Materials Science
Unveiling the amorphous ice layer during premelting using AFM integrating machine learning
Binze Tang, Chon-Hei Lo, Tiancheng Liang et al. (+6 more)
Premelting plays a key role across physics, chemistry, materials and biology sciences but remains poorly understood at the atomic level due to surface characterization limitations. We report the discovery of a novel amorphous ice layer (AIL) preceding the quasi-
liquid layer (QLL) during ice premelting, enabled by a machine learning framework integrating atomic force microscopy (AFM) with molecular dynamics simulations. This approach overcomes AFM's depth and signal limitations, allowing for three-dimensional surface structure reconstruction from AFM images. It further enables structural exploration of premelting interfaces across a wide temperature range that are experimentally inaccessible. We identify the AIL, present between 121-180K, displaying disordered two-dimensional hydrogen-bond network with solid-like dynamics. Our findings refine the ice premelting phase diagram and offering new insights into the surface growth dynamic, dissolution and interfacial chemical reactivity. Methodologically, this work establishes a novel framework for AFM-based 3D structural discovery, marking a significant leap in our ability to probe complex disordered interfaces with unprecedented precision and paving the way for future disciplinary research, including surface reconstruction, crystallization, ion solvation, and biomolecular recognition.
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All authors Binze Tang, Chon-Hei Lo, Tiancheng Liang, Jiani Hong, Mian Qin, Yizhi Song, Duanyun Cao, Ying Jiang, Limei Xu
Strongly Correlated Electrons
Symmetry classification of magnetic octupole current based on multipole representation theory
Yuuga Takasu and Satoru Hayami
Magnetic octupole (MO) currents have recently attracted significant
attention as a driving force for the Neel vector dynamics in d-wave altermagnets, a new class of antiferromagnets that exhibit nonrelativistic
spin-split band structures. From a
symmetry perspective, the MO includes an axial-dipole component analogous to that of the
spin, making it essential to clarify how MO currents differ from
spin currents. We here investigate the correspondence between MO conductivities and electronic multipoles, which provide a unified and powerful framework for
symmetry analysis. We derive the multipole representation of the rank-five MO conductivity tensor and classify its
symmetry-allowed components for all crystallographic point groups, in direct comparison with
spin conductivity. We show that time-reversal-even electric-type multipoles give rise to the dissipationless MO current, whereas time-reversal-odd
magnetic-type multipoles generate dissipative MO current under an applied electric field. Complementing this macroscopic analysis, the linear-response calculations for a microscopic tight-binding model demonstrate how MO conductivities are activated by
symmetry lowering, exemplified by the
symmetry reduction from Oh to Th. Our results elucidate the
symmetry distinctions between MO currents and
spin currents, and provide insights into their experimental identification.
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Materials Science
Many-Body Correlation Effects in Fröhlich Electron-Phonon Coupling
Zien Zhu, Chih-En Hsu, Benran Zhang et al. (+5 more)
In compound
semiconductors and
insulators, the polar electron-
phonon coupling diverges at long range, known as the Fröhlich interaction. Modern first-principles electron-
phonon calculations treat the Fröhlich interaction in a semiclassical electrostatic formalism based on density-functional perturbation theory. Here, using many-body $GW$ perturbation theory, we reveal important electron correlation effects in the Fröhlich-type electron-
phonon coupling, which are missed by the prevailing approaches and rooted in the fundamentally distinct behavior between quasiparticle self-energy and semi-local exchange-correlation functionals in the long-range limit. Going beyond the electrostatic treatment, we derive and implement the $GW$ self-energy contribution to the long-range polar electron-
phonon coupling, and demonstrate its critical role and nontrivial behaviors in properties such as electron linewidth and polaron formation in several prototype
semiconductors. Remarkably, calculations on photoemission kink in electron-doped TiO$_2$ achieve excellent agreement with experiment. Our work establishes the many-body generalization of the Fröhlich interaction that is essential for accurate electron-
phonon calculations at the full $GW$ level combined with Wannier interpolation techniques.
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All authors Zien Zhu, Chih-En Hsu, Benran Zhang, Zhenfa Zheng, Mauro Del Ben, Antonios M. Alvertis, Hung-Chung Hsueh, Zhenglu Li
Mesoscale and Nanoscale Physics
Tuning molecular thermal conductance through endgroup modification and halogen substitution
Jonathan J. Wang and Dvira Segal
We demonstrate tuning of the phononic thermal conductance in single molecules with carbon-chain backbones through modifications of terminal groups and halogen substitution of hydrogen atoms. Our simulations focus on intrinsic molecular properties, and we employ a workflow based on ab initio molecular dynamics, enabling the training and development of machine-learned interatomic potentials. These potentials are subsequently used in classical nonequilibrium molecular dynamics simulations to extract thermal conductance coefficients. Replacing terminal methyl groups with amine, sulfur, or halogen substituents leads to pronounced changes in thermal conductance: bromine-terminated chains exhibit the lowest conductance, whereas amine and methyl-terminated chains show the highest. Additionally, single-atom substitution of hydrogen by fluorine or other halogens along the alkane backbone significantly reduces thermal transport. Finally, our simulations of the length dependence of thermal conductance in alkane chains containing 3-12 carbon atoms reveal its saturation beyond eight carbon atoms. Together, our findings show that simple chemical modifications offer a versatile route to controlling phononic heat flow in single molecules.
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Strongly Correlated Electrons
Substrate tuning of the structural and electronic transition in thin flakes of the excitonic insulator candidate Ta$_2$NiSe$_5$
Yuan-Shan Zhang, Zichen Yang, Chuanlian Xiao et al. (+4 more)
Ta$_2$NiSe$_5$ continues to draw interest for its $T_\textrm{c}$ = 326 K phase transition, whose dual electronic and structural nature reflects a complex interplay of electron-hole (excitonic) and electron-
lattice interactions. The majority of studies that have attempted to decipher the relative importance of these interactions, particularly through charge tuning, have been focused on bulk samples. Here, we utilize an all-dry exfoliation and transfer protocol to isolate ultrathin flakes of Ta$_2$NiSe$_5$ on insulating Al$_2$O$_3$ and conducting Au. Using polarized Raman spectroscopy, we uncover the following substrate dependence: Four layers of Ta$_2$NiSe$_5$ on Al$_2$O$_3$ show a sharp structural and electronic transition that is lowered by roughly 40 K from the bulk $T_\textrm{c}$. Meanwhile, four layers of Ta$_2$NiSe$_5$ on Au undergo a structural and electronic transition that is much more gradual with respect to temperature and finishes roughly 150 K below the bulk $T_\textrm{c}$. The pronounced broadening points to an atomic-scale interface effect, wherein electrostatic screening and charge transfer from Au produces a $T_\textrm{c}$ gradient perpendicular to the layers of the flake. We discuss the role of excitonic physics and suggest the possibility for interface engineering to pattern nanoscale junctions in Ta$_2$NiSe$_5$.
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All authors Yuan-Shan Zhang, Zichen Yang, Chuanlian Xiao, Masahiko Isobe, Matteo Minola, Hidenori Takagi, Dennis Huang
Materials Science · Cross-listed from physics.chem-ph
A Software Package for Generating Robust and Accurate Potentials using the Moment Tensor Potential Framework
Josiah Roberts, Biswas Rijal, Simon Divilov et al. (+6 more)
We present the Plan for Robust and Accurate Potentials (PRAPs), a software package for training and using moment tensor potentials (MTPs) in concert with the Machine Learned Interatomic Potentials (MLIP) software package. PRAPs provides an automated workflow to train MTPs using active learning procedures, and a variety of utilities to ease and improve workflows when utilizing the MLIP software. PRAPs was originally developed in the context of
crystal structure prediction, in which one calculates convex hulls and predicts low energy metastable and thermodynamically stable structures, but the potentials PRAPs develops are not limited to such applications. PRAPs produces two potentials, one capable of rough estimates of the energies, forces and stresses of almost any chemical structure in the specified compositional space – the Robust Potential – and a second potential intended to provide more accurate descriptions of ground state and metastable structures – the Accurate Potential. We also present a Python library, mliputils, designed to assist users in working with the chemical structural files used by the MLIP package.
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All authors Josiah Roberts, Biswas Rijal, Simon Divilov, Jon-Paul Maria, William G. Fahrenholtz, Douglas E. Wolfe, Donald W. Brenner, Stefano Curtarolo, Eva Zurek
Strongly Correlated Electrons · Cross-listed from hep-th
Complete Topological Quantization of Higher Gauge Fields
Hisham Sati and Urs Schreiber
After global completion of higher gauge fields (as appearing in higher-dimensional supergravity) by proper flux quantization in extraordinary nonabelian
cohomology, the (non-perturbative, renormalized) topological
quantum observables and
quantum states of solitonic field histories are completely determined through a topological form of light-front quantization. We survey the logic of this construction and expand on aspects of the quantization argument. In the instructive example of 5D Maxwell-Chern-Simons theory (the gauge sector of 5D SuGra) dimensionally reduced to 3D, a suitable choice of flux quantization in Cohomotopy ("Hypothesis h") recovers this way the fine detail of the traditionally renormalized (Wilson loop)
quantum observables of abelian Chern-Simons theory and makes novel predictions about anyons in fractional
quantum (anomalous)
Hall systems. An analogous choice ("Hypothesis H") of global completion of 11D higher Maxwell-Chern-Simons theory (the higher gauge sector of 11D SuGra) realizes various aspects of the topological sector of the conjectural "M-theory" and its M5-branes.
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Soft Condensed Matter
Field-Particle Interactions in Curved Flows for Shape-Asymmetric Active Particles
Derek C. Gomes and Tapan C. Adhyapak
We show that
curvatures in general ambient flow profiles can align shape-asymmetric active particles, revealing a previously overlooked competition with externally applied aligning fields. Focusing on the ubiquitous case of channel flows, we then investigate the fundamental consequences of this competition for the dynamics of shape-asymmetric active particles in microchannels in the presence of orienting fields. We find that this interplay gives rise to novel mechanisms for controlling particle dynamics, with potentially broad applications, and suggests exciting possibilities such as active-particle analogs of electronic systems.
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Materials Science
Rational Design Principles for Na- and Li-ion Carbon Anodes from Interlayer Spacing Control
Ihor Radchenko and Oleksandr I. Malyi
Graphite, the standard commercial anode for Li-ion batteries, is thermodynamically incompatible with Na-ion batteries, leading researchers to search for alternative C-based structures (e.g., hard carbon, expanded graphite). In a simplified picture, the main idea of such search relies on identifying disordered C structures with a large interlayer spacing and distribution of local structural motifs (e.g., pores) with target electrochemical properties. Such exploration is typically done via trial-and-error experimentation, which often does not allow precise understanding of the role of interlayer distance and even Na/Li-ion intercalation in the electrochemical performance. Motivated by this, using density-functional theory and cluster expansion, we establish a structure-property relationship for Li- and Na-intercalation across a range of graphite interlayer spacings and stacking arrangements. We show that Na intercalation becomes thermodynamically possible in large concentrations above 4.21 Å even without a change in interlayer spacing. Conversely, Li intercalation has a narrow optimal window, with maximum capacity (close to the commercial limit) at approximately 3.75 Å, while larger spacings (e.g., 4.58 Å) quickly reduce Li storage capacity. We also find that AA-stacked domains consistently offer stronger ion bonding and higher voltages than AB-stacked domains for both ions. Our results, thus, not only explain the role of metal ion intercalation in the electrochemical performance, but also clarify the fundamental design trade-offs for expanded C anodes, offering practical targets and interlayer distance ranges for the independent optimization of the next generation of negative electrodes for metal-ion batteries.
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Soft Condensed Matter
Exploring the energy landscape of the logarithmic potential: local minima and stationary states
Paolo Amore, Victor Figueroa and Raymundo Ramos
We have performed a detailed exploration of the energy landscape for configurations of points on the sphere, interacting via the logarithmic potential, and corresponding to local minima of the total energy, up to $N = 160$. The growth of $N_{\rm conf}$ (number of distinct configurations) is exponential, as for the Thomson problem, although weaker. Using the techniques described in our previous paper~\cite{Amore25} we have also explored the solution landscape of this problem for $N \leq 24$, and found that the number of stationary states is growing exponentially.
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Soft Condensed Matter
Morphogenesis of bacterial colonies in liquid crystalline environments
Sebastian Gonzalez La Corte, Thomas G. J. Chandler, Saverio E. Spagnolie et al. (+2 more)
Natural bacterial habitats are often complex fluids with viscoelastic and anisotropic responses to stress; for example, they can take the form of
liquid crystals (LCs), with elongated microscopic constituents that collectively align while still retaining the ability to flow. However, laboratory studies typically focus on
cells in simple
liquids or complex fluids with randomly-oriented constituents. Here, we show how interactions with LCs shape bacterial proliferation in multicellular colonies. Using experiments, we find that in a nematic LC,
cells generically form aligned single-
cell-wide "chains" as they reproduce. As these chains lengthen, they eventually buckle in a highly localized manner. By combining our measurements with a continuum mechanical theory, we demonstrate that this distinctive morphogenetic program emerges because
cells are kept in
alignment due to the LC's elasticity; as each chain lengthens, growth-induced viscous stresses along its contour eventually overcome the elasticity of the surrounding nematic, leading to buckling. Our work thus reveals and provides mechanistic insight into the previously-overlooked role of LCs in sculpting bacterial life in complex environments.
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All authors Sebastian Gonzalez La Corte, Thomas G. J. Chandler, Saverio E. Spagnolie, Ned S. Wingreen, Sujit S. Datta
Strongly Correlated Electrons
Diagrammatics in the Dual Space, or There and Back Again
Evgeny A. Stepanov
Accurately describing many-body effects in multi-orbital systems remains a major challenge in theoretical condensed matter physics. At present, there is a significant methodological gap between the numerical tools used in ab initio computational materials science and those developed to study strong electronic correlations. The former can treat realistic, large-scale systems but typically neglect many-body effects, while the latter focus on simplified models with only a few degrees of freedom, as only such models can be solved accurately in the presence of strong interactions. The purpose of this thesis is to bridge these two approaches and establish a systematic theoretical framework for realistic correlated electronic materials. This involves a full-cycle methodology that begins with constructing ab initio interacting models from density-functional theory, solving them using dynamical mean-field theory to capture local correlations, and extending beyond to incorporate non-local collective electronic fluctuations. To this end, we introduce the "dual" approach to strong correlations, which includes the dual
fermion, dual
boson, and dual triply irreducible local expansion methods. The central idea of the dual theories is to shift the reference point of the conventional Feynman diagrammatic expansion from a non-interacting electronic system to an interacting but exactly solvable one. Integrating out this reference system recasts the expansion in an effective dual space, where all diagrammatic building blocks are renormalized by the corresponding
impurity quantities. This procedure transforms a non-perturbative expansion in the original variables into a perturbative expansion in terms of dual fermionic and bosonic fields, exact in both the weak- and strong-coupling limits. In this thesis, we collect and systematize the major developments of dual techniques achieved to date.
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Soft Condensed Matter
Soft Colloidal Robots: Magnetically Guided Liquid Crystal Torons for Targeted Micro-Cargo Delivery
Joel Torres, Rodrigo C.V. Coelho, Patrick Oswald et al. (+2 more)
Quasiparticles in
liquid crystals, such as torons and skyrmions, represent a new class of topologically protected solitonic excitations, offering a promising route toward soft microrobotics. Here we demonstrate that torons can be propelled by modulated electric fields and magnetically steered with full directional control, thus achieving programmable trajectories without net
liquid flow. Within microfluidic architectures, we guide ensembles of torons through confined channels and realize targeted pick-up, transport, and release of colloidal cargo. By combining experiments and numerical simulations, we uncover how
magnetic alignment reshapes toron structure, speed, and stability, while confinement within microchannels gives rise to novel transport regimes. Unlike conventional colloidal inclusions, torons are intrinsically uniform, soft, and reconfigurable, establishing them as both an ideal model system for studying emergent phenomena in active topological matter and a versatile platform for next-generation soft
robots, adaptive delivery systems, and smart active matter.
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All authors Joel Torres, Rodrigo C.V. Coelho, Patrick Oswald, Francesc Sagés, Jordi Ignés-Mullol
Quantum Gases
Interaction-assisted topological pumping in few- and many-atom Rydberg arrays
Chenxi Huang, Tao Chen, Qian Liang et al. (+7 more)
Topology can imbue
lattice systems with special properties, notably the presence of robust eigenstates living at their boundary. Through dimensional reduction, the robust bulk band
topology of, e.g., the integer
quantum Hall system can be mapped onto similarly robust charge-pumping dynamics of a topological pump living in one lower dimension. Recent studies have uncovered a rich influence of interactions on the dynamics of topological pumps in nonlinear systems, including the robust pumping of self-bound
solitons. These striking observations in classical nonlinear photonics have raised a number of questions, chiefly if and how this phenomenology persists in strongly correlated
quantum systems and in the few-body limit. Here, using few- and many-atom arrays, we explore how dipolar interactions impact the dynamics of topological population pumping along a Rydberg synthetic dimension. In the few-body limit, we find that dipolar interactions lead to self-bound states that are efficiently pumped along the synthetic dimension, described by an emergent pair-state topological pump. We find that this interaction-assisted pumping persists in many-atom arrays, with a sharpened dependence on the dipolar interaction strength that stems from the enhanced spatial connectivity. These Rydberg-based studies on interaction-assisted topological pumping help connect observations from classical nonlinear photonics to the few-body
quantum limit and pave the way for studies of new strongly correlated
quantum pumping phenomena.
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All authors Chenxi Huang, Tao Chen, Qian Liang, Matthew A. Krebs, Ethan Springhorn, Ruiyu Li, Mingsheng Tian, Kaden R. A. Hazzard, Jacob P. Covey, Bryce Gadway
Mesoscale and Nanoscale Physics
Theory of local orbital magnetization: local Berry curvature
Sariah Al Saati, Karyn Le Hur and Frédéric Piéchon
We develop a thermodynamic theory of local orbital magnetization based on a perturbative expansion of the
magnetic-field-dependent local density of states. Applicable to periodic
crystals, finite systems with open boundaries, and ribbons alike, the formalism resolves orbital
magnetic textures at the sublattice scale. It further reveals a previously unidentified local Berry
curvature that captures the
magnetic-field-induced redistribution of electronic weight in real space. We establish the consistency of the theory across geometries, identify orbital ferro-, antiferro-, and ferrimagnetic phases in both topological and trivial
insulators, and demonstrate that the local Berry
curvature provides a bulk description of
topology in finite systems.
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Materials Science
Shape descriptors of equilibrium states in a quantum lattice model with local multi-well potentials: A geometric analysis near the phase transitions in Sn$_2$P$_2$S$_6$ ferroelectric crystals
S. Özüm, T. Akkurt, R. Erdem et al. (+1 more)
We analyze the
equilibrium states of
quantum lattice model with local multi-well potentials for Sn$_2$P$_2$S$_6$ ferroelectric
crystals using the mean and Gaussian
curvatures ($H$, $K$), curvedness ($C$) and shape index ($S$). From the energy gap, pressure and temperature variations of $H$, $K$, $C$ and $S$, we have reported the
geometric construction of the free energy surfaces for the ferroelectric and paraelectric phases. Their behaviors are explicitly observed near the ferroelectric-paraelectric phase transitions. It is found that $H$, $C$ and $S$ display a cusp singularity at the criticality while $K$ converges to zero on both sides of the critical and tricritical points.
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All authors S. Özüm, T. Akkurt, R. Erdem, N. Güçlü
Materials Science
Active learning potentials for first-principles phase diagrams using replica-exchange nested sampling
Nico Unglert, Michael Ketter and Georg K. H. Madsen
Accurate prediction of materials phase diagrams from first principles remains a central challenge in computational materials science. Machine-learning interatomic potentials can provide near-DFT accuracy at a fraction of the cost, but their reliability crucially depends on the availability of representative training data that span all relevant regions of the potential-energy surface. Here, we present a fully automated active-learning (AL) strategy based on replica-exchange nested sampling (RENS) for the generation of training data and the computation of complete pressure-temperature phase diagrams. In our framework, RENS acts as both the exploration engine and the acquisition mechanism: its intrinsic diversity and likelihood-constrained sampling ensure that the configurations selected for DFT labeling are both informative and thermodynamically representative. We apply the approach to silicon, germanium, and titanium using potentials trained at the r2SCAN level of theory. For all systems, the AL process converges within 10-15 iterations, yielding transferable potentials that reproduce known phase transitions and thermodynamic trends. These results demonstrate that RENS-based AL provides a general and autonomous route to constructing machine-learning interatomic potentials and predicting first-principles phase diagrams across broad thermodynamic conditions.
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Superconductivity
Magnetic field-bias current interplay in HgTe-based three-terminal Josephson junctions
J. Thieme, W. Himmler, F. Dominguez et al. (+8 more)
We investigate HgTe/Nb-based three-terminal Josephson junctions in T-shaped and X-shaped geometries and their critical current contours (CCCs). By decomposing the CCCs into the contributions from individual junctions, we uncover how bias current and
magnetic field jointly determine the collective Josephson behavior. A perpendicular
magnetic field induces a tunable crossover between SQUID-like and Fraunhofer-like interference patterns, controlled by the applied bias. Moreover,
magnetic flux produces pronounced deformations of the CCC, enabling
symmetry control in the $(I_1,I_2)$ plane. Remarkably, we identify a regime of strongly enhanced Josephson diode efficiency, reaching values up to $\eta\approx 0.8$ at low bias and
magnetic field. The experimental results are quantitatively reproduced by resistively shunted junction (RSJ) simulations, which capture the coupled dynamics of current and flux in these multi-terminal superconducting systems.
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All authors J. Thieme, W. Himmler, F. Dominguez, G. Platero, N. Hüttner, S. Hartl, E. Richter, D. A. Kozlov, N. N. Mikhailov, S. A. Dvoretsky, D. Weiss
Mesoscale and Nanoscale Physics · Cross-listed from math.FA
Proof of Kitaev determinant trivialization conjecture
Guo Chuan Thiang
Using ideas from algebraic $K$-theory, we prove that a simple and naturally applicable criterion of Kitaev suffices to trivialize the Fredholm determinant of a multiplicative commutator.
Mesoscale and Nanoscale Physics
Scalable Quantum Photonic Platform Based on Site-Controlled Quantum Dots Coupled to Circular Bragg Grating Resonators
Kartik Gaur, Avijit Barua, Sarthak Tripathi et al. (+12 more)
The scalable integration of solid-state
quantum emitters into photonic nanostructures remains a central challenge for
quantum photonic technologies. Here, we demonstrate a robust and streamlined integration strategy that tackles the long-standing issue of deterministic fabrication on randomly positioned self-assembled
quantum dots (QDs), leveraging a buried-stressor-based site-controlled InGaAs QD platform. We show that this deterministic growth approach enables precise spatial
alignment with circular Bragg grating (CBG) resonators for enhanced emission, eliminating the need for complex and time-consuming deterministic lithography techniques. We fabricated a $6\times6$ SCQD-CBG array with 100% device yield, with 35 devices falling within the radial-offset range where the simulated
photon-extraction efficiency (PEE) exceeds 20%, underscoring the spatial precision and scalability of our fabrication concept. A systematically selected subset of five devices with varying radial displacements reveals clear offset-dependent trends in extraction efficiency, spectral linewidth, and
photon indistinguishability, thereby establishing quantitative bounds on spatial
alignment tolerances. In the best-aligned QD-CBG device, we achieve a PEE of $(47.1\pm3.8)\%$, a linewidth of $(1.41\pm0.22)$ GHz, a radiative decay lifetime of $(0.80\pm0.02)$~ns, a single-
photon purity of $(99.58\pm0.18)\%$, and a Hong-Ou-Mandel two-
photon interference visibility of $(81\pm5)\%$ under quasi-resonant excitation at saturation power. We confirm our conceptual understanding of the effect of emitter-position dependent charge-noise fluctuations in terms of a
quantum-optical model for the (
quantum-)emission properties.
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All authors Kartik Gaur, Avijit Barua, Sarthak Tripathi, Léo J. Roche, Steffen Wilksen, Alexander Steinhoff, Sam Baraz, Neha Nitin, Chirag C. Palekar, Aris Koulas-Simos, Imad Limame, Priyabrata Mudi, Sven Rodt, Christopher Gies, Stephan Reitzenstein
Materials Science
Diamond crystal with Y-defects: spectroscopy and transmission electron microscopy
A.A. Shiryaev, E.A. Vasilev, A.L. Vasilev et al. (+3 more)
The paper presents results of investigation of a natural Ib-IaA diamond containing Y-defects from Yubileinaya kimberlite pipe, Yakutia. Analysis of spatial distribution of nitrogen-related A and C centers and intensity of Infra-red absorption at Raman frequency (1332 cm-1) reveals anticorrelation between these defects. Transmission electron microscopy of a zone with abundant Y-defects shows presence of dislocations in various configurations and numerous clusters of point defects generated by non-conservative dislocation motion. Extended defects with shape resembling thin (1-3 nm) rhombic plates with the largest dimension up to 20 nm are observed. Analysis of contrast of these defects shows that they represent nanosized voids (vacancy clusters). It is suggested that the defects were formed by annihilation of dislocation dipoles with subsequent growth by consumption of vacancies produced by non-conservative motion of dislocations. Upon excitation by 787 nm
laser, numerous narrow photoluminescecne lines are observed between 800-900 nm; their intensity and position show pronounced spatial heterogeneity on scale of few microns. Qualitatively similar behaviour of photoluminescence was earlier noted for hydrogenated nanodiamonds. It is suggested that unusual behaviour of the luminescence lines may be explained by recombination processes at internal walls of the discovered nanovoids.
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All authors A.A. Shiryaev, E.A. Vasilev, A.L. Vasilev, V.V. Artemov, N.V. Gubanov, D.A. Zedgenizov
Quantum Gases · Cross-listed from physics.atom-ph
Coulomb crystallization of xenon highly charged ions in a laser-cooled Ca+ matrix
Leonid Prokhorov, Aaron A. Smith, Mingyao Xu et al. (+17 more)
We report on the sympathetic cooling and Coulomb crystallization of xenon highly charged ions (HCIs) with
laser-cooled Ca$^+$ ions. The HCIs are produced in a compact electron beam ion trap, then charge selected, decelerated, and finally injected into a cryogenic linear Paul trap. There, they are captured into $^{40}$Ca$^+$ Coulomb
crystals, and co-crystallized within them, causing dark voids in their fluorescence images. Fine control over the number of trapped ions and HCIs allows us to realize mixed-species
crystals with arbitrary ordering patterns. By investigating Xe$^{q+}$–Ca$^+$ strings, we confirm the HCI charge states, measure their lifetime and characterize the mixed-species motional modes. Our system effectively combines the established
quantum control toolbox for Ca$^+$ with the rich set of atomic properties of Xe highly charged ions, providing a resourceful platform for optical frequency metrology, searches for signatures of new physics, and
quantum information science.
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All authors Leonid Prokhorov, Aaron A. Smith, Mingyao Xu, Kostas Georgiou, Vera Guarrera, Lakshmi P. Kozhiparambil Sajith, Elwin A. Dijck, Christian Warnecke, Malte Wehrheim, Alexander Wilzewski, Laura Blackburn, Matthias Keller, Vincent Boyer, Thomas Pfeifer, Ullrich Schwanke, Cigdem Issever, Steven Worm, Piet O. Schmidt, José R. Crespo Lopez-Urrutia, Giovanni Barontini
Strongly Correlated Electrons
Experimental benchmark of the quantum-classical crossover in a spin ladder
Hironori Yamaguchi, Itsuki Shimamura, Akira Matsuo et al. (+4 more)
We report a
spin-(1/2, 5/2) three-leg ladder realized in a radical-Mn
polymer, exhibiting an
antiferromagnetic transition and magnetization curves accurately described by classical mean-field theory. Although the underlying
spin model intrinsically supports strong
quantum fluctuations, as confirmed by
quantum Monte Carlo simulations, the real system shows an anomalously complete suppression of
quantum behavior. These findings provide a key experimental
benchmark for the
quantum-classical crossover and suggest that
lattice topology can play a crucial role in tuning the balance between
quantum and classical physics in strongly correlated systems.
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All authors Hironori Yamaguchi, Itsuki Shimamura, Akira Matsuo, Koichi Kindo, Koji Araki, Yoshiki Iwasaki, Masayuki Hagiwara