Quantum Gases
Anisotropic dispersion relation of ultralight Bose gases in modified Newtonian dynamics
Ning Liu
We investigate the dispersion relation of collective modes in ultralight Bose gases under Modified Newtonian Dynamics (MOND). Starting from the coupled Gross-Pitaevskii and MOND Poisson equations, we derive an anisotropic dispersion relation that depends on the angle between the perturbation wavevector and the background gravitational field. This anisotropy arises directly from the nonlinear structure of the MOND field equation and leads to a direction-dependent Jeans instability, with critical wavelengths and masses varying with orientation. Our results provide a distinctive signature of MOND in a
quantum astrophysical context and suggest that ultralight Bose gases can serve as novel probes of modified
gravity.
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Materials Science
Engineering of Orbital Hybridization: An Exotic Strategy to Manipulate Orbital Current
Kun Zheng, Haonan Wang, Ju Chen et al. (+17 more)
Current-induced
spin-orbit torque (SOT) plays a crucial role in the next-generation
spin-orbitronics. Enhancing its efficiency is both fundamentally and practically interesting and remains a challenge to date. Recently, orbital counterparts of
spin effects that do not rely on the
spin-orbit coupling (SOC) have been found as an alternative mechanism to realize it. This work highlights the engineering of copper oxidation states for manipulating the orbital current and its torque in the CuO$_x$-based
heterostructures. The orbital hybridization and thus the orbital-Rashba-Edelstein effect at the CuO$_x$/Cu interfaces are significantly enhanced by increasing the copper oxidation state, yielding a torque efficiency that is almost ten times larger than the conventional heavy metals. The Cu$_4$O$_3$/Cu interface, rather than the widely accepted CuO/Cu interface, is revealed to account for the enhanced SOT performance in the CuO$_x$-based
heterostructures. In addition, the torque efficiency can be alternatively switched between high and low thresholds through the redox reaction. The current results establish an exotic and robust strategy for engineering the orbital current and SOT for
spin-orbitronics, which applies to other weak-SOC materials.
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All authors Kun Zheng, Haonan Wang, Ju Chen, Hongxin Cui, Jing Meng, Zheng Li, Cuimei Cao, Haoyu Lin, Yuhao Wang, Keqi Xia, Jiahao Liu, Xiaoyu Feng, Hui Zhang, Bocheng Yu, Jiyuan Li, Yang Xu, Zhengzhong Yang, Shijing Gong, Qingfeng Zhan, Tian Shang
Statistical Mechanics
WH Statistics: Generalized Pauli Principle for Partially Distinguishable Particles
Wang Hao, Meng Yancen, Zhang Kuang et al. (+1 more)
Traditional statistical mechanics is constrained by the binary paradigms of identical/distinguishable and bosonic/fermionic particle statistics, leading to a fundamental logical gap in describing systems with partial distinguishability. We propose WH Statistics, a unified theoretical framework governed by three key parameters: continuous distinguishability {\lambda}, exclusion weight ąppa}, and intrinsic exclusivity {\gamma}. By deriving the microstate count and
entropy, we show that this framework naturally recovers the Bose-Einstein,
Fermi-Dirac, and Maxwell-Boltzmann statistics, while also incorporating anyons and the classical hard-core (Langmuir) limit. We introduce a class of generalized quasiparticles, termed WHons, which exhibit exotic physical phenomena including non-monotonic degeneracy pressure peaks, Schottky-like specific heat anomalies, and tunable interference effects, driven by the interplay between fractional distinguishability and exclusion. This framework bridges the century-old discontinuity between
quantum and classical exclusion principles, providing a powerful tool for investigating strongly correlated systems and programmable
quantum matter.
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All authors Wang Hao, Meng Yancen, Zhang Kuang, Zhou Rui'en
Materials Science · Cross-listed from physics.acc-ph
Development of next-generation light-weight ternary Mg–Al–Li alloys for beampipe applications in particle accelerators
Kamaljeet Singh, Kangkan Goswami, Raghunath Sahoo et al. (+1 more)
The current study reports the design of advanced light-weight materials for high-energy accelerator beampipe applications. The objective is to optimize the combined requirements of high radiation length and stiffness properties of the designed materials. The present study targets conventional beampipe materials such as aluminum, titanium, and stainless steel as primary performance
benchmarks. These conventional beampipes are used at synchrotron radiation sources, such as Indus-1 and Indus-2 in India, the Nuclotron-based Ion
Collider Facility in Russia, and the ring synchrotron facility SIS 100/300 at the Facility for Antiproton and Ion Research in Germany. In this context, a series of ternary Mg–Al–Li
alloys is systematically investigated to enhance the figure of merit. Two aluminum–rich
alloys, A1 ($\mathrm{Al_{61.5}Li_{10.8}Mg_{27.7}}$) and A2 ($\mathrm{Al_{66}Li_{19.4}Mg_{14.6}}$), along with three magnesium-rich
alloys, M1 ($\mathrm{Al_{23.9}Li_{29.3}Mg_{46.8}}$), M2 ($\mathrm{Al_{19}Li_{20.6}Mg_{60.4}}$), and M3 ($\mathrm{Al_{39.8}Li_{20.1}Mg_{40.1}}$) are explored. Thermodynamic stability, density, liquidus temperature, and phases are evaluated using Latin hypercube sampling within the Thermo-Calc TC-Python framework. Elastic properties are obtained from density functional theory calculations performed using the Vienna Ab Initio Simulation Package. Our results show that, although the elastic
moduli ($E$) of the investigated Mg-Al-Li
alloys are comparable to those of conventional beampipe materials, their significantly higher radiation lengths ($X_0$) lead to an overall improvement in the figure of merit $X_0 E^{1/3}$.
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All authors Kamaljeet Singh, Kangkan Goswami, Raghunath Sahoo, Sumanta Samal
Mesoscale and Nanoscale Physics
Monika E. Mycroft, Rostyslav O. Serha, Andrii V. Chumak et al. (+1 more)
We propose a method to prepare and certify Gaussian
quantum states of the
ferromagnetic resonance
spin-wave modes in ferromagnets using a longitudinal drive. Contrary to
quantum optics-based strategies, our approach harnesses a purely magnonic feature - the
spin-wave nonlinearity - to generate
magnon squeezing. This resource is used to prepare
vacuum-squeezed states, as well as entangled states between modes of different magnets coupled via a microwave cavity. We propose methods to detect such states with classical methods, such as
ferromagnetic resonance or local pickup coils, and quantify the required detection efficiency. We analytically solve the case of ellipsoidal yttrium iron garnet ferrimagnets, but our method applies to a vast range of shapes and sizes. Our work enables
quantum magnonics experiments without single-
magnon sources or detectors (
qubits), thus bringing the
quantum regime within reach of the wider magnonics community.
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All authors Monika E. Mycroft, Rostyslav O. Serha, Andrii V. Chumak, Carlos Gonzalez-Ballestero
Quantum Gases
Experimental study of magnetically insensitive transitions in ultracold Fermi gas of $^{40}$K
Biao Shan, Lianghui Huang, Yajing Yang et al. (+8 more)
This paper presents an experimental study of microwave single-
photon transitions that are
magnetic-field-insensitive in degenerate
Fermi gases of $^{40}$K. This contrasts with microwave single-
photon clock transitions for 0-0
magnetic-field-insensitive states and two-
photon clock transitions for non 0-0
magnetic-field-insensitive states in bosonic alkali metal atoms. We show that there are two sets of special transitions between two different hyperfine ground states ($|F$=9/2, $m_{F}$=1/2$\rangle$ $\Leftrightarrow$ $|$7/2, -1/2$\rangle$ and $|$9/2, -1/2$\rangle$ $\Leftrightarrow$ $|$7/2, 1/2$\rangle$), whose microwave single-
photon transition frequency is insensitive to low
magnetic fields, as the first-order Zeeman shift is almost completely canceled. By using the microwave spectrum and Ramsey interference fringes, we demonstrate the long-time stability of the coherent transition under
magnetic field fluctuations. These
magnetic-field-insensitive microwave hyperfine transitions in ultracold $^{40}$K
Fermi gases offer promising applications in
quantum information and precision measurements.
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All authors Biao Shan, Lianghui Huang, Yajing Yang, Yuhang Zhao, Jiahui Shen, Zhuxiong Ye, Liangchao Chen, Zengming Meng, Pengjun Wang, Wei Han, Jing Zhang
Mesoscale and Nanoscale Physics
Sang-Hoon Han, Jun-Won Rhim and Chang-geun Oh
Klein tunneling stands as a fundamental probe of relativistic
quantum transport in two-dimensional materials. We investigate this phenomenon in quadratic band-touching systems, where the
Hilbert-Schmidt
quantum distance plays a central role in the underlying mechanism. By employing a generic
parabolic model, we systematically disentangle the cooperative effects of intrinsic mass asymmetry and tunable
quantum geometry. We demonstrate that mass asymmetry sets the overall transmission profile, including the angular distribution and the resonance channels. In contrast, we show that
quantum geometry provides a universal parameter that modulates tunneling efficiency by tuning the
quantum distance, while leaving the energy dispersion unchanged. Specifically,
quantum geometry plays a dual role: it governs the overall transmission amplitude through pseudospin mismatch, while its interplay with Fabry-Perot interference induces observable shifts in resonance angles. Our findings reveal that incorporating
quantum geometry alongside band structure is essential for a complete description of
quantum transport.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Connecting Magic Dynamics in Thermofield Double States to Spectral Form Factors
Ning Sun and Pengfei Zhang
Under
unitary evolution, chaotic
quantum systems initialized in simple states rapidly develop high complexity, precluding any efficient classical description.
Quantum chaos is traditionally characterized by spectral properties of the
Hamiltonian, most notably through the spectral form factor, while the hardness of classical simulation within the stabilizer formalism, commonly referred to as
quantum magic, can be quantified by the stabilizer Rényi
entropy. In this Letter, we propose a relation between the dynamics of the stabilizer Rényi
entropy for thermofield double states and the spectral form factor, based on general arguments for chaotic systems with all-to-all interactions. This relation implies that the saturation of the stabilizer Rényi
entropy is governed by a first-order dynamical transition. We then demonstrate this relation explicitly in the Sachdev-Ye-Kitaev model, using an auxiliary-
spin representation of the stabilizer Rényi
entropy that exhibits an emergent $Z_2$
symmetry. We further find that, in the high-temperature regime of the SYK model, the transition occurs at a finite time, with the long-time phase marked by spontaneous $Z_2$
symmetry breaking. In contrast, at low temperatures, the transition is pushed to times exponentially long in the system size. Our results reveal an intriguing interplay between
quantum chaos and
quantum magic.
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Quantum Gases
Quantum droplets in a resonant Bose-Fermi mixture
Sam Foster, Olivier Bleu, Jesper Levinsen et al. (+1 more)
We study the canonical problem of a
Fermi gas interacting with a weakly repulsive Bose-Einstein condensate at zero temperature. To explore the
quantum phases across the full range of
boson-
fermion interactions, we construct a versatile variational ansatz that incorporates pair correlations and correctly captures the different polaron limits. Remarkably, we find that self-bound
quantum droplets can exist in the strongly interacting regime, preempting the formation of
boson-
fermion dimers, when the
Fermi pressure is balanced by the resonant
boson-
fermion attraction. This scenario can be achieved in experimentally available Bose-
Fermi mixtures for a range of
boson-
fermion mass ratios in the vicinity of equal masses. We furthermore show that a larger
fermion density instead yields phase separation between a Bose-
Fermi mixture and excess
fermions, as well as behavior reminiscent of a
liquid-gas critical point. Our results suggest that first-order
quantum phase transitions play a crucial role in the phase diagram of Bose-
Fermi mixtures.
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All authors Sam Foster, Olivier Bleu, Jesper Levinsen, Meera M. Parish
Materials Science
Inverse Chiral Phonon Zeeman Effect in Noncentrosymmetric Crystals
Jun-ichiro Kishine, A. S. Ovchinnikov, Masahiro Sato et al. (+2 more)
We present a quantized effective theory of the inverse
chiral phonon Zeeman effect in noncentrosymmetric
crystals. Within micropolar elasticity, coupled translational displacements and microrotations give rise to intrinsically
chiral phonons, which generate an elliptically polarized internal
magnetic field through dynamical piezoelectricity. Provided that electronic screening is incomplete, this field acts as an effective longitudinal Zeeman field on electronic
spins, driving a Floquet response for localized states and a stationary adiabatic band splitting for itinerant electrons, leading to macroscopic
spin polarization. In contrast to earlier discussions based on nearly degenerate axial optical modes or externally driven circular
lattice motion, the present mechanism relies on finite-wave-number truly
chiral phonons whose counter-rotating branches are intrinsically split by
crystal chirality. Quantization is introduced to define the single-
phonon magnetic-field scale, coherent-state enhancement, and
magnetic chirality in a controlled manner. The results establish a purely
lattice-driven mechanism for the inverse
chiral phonon Zeeman effect in noncentrosymmetric
crystals.
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All authors Jun-ichiro Kishine, A. S. Ovchinnikov, Masahiro Sato, G. N. Makarov, A. D. Lyakhov
Materials Science
Room temperature intrinsic anomalous Hall effect in disordered half-metallic ferromagnetic quaternary Heusler alloy CoRuFeSi
Manikantha Panda, Sonali S. Pradhan, Prabuddha Kant Mishra et al. (+6 more)
Quaternary Heusler
alloys offer a versatile platform for engineering
magnetic and topological transport phenomena through chemical flexibility and tunable disorder. Here, we report a comprehensive experimental and theoretical investigation of the
magnetic, magnetotransport, and anomalous
Hall properties of the quaternary Heusler
alloy CoRuFeSi. The compound crystallizes in the LiMgPdSn-type structure with significant Co–Ru antisite disorder and exhibits soft ferromagnetism with a saturation magnetization of $4.21~\mu_{\mathrm{B}}/\mathrm{f.u.}$ at low temperature and a Curie temperature well above room temperature.
Hall measurements reveal a robust anomalous
Hall effect persisting up to 300~K, with an anomalous
Hall conductivity of $\sim 74$~S/cm that is nearly temperature independent. Scaling analysis demonstrates that the anomalous
Hall response is dominated by the intrinsic Berry-
curvature mechanism. First-principles calculations identify CoRuFeSi as a topologically nontrivial nodal-line semimetal in its ordered phase. Incorporation of experimentally relevant Co–Ru antisite disorder redistributes the Berry
curvature and quantitatively reproduces the experimentally observed anomalous
Hall conductivity, while preserving half-
metallicity. These results establish CoRuFeSi as a disorder-tolerant half-metallic ferromagnet with a sizable intrinsic anomalous
Hall effect at room temperature, highlighting its potential for spintronic and
Hall-based device applications.
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All authors Manikantha Panda, Sonali S. Pradhan, Prabuddha Kant Mishra, Alapan Bera, Rosni Roy, Rajib Mondal, Soumik Mukhopadhyay, V. Kanchana, Tapas Paramanik
Superconductivity
Unusual antiferromagnetic order and fluctuations in RbMn$_{6}$Bi$_{5}$
Chao Mu, Long Chen, Jiabin Song et al. (+5 more)
Quasi-one-dimensional RbMn$_{6}$Bi$_{5}$, the first pressure-induced ternary Mn-based
superconductor, exhibits a phase diagram analogous to those of cuprate and iron-based
superconductors, with superconductivity neighboring
antiferromagnetic order. Here, we use $^{55}$Mn and $^{87}$Rb
nuclear magnetic resonance (NMR) to unravel its
magnetic structure and fluctuations. Above the Néel temperature ($T_{\rm N}$), strong
antiferromagnetic fluctuations dominate, characteristic of a paramagnetic state with pronounced
spin-
lattice relaxation rate enhancement. Below $T_{\rm N}$, a first-order phase transition establishes a commensurate
antiferromagnetic order, where Mn atoms at the pentagon corners exhibit distinct
magnetic moments with different orientations, while the central Mn atom carries no
magnetic moment. The complex
magnetic architecture, revealed by zero-field and high-
magnetic-field NMR spectra, contrasts with earlier
neutron diffraction models proposing uniform
spin density waves, instead supporting localized moments ordering with charge rearrangement. The proximity of robust
antiferromagnetic fluctuations to the high-pressure superconducting phase suggests a potential role for
magnetic excitations in mediating unconventional Cooper pairing, akin to paradigmatic high-$T_c$ systems. These findings provide critical insights into the interplay between
geometric frustration,
magnetic order, and superconductivity in manganese-based materials.
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All authors Chao Mu, Long Chen, Jiabin Song, Wei Wu, Gang Wang, Jinguang Cheng, Zheng Li, Jianlin Luo
Materials Science
Lithium and sodium decorated PHE-graphene for high capacity hydrogen storage: A DFT and GCMC study
Hongyan Ma, Qing Wang, Huilin Sun et al. (+5 more)
Porous nanocarbon materials are seen as potential excellent materials for hydrogen storage due to their high surface area, excellent cycling stability and favorable kinetics. This study employs Density Functional Theory (DFT) simulations to investigate key property of Li$^-$ and Na$^-$ modified PHE-
graphene, including structural stability, electronic properties, and hydrogen storage capabilities. The results show that when each Li atom adsorbs six hydrogen molecules, the material reaches the maximum hydrogen adsorption gravimetric density of 15.20 wt%. Additionally, through Grand Canonical Monte Carlo (GCMC) simulations, we obtained the hydrogen weight ratios and adsorption enthalpy curves for Li- and Na-modified PHE under varying temperature and pressure conditions. These findings indicate that both Li- and Na-modified PHE-
graphene are exceptional candidates for hydrogen storage materials, particularly in mobile applications.
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All authors Hongyan Ma, Qing Wang, Huilin Sun, Qingyu Li, Yunhui Wang, Zhihong Yang, Huaihong Zhao, Huazhong Shu
Materials Science
Quantum theory of elastic strings and the thermal conductivity of glasses
Fernando Lund and Bruno Scheihing-Hitschfeld
We study the thermal conductivity of amorphous solids by constructing a continuum model whose degrees of freedom are propagating vibrational modes (
phonons) and extended Volterra dislocation line defects with their own vibrational degrees of freedom which do not propagate in space. Our working assumption is that these additional degrees of freedom account for the "
boson peak" that is observed in glassy materials. This identification allows us to obtain the length distribution of dislocations from experimental data of the
boson peak for each material, which we use as input to calculate the
phonon self-energy in a
quantum field theory framework using that the
phonon-dislocation interaction is given by the Peach-Koehler force. The tail of the distribution for long dislocations is consistent with an $L^{-5}$ power law. Our results show that this power law yields a linear rise in the thermal conductivity, as observed in glasses at low temperatures. We then consider two approaches to describe thermal conductivity data quantitatively. In the simplest approach we only keep the low-frequency behavior of the
phonon self-energy with one free parameter, plus an adjustable UV cutoff. In the more realistic approach we keep the full frequency dependence of the
phonon self-energy as dictated by the
phonon-dislocation interaction plus an additional contribution due to scattering with point defects, with a cutoff set by the typical interatomic spacing of the material. We obtain a satisfactory description of thermal conductivity data with both approaches. We conclude by discussing prospects to test the predictive power of this model.
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Disordered Systems and Neural Networks · Cross-listed from q-bio.PE
Energy flow controls the stability of multitrophic ecosystems with stratified nonreciprocity
Rukmani Ramachandran and Akshit Goyal
Complex systems with nonreciprocal interactions are often stratified into layers. Ecosystems are a
prime example, where species at one trophic level grow by consuming those at another. Yet the dynamical consequences of such stratified nonreciprocity – where the correlation between growth and consumption differs across trophic levels – remain unexplored. Here, using an ecological model with three trophic levels, we reveal an emergent asymmetry: nonreciprocal interactions between consumers and predators (top and middle level) destabilize ecosystems far more readily than nonreciprocity between consumers and resources (middle and bottom level). We analytically derive the phase diagram for the model and show that its stability boundary is controlled by energy flow across trophic levels. Because energy flows upward – from resources to predators – diversity is progressively lower at higher trophic levels, which we show explains the asymmetry. Lowering energy flow efficiency flips the asymmetry toward resources and remarkably expands the stable region of the phase diagram, suggesting that the famous "10% energy transfer" seen in natural ecosystems might promote stability. More broadly, our findings show that the location of nonreciprocity within a complex network, not merely its magnitude, determines stability.
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Strongly Correlated Electrons
Self-Consistent Coulomb Interactions from Constrained Dynamical Mean-Field Theory
Antik Sihi, Subhasish Mandal and Kristjan Haule
We develop a self-consistent first-principles framework for determining the screened Coulomb interaction strength (U) based on constrained dynamical mean-field theory (cDMFT). Unlike conventional approaches, this method incorporates essential vertex corrections within the same embedded-DMFT formalism used for the electronic structure calculation. Using the cDMFT-derived interaction strengths as input to embedded DMFT yields spectral functions in excellent agreement with photoemission experiments across a wide range of materials, spanning 3d to 5d transition-metal compounds, including correlated metals, Mott
insulators, altermagnets, and unconventional
superconductors. This unified many-body framework establishes a systematic first-principles route for determining interaction strengths in correlated materials and substantially enhances the predictive power of DFT+DMFT and its extensions.
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Superconductivity
Correlation between superfluid density and transition temperature in infinite-layer nickelate superconductor $Nd_{1-x}Sr_xNiO_2$
Z. J. Li, R .Z. Zhang, M. H. Xu et al. (+10 more)
A strong correlation between zero-temperature superfluid density ($\rho_{s0}$) and transition temperature ($T_c$) is considered as a hallmark of unconventional superconductivity. However, their relationship has yet to be unveiled in nickelates due to sample inhomogeneity. Here we perform local susceptometry on an infinite-layer nickelate
superconductor $Nd_{0.8}Sr_{0.2}NiO_2$. The sample shows inhomogeneous superfluid density and $T_c$ on micron-scale. The spatial statistics for different scan areas reveal a linear dependence of local $T_c$ on $\rho_{s0}$ for $T_c$>8 K and a sub-linear one for $T_c$<8 K. Remarkably, the overall relationship is reminiscent of that reported in overdoped cuprate
superconductors, hinting at a close connection between them.
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All authors Z. J. Li, R .Z. Zhang, M. H. Xu, K. Y. Liang, Y. Zhao, Q. S. He, Q. Z. Zhou, B. R. Chen, P. H. Zhang, K. Z. Yao, H. X. Yao, L. Qiao, Y. H. Wang
Materials Science · Cross-listed from physics.optics
Purely equatorial lasing in spherical liquid crystal polymer microlasers with bipolar refractive index profile
David Ripp, Nachiket Pathak, Vera M. Titze et al. (+3 more)
Liquid crystal whispering gallery mode (WGM) microlasers show high sensitivity to external stimuli and distinct spectral features, rendering them ideally suited for various sensing applications. They also offer intrinsic anisotropic optical properties, which can be used to shape and manipulate light even inside spatially highly symmetric structures. Here, we report the fabrication of a spherical bipolar
liquid crystal polymer microlaser that tightly confines the optical path of WGMs to the equatorial plane. By controlled anchoring of the
liquid crystal mesogens followed by polymerization, a fixed refractive index profile is formed within the spherical microcavity. Consequently, only transverse electric (TE) modes oscillating in the equatorial plane experience the high extraordinary refractive index, allowing to confine lasing into a single plane. Furthermore, we observe a characteristic splitting into sub-modes. By combining hyperspectral imaging, optical modeling, and theoretical calculations, we show that the observed sub-modes originate from the lifting of the energy degeneracy of azimuthal WGMs. The unique ability to confine lasing into a single plane makes these spherical microlasers independent of the exact position of the pump beam, which allows consistent localized sensing especially in combination with fast point scanning microscopes or inside highly dynamic biological environments.
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All authors David Ripp, Nachiket Pathak, Vera M. Titze, Catriona A. Thomson, Andreas Mischok, Marcel Schubert
Mesoscale and Nanoscale Physics
Kineo-Elasticity and Nonreciprocal Phonons by Rashba-induced Interfacial Spin-Lattice Coupling
Gyungchoon Go and Se Kwon Kim
We identify a previously unrecognized
spin-
lattice coupling allowed by broken inversion
symmetry that can be viewed as a
lattice analogue of electronic Rashba
spin-orbit coupling. In the low-frequency regime, where
magnons are integrated out, its interplay with the conventional magnetoelastic coupling generates a kineo-elastic term that couples strain and
lattice velocity, giving rise to nonreciprocal
phonon velocity. We further analyze the full
magnon-
phonon spectrum and find that the competition between interfacial
spin-
lattice and magnetoelastic couplings leads to directional hybridization and absorption, yielding asymmetric
phonon propagation lengths for opposite directions. Our results indicate that such interfacial
spin-
lattice coupling can provide an efficient route to nonreciprocal
phonon propagation in
magnetic heterostructures with strong Rashba
spin-orbit coupling.
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Materials Science
3D atomistic imaging of polymer nanocomposites with Atom Probe Tomography: experimental methodology, preliminary results and future outlook
James O. Douglas, Reza Salehiyan, Aparna Saksena et al. (+5 more)
The use of
polymer nanocomposites as gas barrier materials has seen increasing interest, including applications involving hydrogen transport and storage. Better understanding of gas transport through those polymeric systems requires 3D nanoscale detection of distributions and the possible trapping of gas molecules within nanoparticles and
polymer/nanoparticle interfaces While atom probe
tomography (APT) offers promising means for such nanoscale characterisation, its use for
polymers has been mainly limited to thin organic layers deposited onto substrates or pre-fabricated metal needle shaped specimens. This work provides the very first application of APT to bulk
polymer nanocomposites. Particularly, site specific atom probe sample preparation by Focused Ion Beam (FIB) liftout has been shown for the first time in a model system of hexagonal boron nanoparticles within a PVDF
polymer matrix, using a variety of FIB workflows including Xe FIB, Ga FIB, cryogenic Ga FIB and deuterium charging. Mass spectra from the bulk
polymer and the nanoparticle were collected using pulsed
laser atom probe using standard conditions and compared. Several challenges encountered during this research including damage of the polymeric
matrix during sample preparation were extensively discussed in this paper. Once those challenges have been resolved (e.g. by developing site specific sample preparation protocols), the application of APT to
polymer nanocomposites can open new options for nanoscale characterisation of those systems.
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All authors James O. Douglas, Reza Salehiyan, Aparna Saksena, Tim M. Schwarz, Baptiste Gault, Stella Pedrazzini, Emilio Martinez-Paneda, Łukasz Figiel
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Inertia-Dilatancy Interplay Governs Shear-Thickening Drop Impact
Anahita Mobaseri, Leonardo Gordillo, Charles Burton et al. (+5 more)
Combining high-speed photography with direct force measurements, we investigate the impact dynamics of drops of cornstarch-water mixtures – a premier example of shear-thickening fluids – across a wide range of impact conditions. Our study identifies three distinct impact regimes. In addition to the
liquid-like and solid-like behaviors generally expected for the impact-induced response of shear-thickening fluids, we uncover a counterintuitive regime in which high-concentration cornstarch-water mixtures display a
liquid-like response at the onset of impact when shear rates are high and only transition to a solid-like behavior at later times as shear rates reduce. By integrating the classic drop-impact theory with the Reynolds-Darcy mechanism for dilatancy, we develop a unified model that quantitatively describes the impact dynamics of shear-thickening drops across all regimes. Our work reveals the unexpected response of shear-thickening fluids to ultra-fast deformation and advances fundamental understanding of drop impact for complex fluids.
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All authors Anahita Mobaseri, Leonardo Gordillo, Charles Burton, Soyoon Yoon, Dong Lee, Satish Kumar, Michelle M. Driscoll, Xiang Cheng
Materials Science · Cross-listed from physics.chem-ph
Enhanced Climbing Image Nudged Elastic Band method with Hessian Eigenmode Alignment
Rohit Goswami, Miha Gunde and Hannes Jónsson
Accurate determination of transition states is central to an understanding of reaction kinetics. Double-endpoint methods where both initial and final states are specified, such as the climbing image nudged elastic band (CI-NEB), identify the minimum energy path between the two and thereby the saddle point on the energy surface that is relevant for the given transition, thus providing an estimate of the transition state within the harmonic approximation of transition state theory. Such calculations can, however, incur high computational costs and may suffer stagnation on exceptionally flat or rough energy surfaces. Conversely, methods that only require specification of an initial set of atomic coordinates, such as the minimum mode following (MMF) method, offer efficiency but can converge on saddle points that are not relevant for transition of interest. Here, we present an adaptive hybrid
algorithm that integrates the CI-NEB with the MMF method so as to get faster convergence to the relevant saddle point. The method is benchmarked for the Baker-Chan (BC) saddle point test set using the PET-MAD machine-learned potential as well as 59 transitions of a heptamer island on Pt(111) from the OptBench
benchmark set. A
Bayesian analysis of the performance shows a reduction in energy and force calculations of 57% [95% CrI: -64%, -50%] relative to CI-NEB for the BC set, while a 31% mean reduction is found for the transitions of the heptamer island. These results establish this hybrid method as a highly effective tool for high-throughput automated chemical discovery of atomic rearrangements.
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