Materials Science
Highly Efficient Functionalization of hBN with Lithium Oxalate: A Multifunctional Platform for Composites, Ion Transport, and Spin Labeling
Bence G. Márkus, Anna Nyáry, Dávid Beke et al. (+18 more)
Multifunctional solid-state materials are crucial for enabling safer and simpler lithium battery architectures. Here we report a scalable, solvent-free mechanochemical strategy to overcome the chemical inertness of hexagonal boron nitride and produce Li$_2$(BN)$_6$C$_2$O$_4$ (LBNCO), a lithium-rich boron nitride nanostructure. High-energy milling simultaneously exfoliates hBN and induces robust covalent oxalate functionalization, yielding a nanocrystalline lamellar compound with intrinsically incorporated lithium. LBNCO exhibits Li$^+$ ionic conductivity, electronic insulation, and thermal stability exceeding $350~^{\circ}$C. Additional mechanochemical processing enables further lithium enrichment without compromising chemical stability, allowing tunable ionic conductivity. By integrating ion transport, mechanical robustness, and thermal stability within a single material, LBNCO establishes a new platform for solid-state lithium batteries and related technologies.
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All authors Bence G. Márkus, Anna Nyáry, Dávid Beke, Lili Vajtai, Sivaviswa Radhakrishnan, Vignyatha R. Tatagari, Bradlee J. McIntosh, Adil Saleem, Changlong Chen, Balázs Zsirka, Mandefro Y. Teferi, Jens Niklas, Oleg G. Poluektov, Ira D. Bloom, Fulya Dogan, Margit Kovács, Ferenc Simon, Gábor Szalontai, Leon Shaw, László Forró, Károly Németh
Materials Science
Nonlinear phononic slidetronics
Pooja Rani and Dominik M. Juraschek
Van der Waals ferroelectrics are conventionally switched by sliding the different layers between stacking orders with opposing electric polarizations. Ultrashort
laser pulses have been proposed to launch shear modes and induce switching, with often unfeasible large pulse energies however. Here, we demonstrate switching of ferroelectricity in
bilayer hexagonal boron nitride through nonlinearly excited
phonons. We show that the efficiencies of conventional coherent
phonon excitation mechanisms, including infrared absorption and Raman scattering techniques, are too low to overcome the energy barrier separating the two ferroelectric states. We demonstrate instead that excitation of high-frequency intralayer modes leads to a tilting of the interlayer potential-energy landscape that enables changing the stacking order. Our results provide an avenue towards efficient phononic slidetronics, enabling ultrafast control of the stacking order in van der Waals materials.
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Materials Science
Highly Tunable Phonon Polaritons via Metal Intercalation
Mariia Stepanova, Minh Ngo, Mashnoon Alam Sakib et al. (+5 more)
Phonon polaritons in van der Waals
crystals offer mid-infrared light confinement deep below the diffraction limit, making them promising for nanophotonics applications. However, the practical use of
phonon polaritons remains limited, in part due to the lack of precise control over the
phonon polariton dispersion, as
crystal lattice vibrations are often inert to external stimuli. Here, we address this challenge by zerovalent metal intercalation of $\alpha$-MoO$_3$. Photo-induced force microscopy shows that introducing tin into the van der Waals gap modulates the
phonon polariton dispersion by up to $38.5\pm0.5\%$, which is the highest amount of tunability among non-mechanical modulation approaches, to the best of our knowledge. Intercalation with various metal species preserves the
phonon polariton lifetimes, while modulating the dielectric permittivity in agreement with the density functional theory and analytical calculations. Our results establish metal intercalation as a practical route to reconfigurable mid-infrared nanophotonics.
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All authors Mariia Stepanova, Minh Ngo, Mashnoon Alam Sakib, Wills Harris, Joshua Bocanegra, Ruqian Wu, Kristie J. Koski, Maxim R. Shcherbakov
Materials Science
Unravelling the oxygen influence in cubic bixbyite In$_2$O$_3$ on Raman active phonon modes by isotope studies
Johannes Feldl, Roland Gillen, Janina Maultzsch et al. (+5 more)
In this study, we performed comprehensive investigations on the Raman active
phonon modes in cubic bixbyite In$_2$O$_3$, an important
oxide based, wide-bandgap
semiconductor. Fundamental insights into the
lattice dynamics are revealed, by determining the atomistic contribution to all modes and their frequencies by density functional perturbation theory calculations. Those simulations were performed for different compositions of $^{16}$O and $^{18}$O isotope ratios, including their pure states. An increasing red-shift of the mode frequencies with increasing $^{18}$O content for all modes, due to the increased atomic mass, is revealed. For the seven lowest energy modes, this relative shift is below 1%, whereas for the remaining 15 higher energetic modes a shift of about 5.5% was identified. All modes have energy contributions of both indium and oxygen
lattice sites, except for one, which corresponds to a pure oxygen vibrational state. Applying Raman spectroscopy, those results could be verified experimentally with excellent agreement. Investigated samples consisted of a bulk single
crystal with $^{16}$O isotopes and a MBE grown thin film as the $^{18}$O sample. Time-of-flight secondary ion mass spectrometry confirms the purity of the oxygen isotope in the sample. These isotopologue studies allow for a direct experimental access to fundamental material properties in cubic In$_2$O$_3$ by means of Raman spectroscopy. For example, we speculate, that the presence of oxygen vacancies in In$_2$O$_3$ would result in a shift of modes that are dominated by O-vibrations, e. g., $E_{g}^{(4)}$ or $A_{g}^{(4)}$, towards lower frequencies.
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All authors Johannes Feldl, Roland Gillen, Janina Maultzsch, Alexandra Papadogianni, Joe Kler, Zbigniew Galazka, Oliver Bierwagen, Manfred Ramsteiner
Materials Science
First-principles study of phase stability and magnetic properties of B2 AlCr, AlMn, AlFe, AlCo and AlNi aluminides
Haireguli Aihemaiti, Esmat Dastanpour, Anders Bergman et al. (+1 more)
Using ab initio Density Functional Theory (DFT) calculations, we investigate the electronic structure, phase stability, and
magnetic properties of equiatomic binary
alloys between Al and 3d
magnetic transition elements (Cr, Mn, Fe, Co, and Ni). Thermodynamically, all five binary aluminides are more stable in the ordered B2 phase than in the disordered body centered cubic phase, and Co is found to be the strongest B2 forming element with Al. The AlCo and AlNi compounds with B2 structure are verified to be non-
magnetic, whereas AlFe turns out to be weakly
magnetic, which is consistent with other DFT calculations employing similar exchange-correlation approximations.
Magnetic simulations based on the Heisenberg
Hamiltonian predict an
antiferromagnetic ground state for the hypothetical B2 AlCr, which is also confirmed by direct DFT calculations. Doping AlCr with Co leads to an
antiferromagnetic to
ferromagnetic transition, where ferromagnetism is to a large extent attributed to Cr atoms. The phase stability and
magnetic trends are explained using electronic structure arguments. The present findings contribute to a deeper understanding of the phase stability and
magnetic properties of AlX binary
alloys, providing insights into the formation mechanisms of the B2 structure with 3d
magnetic transition metals.
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All authors Haireguli Aihemaiti, Esmat Dastanpour, Anders Bergman, Levente Vitos
Materials Science
Haireguli Aihemaiti, Esmat Dastanpour, Shashank Chaturvedi et al. (+3 more)
Using Density Functional Theory (DFT) calculations and Monte-Carlo (MC) simulations, we investigate the recently reported
magnetic transition in B2 Al-Cr-Co
alloys. The Cr sublattice is alloyed with different amounts of Co in the
antiferromagnetic (AFM) B2 AlCr binary
alloy and the resulting exchange interactions are analyzed within the Heisenberg
Hamiltonian framework. DFT results reveal that at low Co concentrations the system favors the AFM order, while at high Co contents a transition to the
ferromagnetic (FM) state is observed. Within the FM stability field, the Curie temperature (TC), obtained within the mean-field approximation, is below ~160 K and decreases with Co concentration. The calculated exchange parameters evolve systematically with Co content, and the trends are consistent with the DFT total energies. The
magnetic configurations obtained from MC simulations follow the DFT results at low Cr levels but predict a
spin-glass behavior for
alloys containing more than 40 at.% Co on Cr sublattice. These findings provide a fundamental understanding of how the chemistry-driven changes in exchange interactions affect magnetism in the B2 Al-Cr-Co
alloys.
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All authors Haireguli Aihemaiti, Esmat Dastanpour, Shashank Chaturvedi, Shuo Huang, Anders Bergman, Levente Vitos
Materials Science
Altermagnetism, Kagome Flat Band, and Weyl Fermion States in Magnetically Intercalated Transition Metal Dichalcogenides
Avinash Sah, Ting-Yong Lim, Clayton Conner et al. (+5 more)
Altermagnetic (AM) compounds have recently emerged as a promising platform for realizing unconventional
quantum phases, enabled by their unique
spin-split band structure at zero net magnetization. Here, we present a first-principles investigation of magnetically intercalated transition metal dichalcogenides (TMDs) of the form XY$_4$Z$_8$ (X $=$ Mn, Fe, Co, Ni, Cr, or V; Y $=$ Nb or Ta; and Z $=$ Se or S), identifying a subset of new versatile AM candidates. Our results establish a systematic correlation between interatomic geometry, quantified by the ratio of interlayer to intralayer spacing, and the
magnetic ground states. Systems with A-type
antiferromagnetic order exhibit momentum-dependent
spin splitting consistent with AM behavior. The combination of the AM
spin-splitting and the
spin-orbit coupling leads to the emergence of Weyl nodes together with the corresponding topological
Fermi arc surface states. Moreover, we identify flat bands near the
Fermi level that originate from the intercalant-induced formation of an effective kagome-like sublattice in the TMD layer. These results collectively establish magnetically intercalated TMDs as a promising platform for engineering altermagnetism, flat bands, and Weyl
fermions within a single material family, facilitating the development of topological and spintronic applications.
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All authors Avinash Sah, Ting-Yong Lim, Clayton Conner, Amarnath Chakraborty, Giovanni Vignale, Tay-Rong Chang, Pavlo Sukhachov, Guang Bian
Materials Science
The Piezochiral Effect
Z. Zeng, M. Först, M. Fechner et al. (+3 more)
Chirality is a pervasive property of matter that underpins many important phenomena across physics, chemistry and biology. Given its broad significance, the development of protocols for rational control of chirality in solid state systems is highly desirable, especially if this effect can be tuned continuously and in two directions. Yet, this goal has remained elusive due to the absence of a universal conjugate field that couples linearly to this structural order. Here, we introduce the piezochiral effect, which enables control of chirality through mechanical strain. We first show by
symmetry analysis that uniaxial strain induces chirality in a broad class of achiral
crystals that host fragments of opposite chirality within each unit
cell, an effect that has so far remained unrecognized. The strain-induced handedness can be tuned either by changing the strain direction or by switching between compressive and tensile strain. We experimentally verify this effect in AgGaS2, using measurements of the optical activity under strain. Our discovery establishes a new scheme for chirality control, with potential applications that range from spintronics to asymmetric catalysis, and enantioselective interactions in biosystems.
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All authors Z. Zeng, M. Först, M. Fechner, X. Deng, A. Cavalleri, P.G. Radaelli
Materials Science
Tailoring dispersion and evanescent modes in multimodal nonlocal lattices using positive-only interactions
Lucas Rouhi and Christophe Droz
Metamaterials derive their unconventional properties from engineered microstructures, with periodic
lattices providing a versatile framework for modeling wave propagation. Dispersion relations, obtained from Bloch-Floquet theory, govern how waves propagate, attenuate, or localize within such systems. Extending interactions beyond nearest neighbors, through nonlocality, substantially enriches the design space of band diagrams, enabling phenomena such as negative or zero group velocities, roton-like extrema, and band-gap localization. However, existing approaches to dispersion tailoring often rely on analytical formulations or
Fourier-based identifications, which become impractical for complex coupling mechanisms and offer limited control over physical constraints such as stiffness positivity. This work introduces a general interpolation-based framework for customizing dispersion relations in uniform nonlocal
lattices. Rather than reconstructing full dispersion curves, the method enforces prescribed frequency-wavenumber points as interpolation constraints, enabling localized and tunable control of wave behavior. The formulation is applied to both spring- and beam-interaction
lattices, and demonstrated on an Euler-Bernoulli beam model with adjustable nonlocal couplings. Through systematic parameter tuning, the framework enables the creation of rotons, the adjustment of group-velocity dispersion, and the design of evanescent waves with controlled exponential decay within band gaps, all while ensuring real, positive-only stiffness parameters and passive mechanical behavior. Altogether, this parametric interpolation strategy provides a physically consistent and computationally efficient route for engineering advanced phononic functionalities in periodic nonlocal systems.
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Materials Science
Zeeman Spectroscopy of Vacancy-Charge-Compensated Er3+ Sites in CaWO4 under Vector Magnetic Fields
Fabian Becker, Sudip KC, Lorenz J. J. Sauerzopf et al. (+4 more)
We present polarization-resolved optical absorption measurements on Er3+ ions in CaWO4 under vector
magnetic fields, focusing on charge-compensated sites arising from local Ca2+ vacancies. While the known axial Er3+ site displays a single symmetric Zeeman-split transition pattern consistent with S4
symmetry, two additional sites exhibit more complex spectral behavior, including sets of transitions that interchange under 90{\deg}
crystal rotations-evidence of reduced, rhombic-like
symmetry. From these polarization- and temperature-dependent spectra, we extract effective g-factors. Our findings are corroborated by electron paramagnetic resonance measurements and support a model of multiple inequivalent Ca2+ vacancies around Er3+ sites in the host
lattice. This detailed characterization contributes to understanding defect-engineered rare-earth sites for
quantum information applications.
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All authors Fabian Becker, Sudip KC, Lorenz J. J. Sauerzopf, Tim Schneider, Luis Risinger, Christian Schmid, Kai Müller
Materials Science
Hexagonal InOI monolayer: a 2D phase-change material combining topological insulator states and piezoelectricity
Wenhui Wan, Xinyue Liu, Yanfeng Ge et al. (+2 more)
Two-dimensional (2D) phase-change materials (PCMs) with moderate transition barriers and distinctly contrasting properties are highly desirable for multifunctional devices, yet such systems remain scarce. Using first-principles calculations, we propose a hexagonal InOI monolayer as a promising 2D PCM. This material exhibits two distinct polymorphs: an energetically favorable T$^{\prime}$ phase and a metastable T phase, differentiated by iodine atom positions. The T$^{\prime}$-to-T structural phase transition features a moderate energy barrier $E_b$ of 72.1 meV per formula unit, facilitating reversible switching. Notably, strain engineering tailors the electronic transition, inducing either a metal-to-topological-
insulator or a metal-to-normal-
insulator transformation. Additionally, this phase transition modulates the piezoelectric response and shifts optical absorption from the infrared to the visible range. These multifunctional properties make 2D hexagonal InOI highly promising for applications in non-volatile
memory, low-contact-resistance spintronics, and optical switching devices.
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All authors Wenhui Wan, Xinyue Liu, Yanfeng Ge, Ziqang Li, Yong Liu
Materials Science
Examining the Spin Structure of Altermagnetic Candidate MnTe Grown with Near Ideal Stoichiometry
Qihua Zhang, Christopher J. Jensen, Alexander J. Grutter et al. (+11 more)
Altermagnets are a recently-discovered class of materials with
magnetic ordering that have a zero net magnetization and a momentum-dependent
spin splitting in their band structure, arising from a collinear
spin arrangement with alternating polarizations in the
crystal lattice. The nickeline-structured manganese telluride ({\alpha}-MnTe) is an attractive altermagnet candidate due to its predicted large
spin splitting energy and a transition temperature near 300K. In this work, we present a thorough investigation of the
spin structure of {\alpha}-MnTe thin films grown by molecular beam epitaxy with very high
crystal quality and low residual magnetization. The epitaxial {\alpha}-MnTe films have a full-width-at-half-maximum of 0.1{\deg} as measured by x-ray-diffraction rocking curves and a root-mean-square roughness below 1 nm.
Neutron diffraction measurements confirm the
antiferromagnetic order in the {\alpha}-MnTe film and show a Néel temperature of 307 K. Polarized
neutron reflectometry detects a vanishingly small net magnetization which may be confined to the MnTe/InP interface, highlighting the near-ideal stoichiometry in the sample. In vacuo angle resolved photoemission spectroscopy reveals that the bulk band spectrum of the MnTe films is consistent with the weak altermagnetic order as theoretically predicted and observed for the high
symmetry nodal plane in the center of the Brillouin zone. This study establishes optimized growth conditions for the synthesis of stoichiometric {\alpha}-MnTe thin films which exhibit exceptional structural and
magnetic ordering, thereby providing a robust platform for the precise characterization of their altermagnetic properties.
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All authors Qihua Zhang, Christopher J. Jensen, Alexander J. Grutter, Sandra Santhosh, William D. Ratcliff, Julie A. Borchers, Thomas W. Heitmann, Narendirakumar Narayanan, Timothy R. Charlton, Mingyu Yu, Ke Wang, Wesley Auker, Nitin Samarth, Stephanie Law
Materials Science
2D Excitonics with Atomically Thin Lateral Heterostructures
S. Shradha, R. Rosati, H. Lamsaadi et al. (+18 more)
Semiconducting transition metal dichalcogenides (TMDs), such as MoSe$_2$ and WSe$_2$, exhibit unique optical and electronic properties. Vertical stacking of layers of one or more TMDs, to create
heterostructures, has expanded the fields of moiré physics and twistronics. Bottom-up fabrication techniques, such as chemical vapor deposition, have advanced the creation of
heterostructures beyond what was possible with mechanical exfoliation and stacking. These techniques now enable the fabrication of lateral
heterostructures, where two or more monolayers are covalently bonded in the plane of their atoms. At their atomically sharp interfaces, lateral
heterostructures exhibit additional phenomena, such as the formation of charge-transfer
excitons, in which the electron and hole reside on opposite sides of the interface. Due to the energy landscape created by differences in the band structures of the constituent materials, unique effects such as unidirectional
exciton transport and excitonic
lensing can be observed in lateral
heterostructures. This review outlines recent progress in
exciton dynamics and spectroscopy of TMD-based lateral
heterostructures and offers an outlook on future developments in excitonics in this promising system.
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All authors S. Shradha, R. Rosati, H. Lamsaadi, J. Picker, I. Paradisanos, Md T. Hossain, L. Krelle, L. F. Oswald, N. Engel, D. I. Markina, K. Watanabe, T. Taniguchi, P. K. Sahoo, L. Lombez, X. Marie, P. Renucci, V. Paillard, J.-M. Poumirol, A. Turchanin, E. Malic, B. Urbaszek
Materials Science
Lossy phononic metamaterials for valley manipulation
Shunda Yin, Qiuyan Zhou, Yuxiang Xi et al. (+5 more)
Non-Hermitian physics characterized by complex band spectra has established a new paradigm in condensed matter systems and metamaterials. Recently, non-Hermitian gain and nonreciprocity are deliberately introduced to valley manipulation, leading to various phenomena beyond the Hermitian scenarios, such as the amplified topological whispering gallery modes as an acoustic
laser. In contrast, pure loss is inevitable in practice and generally regarded as a detrimental factor. Here, we reveal that the coupling loss can manipulate valley degrees of freedom in a phononic metamaterial. Three distinct valley-related effects, including valley-resolved nonreciprocity that functions as a valley filter, valley-dependent skin effects where bulk states from different valleys localize at opposite boundaries, and valley-projected edge states with boundary-dependent lifetimes that leads to an anomalous beam splitting, are demonstrated through theoretical analysis and airborne sound experiments. Owing to the easy preparation of loss, our findings shed light on both non-Hermitian and valley physics and may facilitate innovative applications of valley-related devices.
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All authors Shunda Yin, Qiuyan Zhou, Yuxiang Xi, Weiyin Deng, Wei Chen, Jiuyang Lu, Manzhu Ke, Zhengyou Liu
Materials Science · Cross-listed from cond-mat.mes-hall
Controlling bubble and skyrmion lattice order and dynamics via stripe domain engineering in ferrimagnetic Fe/Gd multilayers
Tim Titze, Sabri Koraltan, Timo Schmidt et al. (+6 more)
Ferrimagnetic Fe/Gd multilayers host maze-like stripe domains that transform into a disordered bubble/skyrmion
lattice under out-of-plane
magnetic fields at ambient temperature. Femtosecond magneto-optics distinguishes these textures via their distinct coherent breathing dynamics. Crucially, applying a brief in-plane “set”
magnetic field to the stripe state enhances both frequency and amplitude of the bubble/skyrmion
lattice breathing mode. Lorentz transmission electron microscopy,
magnetic force microscopy, and micromagnetic simulations reveal that this enhancement arises from field-aligned stripes nucleating a dense, near-hexagonal bubble/skyrmion
lattice upon out-of-plane field application, with strong indications for a pure skyrmion
lattice. Thus, modifying the initial domain configuration by in-plane fields enables precise control of coherent magnetization dynamics on picosecond to nanosecond timescales and potentially even of
topology.
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All authors Tim Titze, Sabri Koraltan, Timo Schmidt, Mailin Matthies, Amalio Fernández-Pacheco, Dieter Suess, Manfred Albrecht, Stefan Mathias, Daniel Steil
Materials Science · Cross-listed from physics.app-ph
Combining metal dewetting and lateral etching for the scalable top-down fabrication of GaN nanowire arrays with independently tunable diameter and spacing
Jingxuan Kang, Rose-Mary Jose, Oliver Brandt et al. (+1 more)
The top-down fabrication of nanowires based on patterning via metal dewetting is a cost-effective and scalable approach that is particularly suited for applications requiring large arrays of nanowires. Advantageously, the nanowire diameter can be tailored by the initial metal film thickness. However, we show here that metal dewetting inherently leads to a coupling between the nanowire diameter and spacing. To overcome this limitation, we introduce two strategies that are exemplified for GaN nanowires: (i) modification of the surface and interface energies within the dewetting system, and (ii) thinning of the nanowires by lateral etching. In the first strategy, GaN(0001), SiOx, and SiNx substrate surfaces are combined with Au, Pt, and Pt-Au
alloy dewetting metals to tune the dewetting behavior. The differences in interface energies affect the relation between nanowire diameter and spacing, albeit within a limited range. The second strategy adds a lateral etching step to the conventional top-down nanowire fabrication process. This step at the same time reduces the nanowire diameter and increases the spacing, thus enabling combinations beyond the constraints of metal dewetting alone. When in addition different initial nanowire diameters are employed, it is possible to independently control diameter and spacing over a substantially extended range. Therefore, the inherent limitation of conventional dewetting-based patterning approaches for the top-down fabrication of nanowires is overcome.
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All authors Jingxuan Kang, Rose-Mary Jose, Oliver Brandt, Lutz Geelhaar
Materials Science
Toward more performant eye safe lasers: effect of increasing sensitizer amount in Yb3+,Er3+:YAG transparent ceramic on its spectral characteristics
Agnieszka Szysiak, Robert Tomala, Helena Węglarz et al. (+3 more)
Developing efficient Er3+,Yb3+:YAG eye-safe
lasers is a priority of modern
laser technology. This paper focuses on the influence of the concentration of Yb3+ ions on the spectroscopic properties of Er3+,Yb3+:YAG transparent ceramics. Four samples with different concentrations of Yb3+ ions were prepared by solid-state reaction sintering. The study revealed the influence of Yb3+ ions on the microstructure and the sintering process. A high concentration of Yb3+ ions leads to the formation of Y3+-rich
impurity phases and causes segregation of Er3+ and Yb3+ and Si4+ into these phases. The influence of Yb3+ ions on the shape of emission spectra and the lifetimes of both Er3+ and Yb3+ ions was shown. Changes in the spectroscopic properties were ascribed to increase in neat transfer between Yb3+ and Er3+ ions. IQE of Er3+ and Yb3+ luminescence were calculated, and optimal Er3+/Yb3+ ions ratio were proposed
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All authors Agnieszka Szysiak, Robert Tomala, Helena Węglarz, Juraj Kajan, Mirosław Słobodzian, Mykhailo Chaika
Materials Science · Cross-listed from cond-mat.mes-hall
Optimal spin-charge interconversion in graphene through spin-pseudospin entanglement control
Joaquín Medina Dueñas, Santiago Giménez de Castro, Jose H. Garcia et al. (+1 more)
The electrical generation of
spin signals is of central interest for spintronics, where
graphene stands as a relevant platform as its
spin-orbit coupling (SOC) is tuned by proximity effects. Here, we propose an enhancement of
spin-charge interconversion in
graphene by controlling the intraparticle
entanglement between the
spin and pseudospin degrees of freedom. We demonstrate that, although the
spin alone is not conserved in Rashba-Dirac systems, a combined
spin-pseudospin operator is conserved. This conserved quantity represents the interconversion between pure
spin and pseudospin textures to a
spin-pseudospin entangled structure, where Kane-Mele SOC tunes this balance. By these means, we achieve
spin-charge interconversion of 100% efficiency via the Rashba-Edelstein effect.
Quantum transport simulations in disordered micron-size systems demonstrate the robustness of this effect, and also reveal a disorder resilient
spin Hall effect generated by the interplay between Rashba and Kane-Mele SOC. Our findings propose a platform for maximally efficient
spin-charge interconversion, and establish
spin-pseudospin correlations as a mechanism to tailor spintronic devices.
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All authors Joaquín Medina Dueñas, Santiago Giménez de Castro, Jose H. Garcia, Stephan Roche
Materials Science
Temperature-Dependent Spectroscopy of Cr3+:YGG Nanophosphors with Multisite Emission
Mykhailo Chaika
An important feature of Cr3+ is the ability to tune the absorption and emission spectra by changing the host. However, in some cases, different emission spectra can be detected in samples with similar Racah parameters. The present paper reports changes in the luminescence properties of Cr3+:YGG nanocrystals. Cr3+:YGG nanocrystals were synthesized by a modified Pechini method to obtain nanocrystals containing two fractions of Cr3+:YGG nanocrystals with different
lattice parameters and crystalline sizes. The increase in the concentration of Cr3+ ions leads to a
redshift of the 4T2g emission from 750 nm to 850 nm for luminescence spectra measured at 80K. In contrast, room temperature luminescence spectra showed similarity in the shape of the emission spectra. The calculated
crystal field strength was found to increase with the concentration of Cr3+ ions, so the detected patterns in low-temperature luminescence spectra were explained by energy transfer chain processes.
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Materials Science
Multistability of interstitial magnesium and its carrier recombined migration in gallium nitride
Yuansheng Zhao, Kenji Shiraishi, Tetsuo Narita et al. (+1 more)
We present density-functional-theory calculations which provide a microscopic picture of the recombination-enhanced migration of interstitial Mg in GaN. We determine stable structures and migration pathways with accurate HSE approximation to the exchange-correlation energy, and also computed recombination rates using the obtained energy spectrum and wavefunctions. It is found that the migration between the most stable octahedral sites (Mg$_{\textrm{O}}$) via newly found interstitial complex structure shows the lowest migration energy in which one or two electrons are captured during the migration, that the most stable charge state of 2+ changes to 1+ or neutral, and that by this recombination of carriers the migration barrier is significantly reduced. Starting from Mg$_{\textrm{O}}^{2+}$, Mg captures an electron becoming the 1+ charge state and overcomes the barrier of 1.65 eV, much reduced from 2.23 eV in case of the migration with the 2+ charge state kept. Moreover, further electron capture is realized accompanied by substantial structural relaxation, thus Mg becoming neutral. Detailed HSE calculations for this second capture show that the migration barrier is 1.55 eV, thus clarifying the important role of the carrier recombination for Mg migration in GaN. These findings are corroborated by the present quantitative calculations of recombination rates based on electronic
Hamiltonian constructed from our DFT-obtained energy spectrum. The timescale of the recombination is clarified to be in or under the timescale of the migration with typical electron density and the enhancement is expected to be significant.
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All authors Yuansheng Zhao, Kenji Shiraishi, Tetsuo Narita, Atsushi Oshiyama
Materials Science · Cross-listed from cond-mat.mes-hall
The spinterface mechanism for the chiral-induced spin selectivity effect: A Critical Perspective
Subhajit Sarkar, Amos Sharoni, Oliver L. A. Monti et al. (+1 more)
The
chiral-induced
spin selectivity (CISS) effect, whereby
chiral molecules preferentially transmit electrons of one
spin orientation, remains one of the most intriguing and debated phenomena at the interface of spintronics, molecular electronics, and
quantum materials. Despite extensive experimental observations across diverse platforms - including transport junctions, photoemission, and enantioselective chemistry - a comprehensive theoretical framework is still lacking. In this perspective, we critically examine the spinterface mechanism as a unifying explanation for the CISS effect. The spinterface model, which hypothesizes a feedback interaction between electron motion in
chiral molecules and fluctuating surface
magnetic moments, is shown to quantitatively reproduce experimental data across various systems and conditions. We contrast it with some existing theoretical models, highlighting key experimental features. Importantly, we also address open questions and criticisms of this model, including the nature of surface magnetism, the role of dissipation, and the applicability of the mechanism to non-helical or electrode-free systems. By offering falsifiable predictions and reconciling theory with experimental raw data, this work aims to sharpen the dialogue surrounding the microscopic origin of CISS and stimulate further experimental and theoretical progress.
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All authors Subhajit Sarkar, Amos Sharoni, Oliver L. A. Monti, Yonatan Dubi