SIMES Publications
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"Ultralight and fire-extinguishing current collectors for high-energy and high-safety lithium-ion batteries" — Yusheng Ye: Lien-Yang Chou, Yayuan Liu, Hansen Wang, Hiang Kwee Lee, Wenxiao Huang, Jiayu Wan, Kai Liu, Guangmin Zhou, Yufei Yang, Ankun Yang, Xin Xiao, Xin Gao, David Thomas Boyle, Hao Chen, Wenbo Zhang, Sang Cheol Kim & Yi Cui ; Nature Energy, 10/15/20.
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Lien-Yang Chou, Yayuan Liu, Hansen Wang, Hiang Kwee Lee, Wenxiao Huang, Jiayu Wan, Kai Liu, Guangmin Zhou, Yufei Yang, Ankun Yang, Xin Xiao, Xin Gao, David Thomas Boyle, Hao Chen, Wenbo Zhang, Sang Cheol Kim & Yi Cui
Abstract
Inactive components and safety hazards are two critical challenges in realizing high-energy lithium-ion batteries. Metal foil current collectors with high density are typically an integrated part of lithium-ion batteries yet deliver no capacity. Meanwhile, high-energy batteries can entail increased fire safety issues. Here we report a composite current collector design that simultaneously minimizes the ‘dead weight’ within the cell and improves fire safety. An ultralight polyimide-based current collector (9 μm thick, specific mass 1.54 mg cm−2) is prepared by sandwiching a polyimide embedded with triphenyl phosphate flame retardant between two superthin Cu layers (~500 nm). Compared to lithium-ion batteries assembled with the thinnest commercial metal foil current collectors (~6 µm), batteries equipped with our composite current collectors can realize a 16–26% improvement in specific energy and rapidly self-extinguish fires under extreme conditions such as short circuits and thermal runaway.
"Quantum-well states in fractured crystals of the heavy-fermion material CeCoIn5" — Nicolas Gauthier: Jonathan A. Sobota, Makoto Hashimoto, Heike Pfau, Dong-Hui Lu, Eric D. Bauer, Filip Ronning, Patrick S. Kirchmann, and Zhi-Xun Shen; Physical Review B, 09/08/20.
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Jonathan A. Sobota, Makoto Hashimoto, Heike Pfau, Dong-Hui Lu, Eric D. Bauer, Filip Ronning, Patrick S. Kirchmann, and Zhi-Xun Shen
Abstract
Quantum-well states appear in metallic thin films due to the confinement of the wave function by the film interfaces. Using angle-resolved photoemission spectroscopy, we unexpectedly observe quantum-well states in fractured single crystals of CeCoIn5. We confirm that confinement occurs by showing that these states’ binding energies are photon-energy independent and are well described with a phase accumulation model, commonly applied to quantum-well states in thin films. This indicates that atomically flat thin films can be formed by fracturing hard single crystals. For the two samples studied, our observations are explained by free-standing flakes with thicknesses of 206 and 101 Å. We extend our analysis to extract bulk properties of CeCoIn5. Specifically, we obtain the dispersion of a three-dimensional band near the zone center along in-plane and out-of-plane momenta. We establish part of its Fermi surface, which corresponds to a hole pocket centered at Γ. We also reveal a change of its dispersion with temperature, a signature that may be caused by the Kondo hybridization.
"Tuning time and energy resolution in time-resolved photoemission spectroscopy with nonlinear crystals" — Alexandre Gauthier: Jonathan A. Sobota, Nicolas Gauthier, Ke-Jun Xu, Heike Pfau, Costel R. Rotundu, Zhi-Xun Shen, and Patrick S. Kirchmann; Journal of Applied Physics, 09/01/20.
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Jonathan A. Sobota, Nicolas Gauthier, Ke-Jun Xu, Heike Pfau, Costel R. Rotundu, Zhi-Xun Shen, and Patrick S. Kirchmann
Abstract
Time- and angle-resolved photoemission spectroscopy is a powerful probe of electronic band structures out of equilibrium. Tuning time and energy resolution to suit a particular scientific question has become an increasingly important experimental consideration. Many instruments use cascaded frequency doubling in nonlinear crystals to generate the required ultraviolet probe pulses. We demonstrate how calculations clarify the relationship between laser bandwidth and nonlinear crystal thickness contributing to experimental resolutions and place intrinsic limits on the achievable time-bandwidth product. Experimentally, we tune time and energy resolution by varying the thickness of nonlinear β-BaB2O4 crystals for frequency upconversion, providing a flexible experiment design. We achieve time resolutions of 58–103 fs and corresponding energy resolutions of 55–27 meV. We propose a method to select crystal thickness based on desired experimental resolutions.
"Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate" — W. S. Lee: Ke-Jin J. Zhou, M. Hepting, J. Li, A. Nag, A. C. Walters, M. Garcia-Fernandez, H. C. Robarts, M. Hashimoto, H. Lu, B. Nosarzewski, D. Song, H. Eisaki, Z. X. Shen, B. Moritz, J. Zaanen & T. P. Devereaux; Nature Physics, 08/31/20.
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Ke-Jin J. Zhou, M. Hepting, J. Li, A. Nag, A. C. Walters, M. Garcia-Fernandez, H. C. Robarts, M. Hashimoto, H. Lu, B. Nosarzewski, D. Song, H. Eisaki, Z. X. Shen, B. Moritz, J. Zaanen & T. P. Devereaux
Abstract
Copper oxide high-TC superconductors possess a number of exotic orders that coexist with or are proximal to superconductivity. Quantum fluctuations associated with these orders may account for the unusual characteristics of the normal state, and possibly affect the superconductivity1,2,3,4. Yet, spectroscopic evidence for such quantum fluctuations remains elusive. Here, we use resonant inelastic X-ray scattering to reveal spectroscopic evidence of fluctuations associated with a charge order5,6,7,8,9,10,11,12,13,14 in nearly optimally doped Bi2Sr2CaCu2O8+δ. In the superconducting state, while the quasielastic charge order signal decreases with temperature, the interplay between charge order fluctuations and bond-stretching phonons in the form of a Fano-like interference increases, an observation that is incompatible with expectations for competing orders. Invoking general principles, we argue that this behaviour reflects the properties of a dissipative system near an order–disorder quantum critical point, where the dissipation varies with the opening of the pseudogap and superconducting gap at low temperatures, leading to the proliferation of quantum critical fluctuations, which melt charge order.
"High-harmonic generation in spin-orbit coupled systems" — Markus Lysne: Yuta Murakami, Michael Schüler, and Philipp Werner; Physical Review B, 08/26/20.
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Yuta Murakami, Michael Schüler, and Philipp Werner
Abstract
We study high-harmonic generation in two-dimensional electron systems with Rashba and Dresselhaus spin-orbit coupling and derive harmonic generation selection rules with the help of group theory. Based on the band structures of these minimal models and explicit simulations we reveal how the spin-orbit parameters control the cutoff energy in the high-harmonic spectrum. We also show that the magnetic field and polarization dependence of this spectrum provides information on the magnitude of the Rashba and Dresselhaus spin-orbit coupling parameters. The shape of the Fermi surface can be deduced at least qualitatively and if only one type of spin-orbit coupling is present, the coupling strength can be determined.
"Anomalous Hall and Nernst effects in epitaxial films of topological kagome magnet Fe3Sn2" — Durga Khadka: T. R. Thapaliya, Sebastian Hurtado Parra, Jiajia Wen, Ryan Need, James M. Kikkawa, and S. X. Huang; Physical Review Materials, 08/21/20.
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T. R. Thapaliya, Sebastian Hurtado Parra, Jiajia Wen, Ryan Need, James M. Kikkawa, and S. X. Huang
Abstract
The topological kagome magnet (TKM) Fe3Sn2 exhibits unusual topological properties, flat electronic bands, and chiral spin textures, making it an exquisite materials platform to explore the interplay between topological band structure, strong electron correlations, and magnetism. Here we report the synthesis of high-quality epitaxial (0001) Fe3Sn2 films with large intrinsic anomalous Hall effect close to that measured in bulk single crystals. In addition, we measured a large, anisotropic anomalous Nernst coefficient Syx of 1.26μVK−1, roughly 2–5 times greater than that of common ferromagnets, suggesting the presence of Berry curvature sources near the Fermi level in this system. Crucially, the realization of high-quality Fe3Sn2 films opens the door to explore emergent interfacial physics and create novel spintronic devices based on TKMs by interfacing Fe3Sn2 with other quantum materials and by nanostructure patterning.
"Frequency-dependent sensitivity of AC elastocaloric effect measurements explored through analytical and numerical models" — J. A. W. Straquadine: M. S. Ikeda, and I. R. Fisher; Review of Scientific Instruments, 08/11/20.
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M. S. Ikeda, and I. R. Fisher
Abstract
We present a comprehensive study of the frequency-dependent sensitivity for measurements of the AC elastocaloric effect by applying both exactly soluble models and numerical methods to the oscillating heat flow problem. These models reproduce the finer details of the thermal transfer functions observed in experiments, considering here representative data for single-crystal Ba(Fe1−xCox)2As2. Based on our results, we propose a set of practical guidelines for experimentalists using this technique. This work establishes a baseline against which the frequency response of the AC elastocaloric technique can be compared and provides intuitive explanations of the detailed structure observed in experiments.
"Test of the Dynamic-Domain and Critical Scattering Hypotheses in Cubic Methylammonium Lead Triiodide" — Nicholas J. Weadock: Peter M. Gehring , Aryeh Gold-Parker, Ian C. Smith, Hemamala I. Karunadasa, and Michael F. Toney; Physical Review Letters, 08/10/20.
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Peter M. Gehring , Aryeh Gold-Parker, Ian C. Smith, Hemamala I. Karunadasa, and Michael F. Toney
Abstract
We investigate the hypothesis of dynamic tetragonal domains occurring in cubic CH3NH3PbI3using high-resolution neutron spectroscopy to study a fully deuterated single crystal. The R-point scattering above the 327.5 K cubic-tetragonal phase transition is always resolution limited in energy and therefore inconsistent with dynamic-domain predictions. This behavior is instead consistent with the central peak phenomenon observed in other perovskites. The scattering may originate from small, static, tetragonal-phase domains nucleating about crystal defects, and the temperature dependence demonstrates the transition is first order.
"Magnetic breakdown and charge density wave formation: A quantum oscillation study of the rare-earth tritellurides" — P. Walmsley: S. Aeschlimann, J. A. W. Straquadine, P. Giraldo-Gallo, S. C. Riggs, M. K. Chan, R. D. McDonald, and I. R. Fisher; Physical Review B, 07/30/20.
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S. Aeschlimann, J. A. W. Straquadine, P. Giraldo-Gallo, S. C. Riggs, M. K. Chan, R. D. McDonald, and I. R. Fisher
Abstract
The rare-earth tritellurides (RTe3, where R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y) form a charge density wave state consisting of a single unidirectional charge density wave for lighter R, with a second unidirectional charge density wave, perpendicular and in addition to the first, also present at low temperatures for heavier R. We present a quantum oscillation study in magnetic fields up to 65 T that compares the single charge density wave state with the double charge density wave state both above and below the magnetic breakdown field of the second charge density wave. In the double charge density wave state it is observed that there remain several small, light pockets, with the largest occupying around 0.5% of the Brillouin zone. By applying magnetic fields above the independently determined magnetic breakown field, the quantum oscillation frequencies of the single charge density wave state are recovered, as expected in a magnetic breakdown scenario. Measurements of the electronic effective mass do not show any divergence or significant increase on the pockets of Fermi surface observed here as the putative quantum phase transition between the single and the double charge density wave states is approached.
"Opportunities for Cryogenic Electron Microscopy in Materials Science and Nanoscience" — Yanbin Li,: William Huang, Yuzhang Li, Wah Chiu, and Yi Cui; ACS Nano, 07/28/20.
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William Huang, Yuzhang Li, Wah Chiu, and Yi Cui
Abstract
Cryogenic electron microscopy (cryo-EM) was the basis for the 2017 Nobel Prize in Chemistry for its profound impact on the field of structural biology by freezing and stabilizing fragile biomolecules for near atomic-resolution imaging in their native states. Beyond life science, the development of cryo-EM for the physical sciences may offer access to previously inaccessible length scales for materials characterization in systems that would otherwise be too sensitive for high-resolution electron microscopy and spectroscopy. Weakly bonded and reactive materials that typically degrade under electron irradiation and environmental exposure can potentially be stabilized by cryo-EM, opening up exciting opportunities to address many central questions in materials science. New discoveries and fundamental breakthroughs in understanding are likely to follow. In this Perspective, we identify six major areas in materials science that may benefit from the interdisciplinary application of cryo-EM: (1) batteries, (2) soft polymers, (3) metal−organic frameworks, (4) perovskite solar cells, (5) electrocatalysts, and (6) quantum materials. We highlight long-standing questions in each of these areas that cryo-EM can potentially address, which would firmly establish the powerful tool’s broad scope and utility beyond biology.
