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1. Measurement of the dynamic charge susceptibility near the charge density wave transition in ErTe3

   Chaudhuri, Dipanjan; Jiang, Qianni; Guo, Xuefei; Chen, Ji; Kengle, Caitlin S; Hoveyda-Marashi, Farzaneh; Bernal-Choban, Camille; de_Vries, Niels; Chiang, Tai C; Fradkin, Eduardo; et al (December 2024, 2411.14746)

   A charge density wave (CDW) is a phase of matter characterized by a periodic modulation of the valence electron density accompanied by a distortion of the lattice structure. The microscopic details of CDW formation are closely tied to the dynamic charge susceptibility, χ(q, ω), which describes the behavior of electronic collective modes. Despite decades of extensive study, the behavior of χ(q, ω) in the vicinity of a CDWtransition has never been measured with high energy resolution (∼meV). Here, we investigate the canonical CDW transition in ErTe3 using momentum-resolved electron energy loss spectroscopy (M-EELS), a technique uniquely sensitive to valence band charge excitations. Unlike phonons in these materials, which undergo conventional softening due to the Kohn anomaly at the CDW wavevector, the electronic excitations display purely relaxational dynamics that are well described by a diffusive model. The diffusivity peaks around 250 K, just below the critical temperature. Additionally, we report, for the first time, a divergence in the real part of χ(q, ω) in the static limit (ω → 0), a phenomenon predicted to characterize CDWs since the 1970s. These results highlight the importance of energy- and momentum-resolved measurements of electronic susceptibility and demonstrate the power of M-EELS as a versatile probe of charge dynamics in materials. 

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2. Dipole Charge Detection: Toward the Readout of Bistable Charge States in Molecular QCA

   https://doi.org/10.1109/LSENS.2023.3322265  

   Rahaman, Mohammad Istiaque; Szakmany, Gergo P; Orlov, Alexei O; Snider, Gregory L (January 2024, IEEE Sensors Letters)
3. Effects of charge fluctuation and charge regulation on the phase transitions in stoichiometric VO2

   https://doi.org/10.1038/s41598-020-73447-9  

   Joshi, Siddharth; Smieszek, Nicholas; Chakrapani, Vidhya (October 2020, Scientific Reports)

   Abstract Detailed electrical and photoemission studies were carried out to probe the chemical nature of the insulating ground state of VO₂, whose properties have been an issue for accurate prediction by common theoretical probes. The effects of a systematic modulation of oxygen over-stoichiometry of VO₂from 1.86 to 2.44 on the band structure and insulator–metal transitions are presented for the first time. Results offer a different perspective on the temperature- and doping-induced IMT process. They suggest that charge fluctuation in the metallic phase of intrinsic VO₂results in the formation of e⁻and h⁺pairs that lead to delocalized polaronic V³⁺and V⁵⁺cation states. The metal-to-insulator transition is linked to the cooperative effects of changes in the V–O bond length, localization of V³⁺electrons at V⁵⁺sites, which results in the formation of V⁴⁺–V⁴⁺dimers, and removal of$$\pi^{*}$$ ${\pi }^{\ast }$screening electrons. It is shown that the nature of phase transitions is linked to the lattice V³⁺/V⁵⁺concentrations of stoichiometric VO₂and that electronic transitions are regulated by the interplay between charge fluctuation, charge redistribution, and structural transition. 

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4. Spin-Charge-Lattice Coupling across the Charge Density Wave Transition in a Kagome Lattice Antiferromagnet

   https://doi.org/10.1103/PhysRevLett.133.046502  

   Teng, Xiaokun; Tam, David_W; Chen, Lebing; Tan, Hengxin; Xie, Yaofeng; Gao, Bin; Granroth, Garrett_E; Ivanov, Alexandre; Bourges, Philippe; Yan, Binghai; et al (July 2024, Physical Review Letters)
5. Controlling the surface charge of simple viruses

   https://doi.org/10.1371/journal.pone.0255820  

   Duran-Meza, A. L.; Villagrana-Escareño, M. V.; Ruiz-García, J.; Knobler, C. M.; Gelbart, W. M. (September 2021, PLOS ONE)

   Rao, A. L. (Ed.)

   The vast majority of plant viruses are unenveloped, i . e ., they lack a lipid bilayer that is characteristic of most animal viruses. The interactions between plant viruses, and between viruses and surfaces, properties that are essential for understanding their infectivity and to their use as bionanomaterials, are largely controlled by their surface charge, which depends on pH and ionic strength. They may also depend on the charge of their contents, i.e., of their genes or–in the instance of virus-like particles–encapsidated cargo such as nucleic acid molecules, nanoparticles or drugs. In the case of enveloped viruses, the surface charge of the capsid is equally important for controlling its interaction with the lipid bilayer that it acquires and loses upon leaving and entering host cells. We have previously investigated the charge on the unenveloped plant virus Cowpea Chlorotic Mottle Virus (CCMV) by measurements of its electrophoretic mobility. Here we examine the electrophoretic properties of a structurally and genetically closely related bromovirus, Brome Mosaic Virus (BMV), of its capsid protein, and of its empty viral shells, as functions of pH and ionic strength, and compare them with those of CCMV. From measurements of both solution and gel electrophoretic mobilities (EMs) we find that the isoelectric point (pI) of BMV (5.2) is significantly higher than that of CCMV (3.7), that virion EMs are essentially the same as those of the corresponding empty capsids, and that the same is true for the pIs of the virions and of their cleaved protein subunits. We discuss these results in terms of current theories of charged colloidal particles and relate them to biological processes and the role of surface charge in the design of new classes of drug and gene delivery systems. 

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