Materials Science
Operando spectro-ptychography reveals dynamical charge-storage and degradation pathways in redox-active electrodes
Xiao Zhao, Yuchen Cao, Evan Z Carlson et al. (+13 more)
Electrochemical reactions at buried electrode-electrolyte interfaces govern how redox-active materials store and release energy. However, these reactions are difficult to visualize because chemical and morphological changes occur simultaneously over distinct length and time scales. Existing operando microscopies often require trade-offs among chemical sensitivity, spatial resolution and temporal resolution. Direct nanoscale tracking of such processes throughout extended timescale has therefore remained out of reach. Here, we develop a fast and robust operando soft X-ray spectro-ptychography platform that delivers chemical-state-resolved spatiotemporal movies of redox-active electrodes over the full battery lifetime. Applied to an alkaline Fe anode, the method reveals that reversible charge storage gives way to degradation through two competing processes: rapid hydroxide insertion that drives early reversible cycling, and slower dissolution-redeposition that redistributes Fe, enlarges FeOOH particles, and ultimately causes capacity loss. By separating fast charge-storage chemistry from slower degradation chemistry in operando and at both single-particle and particle ensemble level, this work establishes spectro-ptychography as a general approach for studying dynamic redox transformations in batteries, electrocatalysts, and other electrochemical materials.
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All authors Xiao Zhao, Yuchen Cao, Evan Z Carlson, Angel Burgos, Daniel Jacobs, Hanfeng Zhong, Lily Taylor, Haozhi Sha, Feng-yang Chen, Yu Shan, Hendrik Ohldag, Alexander Ditter, José A. Rodriguez, David Shapiro, William Chueh, Jianwei Miao
Materials Science · Cross-listed from physics.chem-ph
Polyatomic Thermal Radiative Dissociation in Microcavities
Enes Suyabatmaz, Tuan Nguyen and Raphael F. Ribeiro
Blackbody infrared radiative dissociation (BIRD) activates molecules through successive absorption of ambient thermal
photons until the internal energy reaches a dissociation threshold. Because these radiative transition rates depend on the electromagnetic density of states (DOS), structured infrared environments provide a route to control thermal unimolecular dissociation. Here we develop a state-resolved master-equation framework for polyatomic BIRD in a planar Au/MgO multilayer cavity, where the reactive cluster $\mathrm{(H_2O)_2Cl^-}$ is studied. The cavity modifies the kinetics through the DOS sampled by anharmonic fundamental, overtone, and combination transitions. We show that MgO surface
phonon polaritons produce strong near-field enhancements in the central
vacuum reaction region of a microcavity. We find that short cavities with thick polar
crystal layers yield the largest BIRD enhancements due to enhanced evanescent surface
phonon polariton contributions. We further include collisions with a methane bath gas and show that cavity DOS engineering shifts the crossover between BIRD and collisional activation. These results establish Reststrahlen-band DOS engineering as a practical strategy for controlling polyatomic BIRD in infrared microcavities.
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Materials Science
Mechanism of Band Gap Formation in Beam Networks
Kwangmin Lee, Charles Emmett Maher, Katherine A. Newhall et al. (+1 more)
Band gaps are commonly attributed to Bragg scattering or local resonance, yet it remains unclear whether these mechanisms govern band gap formation in beam networks. In this work, we explain band gap formation in beam networks in terms of a new mechanism, geometry-induced coupling between deformation modes. Specifically, band gap onset arises from axial-bending coupling at
lattice nodes and scales with the axial cutoff frequency of a one-dimensional periodic beam, whereas band gap termination is primarily governed by high-frequency rotational branches associated with beam geometry. This mechanism holds for both periodic and disordered beam networks. In periodic
lattices, it manifests through beam orientations at
lattice nodes, whereas in disordered networks it manifests through short-beam statistics arising from variations in beam length. Together, these results establish a unified mechanism for band gap formation across both periodic and disordered beam networks, providing new insight into the physical origin of band gaps in beam-network materials.
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All authors Kwangmin Lee, Charles Emmett Maher, Katherine A. Newhall, Ryan C. Hurley
Materials Science · Cross-listed from cond-mat.str-el
THz-induced phonon mode mixing and collective dynamics in a polar nanolattice
Elizabeth Skoropata, Peter M. Derlet, Hiroki Ueda et al. (+13 more)
Manipulating
phonons through
symmetry is a fundamental approach to alter the dynamic responses of materials. Most often new phases are sought through control of the unit-
cell (e.g. via strain, doping, light, etc.). By comparison, there is vast potential to look beyond the unit-
cell into higher-order architectures to control wave scattering and interference effects that remains less explored. We describe the THz-induced dynamics of an SrTiO$_{3}$ thin film with a nanoscale ordered interfacial dislocation network probed with 2- and 3-dimensional time-resolved x-ray diffraction and classical molecular dynamics simulations. We find that
symmetry breaking at all scales is an effective approach to create a dynamical electric polarization and to control
phonon mixing that generates previously unreported collective modes in the THz regime with circular
vortex-like displacements. This work opens a new pathway to explore dynamical functional properties that can be extended to
magnetic, electric, and ferroelectric systems by controlling the real-space
topology via epitaxy.
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All authors Elizabeth Skoropata, Peter M. Derlet, Hiroki Ueda, Roman Mankowsky, Mathias Sander, Henrik T. Lemke, Rafael T. Winkler, Yunpei Deng, Milan Radovic, Matteo Savoini, Biaolong Liu, Martina Basini, Vladimir Ovuka, Steven L. Johnson, Marta D. Rossell, Urs Staub
Materials Science · Cross-listed from physics.chem-ph
Quantum nuclear and band-dispersion effects recover near-UV absorption in short-hydrogen-bonded organic crystals
Jonas Hänseroth, Max Großmann, Malte Grunert et al. (+4 more)
Near-UV optical absorption is increasingly reported in hydrogen-bonded organic and biomolecular materials lacking aromatic or extended pi-conjugated chromophores, yet its microscopic origin remains unresolved and electronic-structure calculations often overestimate experimental absorption onsets. Here, we combine machine-learned interatomic potentials for large-scale classical and
quantum nuclear sampling with periodic excited-state calculations to address this discrepancy in L-pyroglutamine ammonium, an experimentally established glutamine-derived
crystal containing a well-resolved short hydrogen bond and exhibiting non-aromatic near-UV optical response. Using controlled in silico ion substitutions that vary the surrounding hydrogen-bond environment while preserving this scaffold, we compute optical spectra from configurations sampled along classical and
quantum nuclear trajectories using hybrid-functional time-dependent density functional theory. We show that
nuclear quantum effects stabilise
proton-sharing configurations that are strongly suppressed classically, redshifting the lowest bright excitations by 0.5-0.8 eV and raising the fraction of configurations with bright excitations below 6 eV from approximately 3% to approximately 30%. Explicit Brillouin-zone sampling provides a further, mechanistically distinct
redshift of 0.5-1.1 eV, reflecting modest but significant indirect electronic character. Only when both effects are incorporated does the calculated onset recover the experimental 3.8-4.5 eV range. These results establish
quantum proton fluctuations and reciprocal-space convergence as cooperative but physically distinct ingredients required for predictive optical spectroscopy of strongly hydrogen-bonded molecular materials.
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All authors Jonas Hänseroth, Max Großmann, Malte Grunert, Ali Hassanali, Erich Runge, Christian Dreßler, Muhammad Nawaz Qaisrani
Materials Science · Cross-listed from cond-mat.soft
Thermal stability of vapor-deposited stable glasses of an organic semiconductor
Diane M. Walters, Ranko Richert and M. D. Ediger
Vapor-deposited organic glasses can show enhanced kinetic stability relative to
liquid-cooled glasses. When such stable glasses of model glassformers are annealed above the glass transition temperature Tg, they lose their thermal stability and transform into the supercooled
liquid via constant velocity propagating fronts. In this work, we show that vapor-deposited glasses of an organic
semiconductor, N,N-bis(3-methylphenyl)-N,N-diphenylbenzidine (TPD), also transform via propagating fronts. Using spectroscopic ellipsometry and a new high-throughput annealing protocol, we measure transformation front velocities for TPD glasses prepared with substrate temperatures (TSubstrate) from 0.63 to 0.96 Tg, at many different annealing temperatures. We observe that the front velocity varies by over an order of magnitude with TSubstrate, while the activation energy remains constant. Using dielectric spectroscopy, we measure the structural relaxation time of supercooled TPD. We find that the mobility of the
liquid and the structure of the glass are independent factors in controlling the thermal stability of TPD films. In comparison to model glassformers, the transformation fronts of TPD have similar velocities and a similar dependence on TSubstrate, suggesting universal behavior. These results may aid in designing active layers in organic electronic devices with improved thermal stability.
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Materials Science
Fractional Magnonic Frequency Combs
Qian-Nan Huang, Zhiping Xue, Xudong Wang et al. (+5 more)
Magnonic frequency combs (MFCs) are spectacular phenomena in microwave-driven high-quality magnets. Like the equally spaced prongs in a comb, conventional integer MFCs are sharp resonances with an equal and constant frequency difference. Here we report fractional MFCs in a high-quality
magnetic sphere that emerges when adding a low-power, precisely detuned microwave to the main drive that compresses the frequency spacings to a rational fraction of the original comb, generating high-density spectral grids with hundreds of lines. The theoretical analysis finds that parametric three-
magnon scattering is the dominant non-linear process that reproduces the observation well. This mechanism is unique to magnets: it does not exist in an optomechanical system, where the Kerr and optical nonlinearities govern comb formation at a much higher power input. Since our platform operates as a frequency “vernier caliper" with much higher sensitivity than integer MFCs, it has application potential in precision metrology.
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All authors Qian-Nan Huang, Zhiping Xue, Xudong Wang, Yanmeng Lei, Lihui Bai, Ke Xia, Gerrit E. W. Bauer, Tao Yu
Materials Science · Cross-listed from cond-mat.soft
Limited surface mobility inhibits stable glass formation for 2-ethyl-1-hexanol
M. Tylinski, M. S. Beasley, Y. Z. Chua et al. (+2 more)
Previous work has shown that vapor-deposition can prepare organic glasses with extremely high kinetic stabilities and other properties that would be expected from
liquid-cooled glasses only after aging for thousands of years or more. However, recent reports have shown that some molecules form vapor-deposited glasses with only limited kinetic stability when prepared using conditions expected to yield a stable glass. In this work, we vapor deposit glasses of 2-ethyl-1-hexanol over a wide range of deposition rates and test several hypotheses for why this molecule does not form highly stable glasses under normal deposition conditions. The kinetic stability of 2-ethyl-1-hexanol glasses is found to be highly dependent on the deposition rate. For deposition at Tsubstrate = 0.90 Tg, the kinetic stability increases by 3 orders of magnitude (as measured by isothermal transformation times) when the deposition rate is decreased from 0.2 nm/s to 0.005 nm/s. We also find that, for the same preparation time, a vapor-deposited glass has much more kinetic stability than an aged
liquid-cooled glass. Our results support the hypothesis that the formation of highly stable 2-ethyl-1-hexanol glasses is inhibited by limited surface mobility. We compare our deposition rate experiments to similar ones performed with ethylcyclohexane (which readily forms glasses of high kinetic stability); we estimate that the surface mobility of 2-ethyl-1-hexanol is more than 4 orders of magnitude less than that of ethylcyclohexane at 0.85 Tg.
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All authors M. Tylinski, M. S. Beasley, Y. Z. Chua, C. Schick, M. D. Ediger
Materials Science
Multicomponent Grain Boundary Segregation Dilute-Limit Model and Its Effect on Nanocrystalline Stability
Georgiy Marchiy, Feodor Kuznetsov, Dmitry Samsonov et al. (+1 more)
Grain boundary segregation of solutes is a powerful tool for stabilizing nanocrystalline materials against grain growth. However, analytical models have been largely restricted to binary systems, leaving the stabilization potential of multicomponent
alloys poorly understood. In this work, we develop an analytical framework for an arbitrary number of solutes in the dilute limit of grain boundary concentrations based on segregation energy spectra computed via molecular dynamics. We demonstrate that multicomponent segregation synergistically expands the range of nanocrystalline
alloys that are thermodynamically stable against both grain growth and phase separation. Crucially, the model reveals that the cosegregation of almost any solutes enhances stability against phase separation, while the cosegregation of solutes with anti-correlated segregation spectra can suppress temperature-driven desegregation. This framework proposes a predictive tool for the rational design of thermally stable nanocrystalline
alloys using multicomponent doping.
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All authors Georgiy Marchiy, Feodor Kuznetsov, Dmitry Samsonov, Eugene Mukhin
Materials Science · Cross-listed from cond-mat.mes-hall
Enabling Electrical Readout of Néel vector reversal in a van der Waals Antiferromagnet
Raghvendra Posti, Ravi Kumar Bandepalli, Wenhao Liu et al. (+14 more)
Owing to its robustness against external perturbations and intrinsically ultrafast dynamics, the Néel vector in antiferromagnets (AFMs) can enable the development of next-generation spintronic and magnonic devices for
memory and computing applications. To realize AFM-based
magnetic memory devices, one of the key requirements is to demonstrate electrical readout of 180-degree reversal of Néel vector in thin film AFMs, which remains critically missing. In this work, we report experimental demonstration of a novel transport methodology to detect Néel vector reversal in atomically thin films of a van der Waals (vdW) based A-type AFM. For this, we utilize
spin-dependent electronic band properties of CrSBr by coupling it to a
spin-polarized layer, separated by a tunnel barrier. In this configuration, the
spin-dependent tunnelling magnetoresistance (MR) becomes sensitive to the relative orientation between the magnetization of the reference electrode and the interfacial sublattice magnetization of the AFM layer, in turn enabling electrical detection of the Néel vector orientation. Importantly, the observed MR can also reveal 180-degree reversal of Néel vector in even-layers of CrSBr, wherein adjacent sublattice
magnetic layers are exactly compensated and the net magnetization vanishes and thus establishes a broadly applicable strategy for electrical detection of Néel vector in vdW-based AFMs.
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All authors Raghvendra Posti, Ravi Kumar Bandepalli, Wenhao Liu, Anshuman Sahoo, Pratyush Saud, Zixin Zhai, Aswin L. N. Kondusamy, Zhenhong Cui, I-Hsuan Kao, Aalok Tiwari, Thomas Poirier, James H. Edgar, Kenji Watanabe, Takashi Taniguchi, Bing Lv, Jyoti Katoch, Simranjeet Singh
Materials Science
Breaking Bottlenecks in Solid Electrolyte Discovery with Large Artificial Intelligence Models
Eric Jianfeng Cheng, Min Hong, Zhiquan Zeng et al. (+22 more)
Solid electrolytes (SEs) are central to next-generation metal batteries, yet their discovery remains constrained by fragmented data, limited transferability of simulations, and slow experimental iteration. Unlike catalysis, where surface reactivity dominates, SEs require simultaneous optimization of bulk ion transport, defect chemistry, mechanical integrity, and interfacial stability. Here, we outline a framework for autonomous SE discovery enabled by large artificial intelligence (AI) models, including machine learning interatomic potentials (MLIPs) and large
language models (LLMs). We discuss the
evolution from static materials databases to dynamic, self-updating knowledge systems, the role of MLIPs in bridging density functional theory (DFT) and long-timescale ion migration, and the emergence of LLMs as engines for literature mining, hypothesis generation, and scientific
reasoning. We further describe a closed-loop architecture integrating AI-driven candidate design, multiscale simulation, uncertainty-aware selection, and experimental validation. Such systems shift SE research from intuition-guided exploration to data-informed, self-improving cycles. We conclude by highlighting challenges in data standardization, interfacial complexity, and reproducibility, and we propose design principles for building autonomous laboratories for solid-state battery materials.
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All authors Eric Jianfeng Cheng, Min Hong, Zhiquan Zeng, Chuanyu Liu, Qian Wang, Melissa Jane Meadowcroft, Vlad Badilita, Carlos Miguel Costa, Senentxu Lanceros-Méndez, Ying Li, Chenyao Ma, Weibo Gong, Surendra Martha, Aloysius Soon, Piao Ma, Di Zhang, Teguh Ariyanto, Sudaryanto, Hiroshi Kakinuma, Jie Zhao, Jiayu Peng, Pengfei Ou, Jun Lu, Shin-ichi Orimo, Hao Li
Materials Science
Dimensional Confinement Driven Scattering Inversion in NaCrTe$_2$
Himanshu Sharma, Bhawna Sahni, Tanusri Saha-Dasgupta et al. (+1 more)
Dimensionality reduction provides a powerful route to tune the electronic and
magnetic properties of van der Waals materials, yet its influence on electronic transport remains complex due to competing effects from
quantum confinement and modified scattering mechanisms. Here, we investigate this interplay in an
antiferromagnetic semiconductor $\text{NaCrTe}_2$ using first-principles calculations combined with the Boltzmann transport equation beyond the constant relaxation time approximation. Our results show that the monolayer limit induces a coupled magnetostructural reconstruction, reducing the band gap from $0.44$ eV (bulk) to $0.15$ eV (monolayer) and significantly enhancing the static dielectric constant. This
evolution triggers a fundamental scattering inversion: whereas bulk transport is limited by polar optical
phonon (POP) scattering, the monolayer becomes dominated by acoustic deformation potential (ADP) scattering. We show that this crossover originates from the simultaneous suppression of the Fröhlich interaction through enhanced dielectric screening and the amplification of acoustic scattering due to pronounced
lattice softening. These results clarify how the interplay between dielectric screening,
lattice stiffness, and band
topology governs transport in low-dimensional
magnetic semiconductors, providing a framework to optimize their electronic performance.
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All authors Himanshu Sharma, Bhawna Sahni, Tanusri Saha-Dasgupta, Aftab Alam
Materials Science
Quintic-Anharmonicity-Assisted Three-Phonon Scattering: A Previously Overlooked Same-Order Channel to Four-Phonon Scattering
Yi Xia
Four-
phonon scattering is widely regarded as the leading higher-order anharmonic correction to conventional three-
phonon description of anharmonic scattering and
lattice thermal transport. Here we show that diagrammatic perturbation theory contains another
phonon linewidth contribution of the same perturbation order, arising from the coupling between cubic and quintic anharmonic vertices. We derive and implement this contribution from first principles and identify it as a quintic-anharmonicity-assisted three-
phonon scattering channel. Although this process shares energy-conservation structure of the conventional three-
phonon process, its perturbative order and temperature dependence resemble those of the conventional four-
phonon process. For Si, we find that
phonon scattering from this additional channel is comparable to four-
phonon scattering over a broad frequency and temperature range, leading to a similar accelerated reduction of
lattice thermal conductivity at high temperatures. We further show that in strongly anharmonic AgCl, this channel can become comparable to the ordinary three-
phonon scattering even at room temperature. These results demonstrate that the commonly observed high-temperature enhanced scattering and suppression of
lattice thermal conductivity might not be attributed uniquely to four-
phonon process, and establish quintic-anharmonicity-assisted three-
phonon scattering as a previously overlooked same-order channel in anharmonic
lattice dynamics, which may be leveraged to uncover hidden microscopic thermal transport mechanisms.
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Materials Science · Cross-listed from cond-mat.dis-nn
The Physics of Topological Defects in Glasses
Arabinda Bera, Peter Schall, Timothy W. Sirk et al. (+2 more)
Topological defects play a central role in the mechanical behavior of crystalline materials, yet their relevance to amorphous solids has only recently begun to emerge. Over the last few years, theoretical, computational, and experimental studies have revealed the presence of well-defined topological invariants in vibrational eigenmodes, non-affine displacement fields, and deformation-induced vector fields of glasses. These defects have been shown to correlate strongly with soft spots, localized plastic rearrangements, yielding, and shear-band formation, suggesting a new perspective on the microscopic origins of plasticity in disordered materials. In this review, we provide a comprehensive overview of recent developments in the rapidly growing field of topological defects in glasses. We discuss the underlying theoretical concepts, including Burgers vectors, non-affine plasticity, vibrational modes, and topological invariants, and review recent numerical and experimental advances. Finally, we assess the current achievements, limitations, and open questions, and discuss future directions toward a unified topological description of plasticity and mechanical failure in amorphous solids.
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All authors Arabinda Bera, Peter Schall, Timothy W. Sirk, Vijayakumar Chikkadi, Alessio Zaccone
Materials Science
Proximity-Induced Spin Reorientation in Monolayer CrI$_3$ on Hexagonal WTe$_2$
Dániel Tibor Pozsár, Marcell Balázs Sípos, Amador García-Fuente et al. (+7 more)
Magnetic anisotropy controls the orientation and thermal stability of two-dimensional
magnetic order. Predicting proximity-induced changes in anisotropy requires linking the electronic structure to microscopic
magnetic interactions and finite-temperature behavior. Here we study monolayer CrI$_3$ on hexagonal WTe$_2$ using a first-principles-to-finite-temperature workflow centered on relativistic
spin-
Hamiltonian mapping. We find that WTe$_2$ reorients the CrI$_3$ magnetization from out-of-plane to in-plane and substantially enhances the
magnetic ordering scale within the extracted
spin models. Analysis of the extracted
spin Hamiltonians shows that the reorientation is driven by a substrate-induced change in the balance between symmetric anisotropic exchange and onsite anisotropy. We establish a transferable workflow for proximity-controlled magnetism in two-dimensional van der Waals
heterostructures.
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All authors Dániel Tibor Pozsár, Marcell Balázs Sípos, Amador García-Fuente, Péter Nemes-Incze, Viktor Ivády, Efrén Navarro-Moratalla, Jaime Ferrer, László Szunyogh, László Oroszlány, Zoltán Tajkov
Materials Science
One-dimensional self-organization of water molecules in proton conducting Andersson-Wadsley titanates
Mathilde Arnaud, Guillaume Benas, Narimane Meziani et al. (+13 more)
Layered alkali titanates with M 2 Ti 2 O 5 chemical formula (MTO, M=K,Rb) belonging to the Andersson-Wadsley perovskite family spontaneously incorporate water to form MTO.(H 2 O) x compounds, which exhibit superionic conductivity. At very low hydration x, scanning electron microscopy evidences one-dimensional heterogeneous patterns oriented along ___ b that are arranged in an orderly manner. At higher hydration, the material is observed to spontaneously exfoliate by creating (001) surfaces. Simulations carried out using Density Functional Theory reveal an ordered arrangement of the guest water molecules in Rb 2 Ti 2 O 5 , with strong hydrogen bonds between the water molecules and the apical oxygen of the host
crystal. At low hydration x, the water molecules form self-organized one dimensional (1D) double chains along ___ b. Further increase of the water content leads to the creation of hydrated (001)-surfaces that are made of densely packed water chains in agreement with the infrared spectroscopy measurements. Rb 2 Ti 2 O 5 exhibits highly anisotropic
proton conductivity, with respect to the
crystal orientation, with super-ionic conductivity along ___ b reaching 3 mS/cm at room temperature after hydration. The combined observations and simulations suggest that these water chains are thus at the root of fast
proton conduction, which is likely powered by a Grotthuss-like mechanism.
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All authors Mathilde Arnaud, Guillaume Benas, Narimane Meziani, Armel Descamps-Mandine, Claudie Josse, Sophia Akkari, Thierry Douillard, Sofia de Sousa Coutinho, Mélanie de Vos, Stéphane Holé, Gwenaëlle Rousse, Rémi Federicci, Sylvain Franger, Paola Giura, Fabio Finocchi, Brigitte Leridon
Materials Science
Nonradiative Multiphonon Model of Deep-Level Transient Spectroscopy: Beyond Henry-Lang Model
Menglin Huang, Shanshan Wang, Junjie Zhou et al. (+2 more)
Deep-level transient spectroscopy (DLTS) is a key experimental method for defect characterization, yet its analysis remains controversial, and the two widely used models developed by Henry and Lang are conflicting. We show that the Henry-Lang model is valid only under the Condon approximation, as well as high-temperature and strong electron-
phonon coupling approximations, which cause incorrect temperature dependence of carrier emission and capture. Here we develop a rigorous nonradiative multiphonon (NMP) model, and demonstrate that the temperature dependence is governed predominantly by effective
phonons with large
phonon wavefunction overlap and high thermal occupation. The effective
phonons are strongly correlated with
lattice relaxation.The neglect of this correlation in existing DLTS models introduces substantial errors when they are used to fit DLTS-measured emission rates. Our comparison for 21 different defects in 12
semiconductors, including Si, SiC and Ga$_2$O$_3$, shows that the Henry-Lang model gives a completely different temperature dependence of carrier capture cross section from that obtained using the rigorous NMP model, with errors reaching up to six orders of magnitude at room temperature. Our study highlights the necessity of revisiting previous DLTS analysis studies using the rigorous NMP model.
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All authors Menglin Huang, Shanshan Wang, Junjie Zhou, Xinjing Guo, Shiyou Chen
Materials Science · Cross-listed from cond-mat.str-el
Fluctuation exchange study on the electron-hole asymmetry of the superconductivity across 1/3 filling in the trilayer Hubbard model
Yushi Yamada, Masataka Kakoi, Masayuki Ochi et al. (+1 more)
We study within the fluctuation exchange approximation the trilayer Hubbard model where three layers of the Hubbard model are coupled by large interlayer hoppings so that the overlap of the bonding, nonbonding, and antibonding bands is relatively small. We pay special
attention to the band fillings close to 1/3, for which the bonding and nonbonding bands as a whole are close to half filling. For relatively small values of the onsite $U$, superconductivity roughly exhibits electron-hole symmetric behavior, as expected for a nearly half-filled two-band system. By contrast, an asymmetry appears when $U$ becomes large, where superconductivity is more favored in the hole-doped regime, i.e., in the regime where electrons are removed from 1/3 filling. We attribute this asymmetry to the asymmetric renormalization of the bonding, nonbonding, and antibonding bands when $U$ is large.
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All authors Yushi Yamada, Masataka Kakoi, Masayuki Ochi, Kazuhiko Kuroki
Materials Science
Low-temperature magnetic-field-driven thermal oscillator based on metal-superconductor joint
Poonam Rani and Yoshikazu Mizuguchi
Thermal control is one of the important technologies for fundamental science and thermal management. Among them, thermal oscillators have been in demands in the field of materials science and device application. In general, flexible frequency, amplitude, and waveform are needed for useful thermal oscillator, and the stability of the average temperature is also highly required. However, thermal oscillators based on an AC-current-driven heater require complicated control of input power to achieve the above-mentioned flexibility and stability of the outputs. Here, we demonstrate that magnetically-driven thermal oscillators fabricated using a metal-
superconductor (Cu-Pb) joint achieve those requirements easily by tuning the applied
magnetic field (H). A DC-current-driven heater is attached on the metal (Cu) side, and the
superconductor (Pb) edge is attached to thermal bath. We use a sharp and huge change in thermal conductivity at the superconducting transition of the Pb wire to generate thermal oscillation at the Cu-wire side. A sine-shaped thermal oscillation with an amplitude of 180 mK and a frequency of 0.17 Hz is observed with highly stable average temperature. Furthermore, a larger amplitude is achieved in a square-shaped oscillation with a larger H amplitude. Our thermal oscillator with temperature stability, large amplitude, and relatively high frequency will work as a flexible AC heat source at cryogenic temperatures.
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Materials Science
Reversible non-equilibrium phase transformation in amorphous germanium
Yang Huang, Marek Mihalkovič and Michael Widom
First principles molecular dynamics simulations of germanium reveal a reversible
liquid-glass transition below the
equilibrium melting point with a wide hysteresis loop. Direct calculation of the
liquid and amorphous state free energies, enabled by absolute
entropy calculations, verify that the transition is first order in character between two metastable phases. These results lend credence to models of explosive recrystallization from amorphous Ge thin films, through a metastable
liquid state and finally reaching the low temperature crystalline structure.
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