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1. Time delays from one-photon transitions in the continuum

   https://doi.org/10.1364/OPTICA.378639  

   Fuchs, Jaco; Douguet, Nicolas; Donsa, Stefan; Martin, Fernando; Burgdörfer, Joachim; Argenti, Luca; Cattaneo, Laura; Keller, Ursula (February 2020, Optica)

   Attosecond photoionization time delays reveal information about the potential energy landscape that an outgoing electron wavepacket probes upon ionization. In this study, we experimentally quantify the dependence of the time delay on the angular momentum of the liberated photoelectrons. For this purpose, we resolved electron quantum-path interference spectra in energy and angle using a two-color attosecond pump–probe photoionization experiment in helium. A fitting procedure of the angle-dependent interference pattern allows us to disentangle the relative phase of all four quantum pathways that are known to contribute to the final photoelectron signal. In particular, we resolve the dependence on angular momentum of the delay of one-photon transitions between continuum states, which is an essential and universal contribution to the total photoionization delay observed in attosecond pump–probe measurements. For such continuum–continuum transitions, we measure a delay between outgoing $s$and $d$electrons as large as 12 attoseconds, close to the ionization threshold in helium. Both single-active-electron and first-principlesab initiosimulations confirm this observation for helium and hydrogen, demonstrating the universality of the observed delays. 

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2. Compact nonvolatile polarization switch using an asymmetric Sb ₂ Se ₃ -loaded silicon waveguide

   https://doi.org/10.1364/OE.482817  

   Jin, Huimin; Niu, Lei; Zheng, Jiajiu; Xu, Peipeng; Majumdar, Arka (January 2023, Optics Express)

   We propose and simulate a compact (∼29.5 µm-long) nonvolatile polarization switch based on an asymmetric Sb₂Se₃-clad silicon photonic waveguide. The polarization state is switched between TM₀and TE₀mode by modifying the phase of nonvolatile Sb₂Se₃between amorphous and crystalline. When the Sb₂Se₃is amorphous, two-mode interference happens in the polarization-rotation section resulting in efficient TE₀-TM₀conversion. On the other hand, when the material is in the crystalline state, there is little polarization conversion because the interference between the two hybridized modes is significantly suppressed, and both TE₀and TM₀modes go through the device without any change. The designed polarization switch has a high polarization extinction ratio of > 20 dB and an ultra-low excess loss of < 0.22 dB in the wavelength range of 1520-1585 nm for both TE₀and TM₀modes. 

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3. Electron hole asymmetry in the phase diagram of carrier-tuned CsV3Sb5

   https://doi.org/10.3389/femat.2023.1257490  

   Capa_Salinas, Andrea N; Ortiz, Brenden R; Bales, Calvin; Frassineti, Jonathan; Mitrović, Vesna F; Wilson, Stephen D (October 2023, Frontiers in Electronic Materials)

   In this work, we study the effect of electron doping on the kagome superconductor CsV₃Sb₅. Single crystals and powders of CsV₃Sb_5−xTe_xare synthesized and characterized via magnetic susceptibility, nuclear quadrupole resonance, and x-ray diffraction measurements, where we observe a slight suppression of the charge density wave transition temperature and superconducting temperature with the introduction of electron dopants. In contrast to hole doping, both transitions survive relatively unperturbed up to the solubility limit of Te within the lattice. A comparison is presented between the electronic phase diagrams of electron- and hole-tuned CsV₃Sb₅. 

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4. Incommensurate charge-stripe correlations in the kagome superconductor CsV3Sb5−xSnx

   https://doi.org/10.1038/s41535-023-00570-x  

   Kautzsch, Linus; Oey, Yuzki M.; Li, Hong; Ren, Zheng; Ortiz, Brenden R.; Pokharel, Ganesh; Seshadri, Ram; Ruff, Jacob; Kongruengkit, Terawit; Harter, John W.; et al (July 2023, npj Quantum Materials)

   Abstract The class ofAV₃Sb₅(A=K, Rb, Cs) kagome metals hosts unconventional charge density wave states seemingly intertwined with their low temperature superconducting phases. The nature of the coupling between these two states and the potential presence of nearby, competing charge instabilities however remain open questions. This phenomenology is strikingly highlighted by the formation of two ‘domes’ in the superconducting transition temperature upon hole-doping CsV₃Sb₅. Here we track the evolution of charge correlations upon the suppression of long-range charge density wave order in the first dome and into the second of the hole-doped kagome superconductor CsV₃Sb_5−xSn_x. Initially, hole-doping drives interlayer charge correlations to become short-ranged with their periodicity diminished along the interlayer direction. Beyond the peak of the first superconducting dome, the parent charge density wave state vanishes and incommensurate, quasi-1D charge correlations are stabilized in its place. These competing, unidirectional charge correlations demonstrate an inherent electronic rotational symmetry breaking in CsV₃Sb₅, and reveal a complex landscape of charge correlations within its electronic phase diagram. Our data suggest an inherent 2k_fcharge instability and competing charge orders in theAV₃Sb₅class of kagome superconductors. 

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5. Near-optimal Smooth Path Planning for Multisection Continuum Arms

   https://doi.org/10.1109/ROBOSOFT.2019.8722778  

   Deng, Jiahao; Meng, Brandon H.; Kanj, Iyad; Godage, Isuru S. (April 2019, 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft))

   We study the path planning problem for continuum-arm robots, in which we are given a starting and an end point, and we need to compute a path for the tip of the continuum arm between the two points. We consider both cases where obstacles are present and where they are not. We demonstrate how to leverage the continuum arm features to introduce a new model that enables a path planning approach based on the configurations graph, for a continuum arm consisting of three sections, each consisting of three muscle actuators. The algorithm we apply to the configurations graph allows us to exploit parallelism in the computation to obtain efficient implementation. We conducted extensive tests, and the obtained results show the completeness of the proposed algorithm under the considered discretizations, in both cases where obstacles are present and where they are not. We compared our approach to the standard inverse kinematics approach. While the inverse kinematics approach is much faster when successful, our algorithm always succeeds in finding a path or reporting that no path exists, compared to a roughly 70% success rate of the inverse kinematics approach (when a path exists). 

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