@article{10177, abstract = {Phonon polaritons (PhPs)—light coupled to lattice vibrations—with in-plane hyperbolic dispersion exhibit ray-like propagation with large wave vectors and enhanced density of optical states along certain directions on a surface. As such, they have raised a surge of interest, promising unprecedented manipulation of infrared light at the nanoscale in a planar circuitry. Here, we demonstrate focusing of in-plane hyperbolic PhPs propagating along thin slabs of α-MoO3. To that end, we developed metallic nanoantennas of convex geometries for both efficient launching and focusing of the polaritons. The foci obtained exhibit enhanced near-field confinement and absorption compared to foci produced by in-plane isotropic PhPs. Foci sizes as small as λp/4.5 = λ0/50 were achieved (λp is the polariton wavelength and λ0 is the photon wavelength). Focusing of in-plane hyperbolic polaritons introduces a first and most basic building block developing planar polariton optics using in-plane anisotropic van der Waals materials.}, author = {Martín-Sánchez, Javier and Duan, Jiahua and Taboada-Gutiérrez, Javier and Álvarez-Pérez, Gonzalo and Voronin, Kirill V. and Prieto Gonzalez, Ivan and Ma, Weiliang and Bao, Qiaoliang and Volkov, Valentyn S. and Hillenbrand, Rainer and Nikitin, Alexey Y. and Alonso-González, Pablo}, issn = {2375-2548}, journal = {Science Advances}, number = {41}, publisher = {American Association for the Advancement of Science}, title = {{Focusing of in-plane hyperbolic polaritons in van der Waals crystals with tailored infrared nanoantennas}}, doi = {10.1126/sciadv.abj0127}, volume = {7}, year = {2021}, } @article{9334, abstract = {Polaritons with directional in-plane propagation and ultralow losses in van der Waals (vdW) crystals promise unprecedented manipulation of light at the nanoscale. However, these polaritons present a crucial limitation: their directional propagation is intrinsically determined by the crystal structure of the host material, imposing forbidden directions of propagation. Here, we demonstrate that directional polaritons (in-plane hyperbolic phonon polaritons) in a vdW crystal (α-phase molybdenum trioxide) can be directed along forbidden directions by inducing an optical topological transition, which emerges when the slab is placed on a substrate with a given negative permittivity (4H–silicon carbide). By visualizing the transition in real space, we observe exotic polaritonic states between mutually orthogonal hyperbolic regimes, which unveil the topological origin of the transition: a gap opening in the dispersion. This work provides insights into optical topological transitions in vdW crystals, which introduce a route to direct light at the nanoscale.}, author = {Duan, J. and Álvarez-Pérez, G. and Voronin, K. V. and Prieto Gonzalez, Ivan and Taboada-Gutiérrez, J. and Volkov, V. S. and Martín-Sánchez, J. and Nikitin, A. Y. and Alonso-González, P.}, issn = {2375-2548}, journal = {Science Advances}, number = {14}, publisher = {AAAS}, title = {{Enabling propagation of anisotropic polaritons along forbidden directions via a topological transition}}, doi = {10.1126/sciadv.abf2690}, volume = {7}, year = {2021}, } @article{19812, abstract = {A nearly free electron metal and a Mott insulating state can be thought of as opposite ends of the spectrum of possibilities for the motion of electrons in a solid. Understanding their interaction lies at the heart of the correlated electron problem. In the magnetic oxide metal PdCrO2, nearly free and Mott-localized electrons exist in alternating layers, forming natural heterostructures. Using angle-resolved photoemission spectroscopy, quantitatively supported by a strong coupling analysis, we show that the coupling between these layers leads to an “intertwined” excitation that is a convolution of the charge spectrum of the metallic layer and the spin susceptibility of the Mott layer. Our findings establish PdCrO2 as a model system in which to probe Kondo lattice physics and also open new routes to use the a priori nonmagnetic probe of photoemission to gain insights into the spin susceptibility of correlated electron materials.}, author = {Sunko, Veronika and Mazzola, F. and Kitamura, S. and Khim, S. and Kushwaha, P. and Clark, O. J. and Watson, M. D. and Marković, I. and Biswas, D. and Pourovskii, L. and Kim, T. K. and Lee, T.-L. and Thakur, P. K. and Rosner, H. and Georges, A. and Moessner, R. and Oka, T. and Mackenzie, A. P. and King, P. D. C.}, issn = {2375-2548}, journal = {Science Advances}, number = {6}, publisher = {American Association for the Advancement of Science}, title = {{Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system}}, doi = {10.1126/sciadv.aaz0611}, volume = {6}, year = {2020}, } @article{15057, abstract = {Vaccinia virus–related kinase (VRK) is an evolutionarily conserved nuclear protein kinase. VRK-1, the single Caenorhabditis elegans VRK ortholog, functions in cell division and germline proliferation. However, the role of VRK-1 in postmitotic cells and adult life span remains unknown. Here, we show that VRK-1 increases organismal longevity by activating the cellular energy sensor, AMP-activated protein kinase (AMPK), via direct phosphorylation. We found that overexpression of vrk-1 in the soma of adult C. elegans increased life span and, conversely, inhibition of vrk-1 decreased life span. In addition, vrk-1 was required for longevity conferred by mutations that inhibit C. elegans mitochondrial respiration, which requires AMPK. VRK-1 directly phosphorylated and up-regulated AMPK in both C. elegans and cultured human cells. Thus, our data show that the somatic nuclear kinase, VRK-1, promotes longevity through AMPK activation, and this function appears to be conserved between C. elegans and humans.}, author = {Park, Sangsoon and Artan, Murat and Han, Seung Hyun and Park, Hae-Eun H. and Jung, Yoonji and Hwang, Ara B. and Shin, Won Sik and Kim, Kyong-Tai and Lee, Seung-Jae V.}, issn = {2375-2548}, journal = {Science Advances}, number = {27}, publisher = {American Association for the Advancement of Science}, title = {{VRK-1 extends life span by activation of AMPK via phosphorylation}}, doi = {10.1126/sciadv.aaw7824}, volume = {6}, year = {2020}, } @article{7910, abstract = {Quantum illumination uses entangled signal-idler photon pairs to boost the detection efficiency of low-reflectivity objects in environments with bright thermal noise. Its advantage is particularly evident at low signal powers, a promising feature for applications such as noninvasive biomedical scanning or low-power short-range radar. Here, we experimentally investigate the concept of quantum illumination at microwave frequencies. We generate entangled fields to illuminate a room-temperature object at a distance of 1 m in a free-space detection setup. We implement a digital phase-conjugate receiver based on linear quadrature measurements that outperforms a symmetric classical noise radar in the same conditions, despite the entanglement-breaking signal path. Starting from experimental data, we also simulate the case of perfect idler photon number detection, which results in a quantum advantage compared with the relative classical benchmark. Our results highlight the opportunities and challenges in the way toward a first room-temperature application of microwave quantum circuits.}, author = {Barzanjeh, Shabir and Pirandola, S. and Vitali, D and Fink, Johannes M}, issn = {2375-2548}, journal = {Science Advances}, number = {19}, publisher = {AAAS}, title = {{Microwave quantum illumination using a digital receiver}}, doi = {10.1126/sciadv.abb0451}, volume = {6}, year = {2020}, } @article{8986, abstract = {Flowering plants display the highest diversity among plant species and have notably shaped terrestrial landscapes. Nonetheless, the evolutionary origin of their unprecedented morphological complexity remains largely an enigma. Here, we show that the coevolution of cis-regulatory and coding regions of PIN-FORMED (PIN) auxin transporters confined their expression to certain cell types and directed their subcellular localization to particular cell sides, which together enabled dynamic auxin gradients across tissues critical to the complex architecture of flowering plants. Extensive intraspecies and interspecies genetic complementation experiments with PINs from green alga up to flowering plant lineages showed that PIN genes underwent three subsequent, critical evolutionary innovations and thus acquired a triple function to regulate the development of three essential components of the flowering plant Arabidopsis: shoot/root, inflorescence, and floral organ. Our work highlights the critical role of functional innovations within the PIN gene family as essential prerequisites for the origin of flowering plants.}, author = {Zhang, Yuzhou and Rodriguez Solovey, Lesia and Li, Lanxin and Zhang, Xixi and Friml, Jiří}, issn = {2375-2548}, journal = {Science Advances}, number = {50}, publisher = {AAAS}, title = {{Functional innovations of PIN auxin transporters mark crucial evolutionary transitions during rise of flowering plants}}, doi = {10.1126/sciadv.abc8895}, volume = {6}, year = {2020}, } @article{6919, author = {Qi, Chao and Minin, Giulio Di and Vercellino, Irene and Wutz, Anton and Korkhov, Volodymyr M.}, issn = {2375-2548}, journal = {Science Advances}, number = {9}, publisher = {American Association for the Advancement of Science}, title = {{Structural basis of sterol recognition by human hedgehog receptor PTCH1}}, doi = {10.1126/sciadv.aaw6490}, volume = {5}, year = {2019}, } @article{17949, abstract = {Single-molecule electronic devices provide researchers with an unprecedented ability to relate novel physical phenomena to molecular chemical structures. Typically, conjugated aromatic molecular backbones are relied upon to create electronic devices, where the aromaticity of the building blocks is used to enhance conductivity. We capitalize on the classical physical organic chemistry concept of Hückel antiaromaticity by demonstrating a single-molecule switch that exhibits low conductance in the neutral state and, upon electrochemical oxidation, reversibly switches to an antiaromatic high-conducting structure. We form single-molecule devices using the scanning tunneling microscope–based break-junction technique and observe an on/off ratio of ~70 for a thiophenylidene derivative that switches to an antiaromatic state with 6-4-6-π electrons. Through supporting nuclear magnetic resonance measurements, we show that the doubly oxidized core has antiaromatic character and we use density functional theory calculations to rationalize the origin of the high-conductance state for the oxidized single-molecule junction. Together, our work demonstrates how the concept of antiaromaticity can be exploited to create single-molecule devices that are highly conducting.}, author = {Yin, Xiaodong and Zang, Yaping and Zhu, Liangliang and Low, Jonathan Z. and Liu, Zhen-Fei and Cui, Jing and Neaton, Jeffrey B. and Venkataraman, Latha and Campos, Luis M.}, issn = {2375-2548}, journal = {Science Advances}, number = {10}, publisher = {American Association for the Advancement of Science}, title = {{A reversible single-molecule switch based on activated antiaromaticity}}, doi = {10.1126/sciadv.aao2615}, volume = {3}, year = {2017}, } @article{849, abstract = {Understanding the principles that led to the current complexity of the genetic code is a central question in evolution. Expansion of the genetic code required the selection of new transfer RNAs (tRNAs) with specific recognition signals that allowed them to be matured, modified, aminoacylated, and processed by the ribosome without compromising the fidelity or efficiency of protein synthesis. We show that saturation of recognition signals blocks the emergence of new tRNA identities and that the rate of nucleotide substitutions in tRNAs is higher in species with fewer tRNA genes. We propose that the growth of the genetic code stalled because a limit was reached in the number of identity elements that can be effectively used in the tRNA structure.}, author = {Saint Léger, Adélaïde and Bello, Carla and Dans, Pablo and Torres, Adrian and Novoa, Eva and Camacho, Noelia and Orozco, Modesto and Kondrashov, Fyodor and Ribas De Pouplana, Lluís}, issn = {2375-2548}, journal = {Science advances}, number = {4}, publisher = {American Association for the Advancement of Science}, title = {{Saturation of recognition elements blocks evolution of new tRNA identities}}, doi = {10.1126/sciadv.1501860}, volume = {2}, year = {2016}, }