported to exhibit metallic behavior at extreme pressure-temperature (P–T) conditions. However, underlying electronic processes in FeO remain poorly understood. Here we explore the electronic structure ofB1-FeO at extreme conditions with large-scale theoretical modeling using state-of-the-art embedded dynamical mean field theory (eDMFT). Fine sampling of the phase diagram reveals that, instead of sharp metallization, compression of FeO at high temperatures induces a gradual orbitally selective insulator-metal transition. Specifically, atP–Tconditions of the lower mantle, FeO exists in an intermediate quantum critical state, characteristic of strongly correlated electronic matter. Transport in this regime, distinct from insulating or metallic behavior, is marked by incoherent diffusion of electrons in the conductingt_2gorbital and a band gap in thee_gorbital, resulting in moderate electrical conductivity (~10⁵S/m) with modestP–Tdependence as observed in experiments. Enrichment of solid FeO can thus provide a unifying explanation for independent observations of low seismic velocities and elevated electrical conductivities in heterogeneities at Earth’s mantle base. 

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