Materials Science
Single photon emitters in hBN: Limitations of atomic resolution imaging and potential sources of error
David Lamprecht, Shrirang Chokappa, Alissa M. Freilinger et al. (+9 more)
There is a growing interest in identifying the origin of single-
photon emission in hexagonal boron nitride (hBN), with proposed candidates including boron and nitrogen vacancies as well as carbon substitutional dopants. Because
photon emission intensity often increases with sample thickness, hBN flakes used in these studies commonly exceed 30 atomic layers. To identify potential emitters at the atomic scale, annular dark-field scanning transmission electron microscopy (ADF-STEM) is frequently employed. However, due to the intrinsic AA' stacking of hBN with vertically alternating boron and nitrogen atoms, this approach is complicated even in few-layer systems. Here, we demonstrate using STEM image simulations and experiments that, even under idealized conditions, the intensity differences between boron- and nitrogen-dominated columns and carbon substitutions become indistinguishable at thicknesses beyond 17 atomic layers (ca. 6 nm). While vacancy-type defects can remain detectable at somewhat larger thicknesses, also their detection becomes unreliable at thicknesses typically used in photonic studies. We further show that common residual aberrations, particularly threefold astigmatism, can lead to artificial contrast differences between columns, which may result in misidentification of atomic defects. We systematically study the effects of non-radially symmetric aberrations on multilayer hBN and demonstrate that even small residual threefold astigmatism can significantly distort the STEM contrast, leading to misleading interpretations.
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All authors David Lamprecht, Shrirang Chokappa, Alissa M. Freilinger, Barbara Maria Mayer, Maximilian Melchior, Jana Dzíbelová, Darwin Lorber, Luiz H. G. Tizei, Mathieu Kociak, Clemens Mangler, Lado Filipovic, Jani Kotakoski
Mesoscale and Nanoscale Physics
Gate-tunable single terahertz meta-atom ultrastrong light-matter coupling
Elsa Jöchl, Anna-Lydia Vieli, Lucy Hale et al. (+6 more)
We study the electrical tunability of ultrastrong light-matter interactions between a single terahertz
circuit-based complementary split ring resonator (cSRR) and a two-dimensional electron gas. For this purpose, transmission spectroscopy measurements are performed under the influence of a strong
magnetic field at different set points for the electric gate bias. The resulting Landau polariton dispersion depends on the applied electric bias, as the gating technique confines the electrons in-plane down to extremely sub-wavelength dimensions as small as d = 410 nm. This confinement allows for the excitation of standing
plasma waves at zero
magnetic field and an effective tunability of the electron number coupled to the THz resonator. This allows the normalized coupling strength to be tuned in-situ from $\eta$ = 0.46 down to $\eta$ = 0.18. This is the first demonstration of terahertz far-field spectroscopy of an electrically tunable interaction between a single terahertz resonator and electrons in a GaAs
quantum well
heterostructure.
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All authors Elsa Jöchl, Anna-Lydia Vieli, Lucy Hale, Felix Helmrich, Deniz Turan, Mona Jarrahi, Mattias Beck, Jérôme Faist, Giacomo Scalari
Quantum Gases · Cross-listed from math-ph
Momentum Distribution of a Fermi Gas with Coulomb Interaction in the Random Phase Approximation
Niels Benedikter, Sascha Lill and Diwakar Naidu
We analyse the momentum distribution of a three-dimensional
Fermi gas in the mean-field scaling regime in a trial state that was recently proven to reproduce the Gell-Mann-Brueckner correlation energy for Coulomb potentials. For a class of potentials including the Coulomb potential we show that the momentum distribution is given by a step profile corrected by a random phase approximation contribution. Moreover, for potentials with summable
Fourier transform we provide optimal error bounds for the deviation from the random phase approximation. This refines a recent analysis by two of the authors to the physically most relevant potentials and to momenta closer to the
Fermi surface. The proof relies on a double bootstrap method, improved over the earlier analysis to estimate the momentum distribution both globally over all momenta and pointwise. We argue that a similar result can be expected to hold also for the ground state.
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Statistical Mechanics
Burgers dynamics for Poisson point process initial conditions
Patrick Valageas
We investigate the statistical properties of one-dimensional Burgers dynamics evolving from
stochastic initial conditions defined by a Poisson point process for the velocity potential, with a power-law intensity. Thanks to the geometrical interpretation of the solution in the inviscid limit, in terms of first-contact parabolas, we obtain explicit results for the multiplicity functions of shocks and voids, and for velocity and density one- and two-point correlation functions and power spectra. These initial conditions gives rise to self-similar dynamics with probability distributions that display power-law tails. In the limit where the exponent $\alpha$ of the Poisson process that defines the initial conditions goes to infinity, the power-law tails steepen to Gaussian falloffs and we recover the spatial distributions obtained in the classical study by Kida (1979) of Gaussian initial conditions with vanishing large-scale power.
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Mesoscale and Nanoscale Physics
Elimination of the acoustoelectric domain and increasing of the emission intensity by means of shunting the lateral current in the InGaAs/GaAs heterostructures
P.A. Belevskii, M.N. Vinoslavskii and O.S. Pylypchuk
There has been experimentally implemented a technique of neutralization of an acoustoelectric domain under the conditions of the lateral transport of charge carriers in strong electric fields in the multilayer InGaAs/GaAs
heterostructures with
quantum wells. The technique is implemented by means of deposition of a shunting semi opaque silver film on the
heterostructure surface between the ohmic contacts. In absence of shunting the domain appearance leads to current decrease, current oscillations and also to a strong decrease of the band-to-band emission during a voltage pulse applied to the sample. The shunting eliminated the current decrease and enabled it to strongly enlarge the band-to-band emission intensity.
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Soft Condensed Matter · Cross-listed from physics.bio-ph
Exchange controls coarsening of surface condensates
Riccardo Rossetto, Marcel Ernst and David Zwicker
Biological membranes often exhibit heterogeneous
protein patterns, which
cells control. Strong patterns, like the polarity spot in budding yeast, can be described as surface condensates, formed by physical interactions between constituents. However, it is unclear how these interactions affect the material exchange with the bulk. To study this, we analyze a thermodynamically consistent model, which reveals that passive exchange generally accelerates the coarsening of surface condensates. Active exchange can further accelerate coarsening, although it can also fully arrest it and induce complex patterns involving various length scales. We reveal how these behaviors are related to non-local transport via
diffusion through the bulk, rationalizing the various scaling laws we observe and allowing us to interpret biologically relevant scenarios.
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Materials Science
pH-Responsive Glyphosate Adsorption on Hydroxylated Carbon Nanotubes: From Electronic Structure to Molecular Dynamics
H.T. Silva, L.C.S. Faria, T.A. Aversi-Ferreira et al. (+1 more)
This computational study investigates glyphosate adsorption mechanisms on hydroxyl-functionalized carbon nanotubes (CNTs) as an alternative approach for environmental remediation. Single-walled CNTs with (10,0) zigzag chirality were functionalized with hydroxyl groups at concentrations of 5-25% and evaluated for interactions with glyphosate in five different ionization states (G1-G5) corresponding to pH-dependent protonation. Using semi-empirical tight-binding methods implemented in xTB software, molecular geometry optimization, electronic property calculations, topological analyses via
Quantum Theory of Atoms in Molecules (QTAIM), and molecular dynamics simulations at 300K were performed. Results demonstrate that functionalization significantly enhances adsorption capacity, with binding energies becoming increasingly negative at higher OH concentrations and with more deprotonated glyphosate forms (G4 and G5). Electronic coupling analyses reveal optimized charge reactivity and transport in systems with 20-25% OH functionalization. Topological characterization identified 477 bond critical points, confirming donor-acceptor interactions with strong covalent contributions, particularly in highly functionalized systems. Radial distribution function profiles from molecular dynamics simulations demonstrate that functionalization promotes spatial organization on nanotube surfaces, increasing contact regions and reducing molecular mobility. Systems with moderate interactions (CNT+OHx+G1 and CNT+OHx+G3) present environmentally and economically viable solutions, enabling adsorbent regeneration and reuse. The findings indicate that OH-functionalized carbon nanotubes show significant promise for glyphosate detection and capture applications in environmental monitoring and remediation, regardless of the pesticide's ionization state.
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All authors H.T. Silva, L.C.S. Faria, T.A. Aversi-Ferreira, I. Camps
Quantum Gases · Cross-listed from quant-ph
Directional quantum walks of two bosons on the Hatano-Nelson lattice
Sk Anisur, Kartik Singh and Sayan Choudhury
We theoretically investigate the interplay of interactions and non-Hermiticity in the dynamics of two
bosons on the one-dimensional Hatano-Nelson
lattice with non-reciprocal tunneling. We find that the non-reciprocity in the tunneling leads to the formation of an asymmetric density cone during the time-
evolution of the system; the degree of asymmetry can be tuned by tuning the non-reciprocity parameter, $\delta$. Next, we analyze the dynamics of this system in the presence of a static external force and demonstrate that non-Hermiticity leads to asymmetric two-particle Bloch oscillations. Interestingly, when $F=0$ ($F \ne 0$), strong interactions leads to the formation of an inner density-cone (density-hourglass) structure; this inner structure also becomes asymmetric in the presence of non-Hermiticity. We further analyze the spatial correlations and establish that the system exhibits non-reciprocal bunching (anti-bunching) in the presence of weak (strong) interactions. Finally, we examine the growth of the
Quantum Fisher Information, $F_Q$, with time, and demonstrate that $F_Q \propto t^{\alpha}$ where $\alpha \sim 3$. This feature persists for both one- and two-particle walks, thereby demonstrating that this system can be employed as a
quantum-enhanced sensor for detecting weak forces.
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Materials Science
Real Chern insulators in two-dimensional altermagnetic Fe$_2$S$_2$O and Fe$_2$Se$_2$O
Yong-Kun Wang, Shifeng Qian, An-Dong Fan et al. (+1 more)
Altermagnets, recently identified as a third class of collinear
magnetic materials, have attracted significant
attention in condensed matter physics. Despite this growing interest, the realization of real Chern
insulators in intrinsic altermagnetic systems has rarely been reported. In this work, based on first-principles calculations and theoretical analysis, we identify monolayer Fe$_2$S$_2$O and Fe$_2$Se$_2$O as a novel class of two-dimensional altermagnetic real Chern
insulators. We demonstrate that these materials possess altermagnetic ground states and host a nontrivial mirror real Chern number, leading to the emergence of
symmetry-protected zero-dimensional corner states. Notably, these corner modes are
spin-polarized, giving rise to a unique
spin-corner coupling effect. We further show that the real Chern insulating phases and their associated corner states remain robust against
spin-orbit coupling, as well as under both uniaxial and biaxial strain. Additionally, these materials exhibit pronounced linear dichroism and strong optical absorption. Our findings uncover the novel topological character of Fe$_2$S$_2$O and Fe$_2$Se$_2$O, establishing them as promising platforms for exploring real Chern
insulators in altermagnetic systems.
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All authors Yong-Kun Wang, Shifeng Qian, An-Dong Fan, Si Li
Mesoscale and Nanoscale Physics
Negative Refraction of Terahertz Phonons via Interfacial Momentum Compensation
Hao Chen, Zhong-Ke Ding, Yuan Yao et al. (+5 more)
Negative refraction provides a route to steer and focus wave energy flow, but it remains difficult to realize for coherent terahertz (THz)
phonons. The difficulty stems from conventional dispersion-based mechanisms, which require strongly anisotropic or negative-
curvature dispersions, while the long-wavelength acoustic
phonons most favorable for coherent transport are nearly isotropic. Here we overcome this limitation by introducing a momentum compensation mechanism mediated by discrete translational
symmetry. Discrete translational
symmetry parallel to the interface supplies a compensating tangential momentum, reopening transmitted channels beyond the conventional critical condition and enabling negative refraction when this compensation reverses the tangential component. Mode-resolved calculations for hBN/
graphene heterostructures establish this mechanism in laterally stitched in-plane interfaces and show how twisted van der Waals moire superlattices shift the negative-refraction window to lower frequencies. These results identify periodic crystalline interfaces as
symmetry-engineered elements for THz
phonon momentum conversion and wavefront control.
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All authors Hao Chen, Zhong-Ke Ding, Yuan Yao, Chang-Hao Ding, Nannan Luo, Jiang Zeng, Li-Ming Tang, Ke-Qiu Chen
Strongly Correlated Electrons
Emergence of Ferromagnetism from Planar Defects in EuSn2As2 Antiferromagnet
A. Yu. Levakhova, A. L. Vasiliev, N. S. Pavlov et al. (+6 more)
We report an observation and study of monolayer thick structural defects in the
antiferromagnetic (AFM) layered semimetal EuSn2As2. The high resolution transmission electron microscopy revealed the presence of planar defects in the
lattice of the studied single
crystals. Using a combination of microstructural and DFT analysis we demonstrated that a single planar defect forms a monolayer of a distinct phase EuSnAs2, that is different from the EuSn2As2 phase of the bulk
lattice. The smaller distance between Eu layers in the planar defect as well as odd number of Eu atoms in the formula of the defect (EuSnAs2) and of the defect supercell (Eu7Sn12As14) promote formation of local
ferromagnetic (FM) ordering of the Eu atoms. This suggests that on average, the planar defects form a ferrimagnetic minority phase in the
antiferromagnetic (AFM) host
lattice. The obtained results may explain several puzzling features in
magnetic properties of various A-type AFM materials, such as the nonlinear magnetization and
ferromagnetic-type hysteresis in low in-plane fields, the upturn of the
magnetic susceptibility in the AFM state at temperatures approaching zero, and the emergence of the
ferromagnetic-type resonance line in the electron
spin resonance spectrum of the AFM state. The present finding provides new insight into understanding the mechanism of ferromagnetism in quasi-two-dimensional AFM materials: it offers a new way to create an AFM-FM interface by self-docking two different crystalline phases of a chemically pure compound. Thus, this result will facilitate the design and implementation of natural AFM-FM interfaces.
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All authors A. Yu. Levakhova, A. L. Vasiliev, N. S. Pavlov, A. V. Ovcharov, V. I. Bondarenko, A. V. Sadakov, K. S. Pervakov, V. A. Vlasenko, V. M. Pudalov
Other Condensed Matter
When can phonon modes be trapped by arbitrarily weak local defects? Rigorous sufficient conditions in a monatomic lattice
Jaden Thomas, Rodrigo Arrieta, Shu-Ching Yang et al. (+2 more)
Although many studies have shown that localized defects in vibrational
lattices can trap localized
phonon modes for particular geometries, there has been no general proof of localization for arbitrary localized defects of arbitrarily weak strength. This is distinct from the problem of Anderson localization, where random perturbations are spread across the entire
lattice and one aims to prove whether all states become localized. Here, we study the former problem for monatomic 1d and 2d
crystals with nearest-neighbor harmonic interactions, corresponding in 2d to square
lattices of masses and springs, and prove that arbitrary localized perturbations (such as any finite set of defect masses) that decrease the net mass by any amount must lead to localized states. In contrast, the analogous statement is generally false in 3d. Our proof employs a straightforward variational method, inspired by analogous results for the Schrödinger and Maxwell equations, that should be extensible to other discrete systems.
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All authors Jaden Thomas, Rodrigo Arrieta, Shu-Ching Yang, Arthur J. Parzygnat, Steven G. Johnson
Strongly Correlated Electrons · Cross-listed from physics.chem-ph
Encoding electronic ground-state information with variational even-tempered basis sets
Weishi Wang, Casey Dowdle and James D. Whitfield
We propose a system-oriented basis-set design based on even-tempered basis functions to variationally encode electronic ground-state information into molecular orbitals. First, we introduce a reduced formalism of concentric even-tempered orbitals that achieves hydrogen energy accuracy on par with the conventional formalism, with lower optimization cost and improved scalability. Second, we propose a
symmetry-adapted, even-tempered formalism specifically designed for molecular systems. It requires only primitive S-subshell Gaussian-type orbitals and uses two parameters to characterize all exponent coefficients. In the case of the diatomic hydrogen molecule, the basis set generated by this formalism produces a dissociation curve more consistent with cc-pV5Z than cc-pVTZ at the size of aug-cc-pVDZ. Finally, we test our even-tempered formalism against several types of tetra-atomic hydrogen molecules for ground-state computation and point out its current limitations and potential improvements.
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Quantum Gases
Realization of repulsive polarons in the strongly correlated regime
René Henke, Jesper Levinsen, Meera M. Parish et al. (+4 more)
Mobile
impurities interacting with a
quantum medium form quasiparticles known as polarons, a central concept in many-body physics. While the
quantum impurity problem has been extensively studied with ultracold atomic gases, repulsive polarons in the strongly correlated regime have remained elusive. Typically, the
impurity atoms bind into molecules or rapidly decay into deeper lying states before they can acquire an appreciable dressing cloud. Here, we report on the realization of polarons in a strongly repulsive quasi-two-dimensional
quantum gas. Using a superfluid of $^6$Li dimers, we introduce
impurities by promoting a small fraction of the dimers into higher levels of the transverse confining potential. These novel synthetic-
spin polarons give access to the strongly repulsive regime where common decay channels are suppressed. We extract key polaron properties - the energy, quasiparticle residue, and effective mass - using trap modulation and Bragg spectroscopy. Our measurements are well captured by a microscopic T-
matrix approach and
quantum Monte Carlo simulations, revealing deviations from mean-field predictions. In particular, we measure a significant enhancement of the polaron mass, with values exceeding twice the free dimer mass. Our demonstration of a stable repulsive Bose polaron establishes a platform for studying
impurity physics in low-dimensional and strongly correlated systems.
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All authors René Henke, Jesper Levinsen, Meera M. Parish, Jordi Boronat, Grigori E. Astrakharchik, Henning Moritz, Cesar R. Cabrera
Disordered Systems and Neural Networks · Cross-listed from physics.optics
Mie-tronics supermodes and symmetry breaking in nonlocal metasurfaces
Thanh Xuan Hoang, Ayan Nussupbekov, Jie Ji et al. (+3 more)
It is usually believed that
symmetry breaking in photonic systems leads to weaker optical confinement, such as in the case of metasurfaces when bound states in the continuum are replaced by quasi-bound states with lower quality factors (Q factors). Here we show that
symmetry breaking can instead enhance light trapping by strengthening in-plane nonlocal coupling pathways. We consider finite-size arrays of optical resonators supporting Mie resonances (a Mie-tronics platform) and employ diffraction and multiple-scattering analyses. We demonstrate that diffractive bands and Mie-tronics supermodes originate from the same underlying Mie resonances but differ fundamentally in their physical nature. Finite arrays exhibit Q-factor enhancement driven by redistributed radiation channels, and reversing the trends predicted by infinite-
lattice theories. We reveal that controlled
symmetry breaking opens new electromagnetic coupling channels, enabling polarization conversion in nonlocal metasurfaces. These novel findings establish a unified wave-physics platform linking both scattering and diffraction theories. Also, they outline the design principles for multi-functional metasurfaces that exploit nonlocality for advanced light manipulation, computation, and emission control.
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All authors Thanh Xuan Hoang, Ayan Nussupbekov, Jie Ji, Daniel Leykam, Jaime Gomez Rivas, Yuri Kivshar
Strongly Correlated Electrons
Quantum effects in the magnon spectrum of 2D altermagnets via continuous similarity transformations
Raymond Wiedmann, Dag-Björn Hering, Vanessa Sulaiman et al. (+3 more)
We investigate
quantum effects on
magnon excitations in a minimal
spin-1/2 Heisenberg model for 2D altermagnets on the square
lattice. A continuous similarity transformation is applied in momentum space to derive an effective
Hamiltonian that conserves the number of
magnon excitations. This allows us to quantitatively calculate the one-
magnon dispersion, the effects of
magnon-
magnon interactions, and the dynamic structure factor in a certain range of parameters. In particular, we focus on the altermagnetic
spin splitting of the
magnon bands and the size of the roton minimum. We further map out divergencies of the continuous similarity transformation for different types of generators, which signal either the breakdown of the Néel-ordered phase or the presence of significant
magnon decay.
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All authors Raymond Wiedmann, Dag-Björn Hering, Vanessa Sulaiman, Matthias R. Walther, Kai P. Schmidt, Götz S. Uhrig
Other Condensed Matter
Inertial Repulsion from Quantum Geometry
Maike Fahrensohn and R. Matthias Geilhufe
We derive a repulsive, charge-dipole-like interaction for a Dirac particle in a rotating frame, arising from a
geometric $U(1)$ gauge
symmetry associated with the Berry phase. The Lagrangian of this system includes a non-inertial correction due to centrifugal field coupling. By imposing gauge
symmetry and treating it as a full gauge theory, the Lagrangian is extended to include Berry connection and
curvature terms. Upon integrating out the
geometric gauge field, the effective action is obtained. This leads to the emergence of a repulsive, long-range effective interaction in the Lagrangian. Explicitly, in the non-inertial frame of the observer, the
geometric gauge invariance effectively leads to a repulsive Coulomb-interaction in momentum space. In real space, the inertial repulsion manifests in a $1/\vert r\vert^{2}$ potential, which is symmetric about the origin of rotation and mirrors charge-dipole interaction.
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Mesoscale and Nanoscale Physics
Switching perpendicular magnets for Processing-in-memory with voltage gated Weyl Semimetals
Youjian Chen, Hamed Vakili, Md Golam Morshed et al. (+1 more)
Processing-in-
memory (PIM) reduces data transfer latency by rolling
memory and logic elements into one compute location. As an emergent material candidate for such an architecture, we propose a strained Weyl semimetal based
spin-orbit-torque random-access
memory (SWSM-SOTRAM) device. The
spin-orbit torque (SOT) originates from two mechanisms: (1) the inverse
spin Galvanic effect (iSGE), which generates nonequilibrium in-plane
spin accumulation at interfaces, and (2) a bulk
spin Hall effect (SHE), which produces a transverse
spin current carrying out-of-plane
spin angular momentum. The latter is tunable via an exchange Zeeman field. Both effects are evaluated using the tight-binding model coupled with a nonequilibrium Green's function (TB-NEGF) formalism for
quantum transport. Information write is achieved through SOT switching of an out-of-plane free magnet. A piezo attached to a magnetostrictive selector modulates the strain in the latter, leading to the rotation of the magnetization and hence the exchange Zeeman field exerted on the Weyl semimetal. This strain-controlled exchange field enables the
symmetry tuning of the Weyl semimetal and modulation of its
spin Hall effect. The TB-NEGF calculations of SHE and iSGE, combined with Landau-Lifshitz-Gilbert (LLG) simulations of magnetization dynamics, establish the SOT switching mechanism and demonstrate a pathway toward the SWSM-SOTRAM PIM device.
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All authors Youjian Chen, Hamed Vakili, Md Golam Morshed, Avik W. Ghosh
Materials Science
Topological transition and emergent elasticity of dislocation in skyrmion lattice: Beyond Kittel's magnetic-polar analogy
Kohta Kasai, Akihiro Uematsu, Tatsuki Kawakane et al. (+5 more)
Magnetic and polar skyrmions exhibit topologically protected quasiparticle behavior, including emergent fields, deformation, and the formation of a densely packed skyrmion
lattice, beyond conventional domain configurations described by Kittel's law. Analogous to atomic
crystals,
lattice defects, especially dislocations and their associated strain fields, are crucial for understanding the
lattice behavior of skyrmions; however, their features and roles remain insufficiently understood. Here, we show that
magnetic skyrmion dislocations develop a core-split structure due to a significant skyrmion elongation up to 180% of their original length, reaching a topological transition from a single skyrmion to two half-skyrmions. Despite such a distinct structure, the long-range strain fields around the dislocation perfectly obey conventional Volterra's elasticity theory, in contrast to polar skyrmion
lattices, where skyrmion deformations cause a breakdown of the elasticity theory. Furthermore, an energetic analysis shows that Dzyaloshinskii-Moriya interaction drives the large skyrmion deformation of the dislocation core. Our findings not only clarify the coexistence of topological core-reconstruction and a robust long-range elastic field of dislocations in
magnetic skyrmion
lattices, but also reveal that
magnetic and electric domains, long regarded as dual and analogous, exhibit fundamental differences when extended into the regime of collective topological quasiparticles.
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All authors Kohta Kasai, Akihiro Uematsu, Tatsuki Kawakane, Yu Wang, Tao Xu, Chang Liu, Susumu Minami, Takahiro Shimada
Mesoscale and Nanoscale Physics · Cross-listed from math.AP
Dimensional reduction for anyons in the average-field approximation
Qiyun Yang
We study abelian anyons at the mean-field/almost-bosonic level, whose dynamics are governed by the Chern-Simons-Schrödinger system. We consider the dimensional reduction of this 2D model by introducing an anisotropic trapping potential, and derive an effective 1D model after tracing out the tight confinement direction. The resulting effective dynamics in the loose confinement direction is captured by a quintic defocusing nonlinear Schrödinger equation. We rigorously establish this dimensional reduction process in the sense of ground state energies and time-dependent solutions, under an $H^2$ well-posedness assumption.
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Materials Science
Structural characterization and bonding energy analysis for plasma-activated bonding of SiCN films: A reactive molecular dynamics study
Juheon Kim, Minki Jang, Junhyeok Park et al. (+2 more)
Plasma-activated bonding of SiCN films offers high bonding strength at the hybrid-bonding interface, thereby enhancing mechanical reliability. Although experimental studies have shown that the interfacial bonding properties of SiCN films vary with SiCN composition and
plasma treatment parameters, a clear correlation between these parameters and the resulting bonding properties has not yet been established. This study presents an atomistic investigation of SiCN-SiCN
plasma-activated bonding with controlled SiCN composition and
plasma fluence, which performs O2
plasma surface activation, surface hydroxylation, direct bonding, post-bonding annealing, and debonding using reactive molecular dynamics. The structural characterization of the
plasma-activated SiCN surface, including density of various covalent bonds and surface roughness, exhibits composition- and
plasma fluence-dependent chemical and morphological modification. Bonding energy evaluated from atomic traction-separation responses in cohesive zone volume elements (CZVE) during debonding simulations shows a positive correlation with the interfacial Si-O-Si density. Since the interfacial Si-O-Si density reflects the combined effects of these chemical and morphological modifications, the dependence of bonding energy on composition and
plasma fluence is successfully elucidated by the structural characterization. These results establish an atomic-level material-process-property relationship and offer practical guidance for optimizing SiCN composition and
plasma treatment parameters for SiCN-SiCN
plasma-activated bonding.
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All authors Juheon Kim, Minki Jang, Junhyeok Park, Byungjo Kim, Hayoung Chung
Statistical Mechanics
Integrability of a family of clean SYK models from the critical Ising chain
Kohei Fukai and Hosho Katsura
We establish the integrability of a family of Sachdev-Ye-Kitaev (SYK) models with uniform $p$-body interactions. We derive the R-
matrix and mutually commuting transfer
matrices that generate the
Hamiltonians of these models, and obtain their exact eigenspectra and eigenstates. Remarkably, the R-
matrix is that of the critical transverse-field Ising chain. This work reveals an unexpected connection between the SYK model, central to many-body
quantum chaos, and the critical Ising chain, a cornerstone of statistical mechanics.
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Strongly Correlated Electrons
Unraveling Deconfined Quantum Criticality in Non-Hermitian Easy-Plane $J$-$Q$ Model
Xuan Zou, Shuai Yin, Zi-Xiang Li et al. (+1 more)
Deconfined
quantum critical point (DQCP) characterizes the continuous transition beyond Landau-Ginzburg-Wilson paradigm, occurring between two phases that exhibit distinct
symmetry breaking. The debate over whether genuine DQCP exists in physical SU(2)
spin systems or the transition is weakly first-order has persisted for many years. In this letter, we construct a non-Hermitian easy-plane $J$-$Q$ model and perform sign-problem-free
quantum Monte Carlo (QMC) simulation to explore the impact of non-Hermitian microscopic interactions on the transition that potentially features a DQCP. Our results demonstrate that the intensity of the first-order transitions significantly diminishes with the amplification of non-Hermitian interactions, serving as numerical evidence to support the notion that the transition in $J$-$Q$ model is quasi-critical, possibly in the vicinity of the fixed point governing DQCP in the complex plane, described by a non-
unitary conformal field theory (CFT). The non-Hermitian interaction facilitates the approach towards such a complex fixed point in the parameter regime. Furthermore, our QMC study on the non-Hermitian J-Q model opens a new route to numerically investigating the nature of complex CFT in the microscopic model.
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All authors Xuan Zou, Shuai Yin, Zi-Xiang Li, Hong Yao
Statistical Mechanics · Cross-listed from quant-ph
Universal first-passage time statistics for quantum diffusion
Guido Ladenburger, Finn Schmolke and Eric Lutz
First-passage phenomena play a fundamental role in classical
stochastic processes. We here exactly solve a
quantum first-passage time problem for
quantum diffusion driven by measurement noise, a generalization of classical Brownian motion. Such continuous monitoring may trap the measured
quantum system in a decoherence-free subspace, a fraction of the available state space that is isolated from the surroundings, and thus plays an important role in
quantum information science. We analytically determine the first-passage time distribution, whose form neither depends on the system
Hamiltonian nor on the measurement operator, and is therefore universal. These results provide a general framework to investigate the first-passage statistics of diffusive
quantum trajectories.
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Mesoscale and Nanoscale Physics
Discovery of Slot Plasma Excitations in a AlGaN/GaN Plasmonic Crystal
A.R. Khisameeva, A. Shuvaev, I.M. Moiseenko et al. (+6 more)
We experimentally investigate the terahertz spectrum of
plasma excitations in a plasmonic
crystal based on AlGaN/GaN two-dimensional electron system (2DES). While screened plasmon modes with linear dispersion are readily observed in the plasmonic
crystals, the existence of unscreened modes localized in the slots between the gates has remained unobserved until now. We discover this slot
plasma excitation exhibiting square-root dispersion. It turned out that these slot plasmons follow an unconventional wave-vector quantization rule, $q_u=(N + 1/4) \times \pi/l_u$ for even integers $N$, and require the condition for excitation $q_u h \ll 1$, where $h$ is the gate-to-2DES distance and $l_u$ is the slot width. We develop an analytical model that accurately captures the found dispersion and relaxation, revealing a non-trivial $-\pi/4$ phase shift upon plasmon reflection at the gate edge. Experiments demonstrate that the slot plasmons persist up to room temperature, thereby enabling a broad range of opportunities for the advancement of plasmonic devices.
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All authors A.R. Khisameeva, A. Shuvaev, I.M. Moiseenko, P.A. Gusikhin, A.S. Astrakhantseva, A. Pimenov, D.A. Svintsov, I.V. Kukushkin, V.M. Muravev
Strongly Correlated Electrons
SC$^*$ Superconductivity and Spin Stiffnesses in the SU(2) Gauge Theory of the Two-Dimensional Hubbard Model
Demetrio Vilardi and Pietro M. Bonetti
We consider the SU(2) gauge theory for
spin fluctuations in the two-dimensional Hubbard model, where the electron field is fractionalized in terms of spinons and chargons. In this theory, spinons are described by a non-linear sigma model, while chargons are treated as
fermions at a mean-field level. We investigate the instability to a superconducting state SC*, arising from a fractionalized
Fermi liquid (FL*) where pairing between chargons occurs. Consistent with previous studies, our analysis reveals a coexisting phase characterized by both
magnetic and superconducting order for the chargons. The central contribution of this work is the calculation of the feedback of superconductivity on spatial and temporal
spin stiffnesses, thereby quantifying its impact on
spin fluctuations. Our key finding is that superconductivity significantly suppresses these
spin stiffnesses, enhancing
quantum spin fluctuations. This enhancement suggests that superconductivity can play a crucial role in stabilizing
quantum disorder against long-range
magnetic ordering.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Force-Based Reading and Writing of Individual Single-Atom Magnets
Yuuki Adachi, Kazuki Ueda, Yuuki Yasui et al. (+1 more)
The integration of single-atom bits enables the realization of the highest data-density
memory. Reading and writing information to these bits through mechanical interactions opens the possibility of operating the
magnetic devices with low heat generation and high density recording. To achieve this visionary goal, we demonstrate the use of
magnetic exchange force microscopy to read and write the
spin orientation of individual holmium adatoms on MgO thin films. The
spin orientation of the holmium adatom is stabilized by the strong uniaxial anisotropy of the adsorption site and can be read out by measuring the exchange forces between the
magnetic tip and the atom. The
spin orientation can be written by approaching the tip closer to the holmium adatom.We explain this writing mechanism by the
symmetry reduction of the adsorption site of the Ho adatom. These findings demonstrate the potential for information storage with minimal energy loss and pave the way for a new field of atomic-scale mechano-spintronics.
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All authors Yuuki Adachi, Kazuki Ueda, Yuuki Yasui, Yoshiaki Sugimoto
Materials Science
Statistical imaging of NV centers reveals clustered defect formation in diamond
Jason Shao, Richard Monge, Tom Delord et al. (+1 more)
The sharp optical resonances of NV- centers in diamond at cryogenic temperatures offer powerful new capabilities for material characterization, but extracting the most detailed information typically requires careful calibration of individual sensors, limiting scalability. In this work, we use resonant photoluminescence excitation imaging to optically resolve and monitor hundreds of individual NVs across large fields of view, enabling statistical analysis of their spatial distribution with sub-diffraction resolution. This multiplexed, non-destructive approach allows
quantum sensors to characterize the material platform they inhabit. Focusing on CVD-grown diamond, we uncover significant deviations from random distributions, including an unexpectedly high occurrence of closely spaced clusters comprising two or more NVs. These findings suggest non-Poissonian formation dynamics and point to spatially correlated defect generation mechanisms. Beyond offering insight into diamond growth and NV center formation, our approach enables the scalable identification of naturally occurring NV clusters - configurations that are promising for
entanglement-assisted
quantum information protocols and correlated sensing - and establishes a path toward structural and electronic defect analysis in various material hosts at the single-emitter level.
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All authors Jason Shao, Richard Monge, Tom Delord, Carlos A. Meriles
Superconductivity
On the dynamics of the Meissner and the Becker-London effects
Peter Markoš and Richard Hlubina
It is generally accepted that the most fundamental property of a
superconductor is that it exhibits the Meissner effect. Of similar importance is the Becker-London effect, i.e. generation of
magnetic field inside a rotating
superconductor. Hirsch has recently pointed out that, within the conventional theory of superconductivity, the question about how these effects are generated dynamically has not even been asked yet. Here we fill in this gap in the literature by a detailed study of the
evolution of the electromagnetic field for both of these effects. To this end, we solve the Maxwell equations supplemented by the simplest conventional constitutive equation for a
superconductor, namely the London equation. We demonstrate that, contrary to the expectations of Hirsch, the conventional theory does correctly describe the dynamics of both, the Meissner and the Becker-London effect. We find that the dynamics of the studied processes is quite rich and interesting even at this level of description.
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Materials Science
Development of a magnetic interatomic potential for cubic anti-ferromagnets: the case of NiO
Ievgeniia Korniienko, Pablo Nieves, Jakub Sebesta et al. (+2 more)
Interatomic potentials are essential for molecular dynamics simulations of
magnetic materials, yet incorporating
magnetic features into potentials for complex antiferromagnets remains challenging. Nickel
oxide (NiO), a prototypical cubic antiferromagnet, exemplifies this difficulty. Here we develop a methodology to integrate
magnetic properties into interatomic potentials for cubic antiferromagnets by adding a
magnetic Hamiltonian which includes both the Heisenberg exchange and Néel model. We apply this approach to NiO by constructing two potentials: one based on the Born model of ionic solids and another using a reference-free modified embedded atom method. Both potentials include magnetoelastic interactions and are validated against Density Functional Theory calculations, showing excellent agreement in mechanical and
magnetic properties at zero temperature. These models enable large-scale simulations of magnetoelastic phenomena in antiferromagnets and open avenues for molecular dynamics studies involving coupled electric and
magnetic fields in metal
oxides.
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All authors Ievgeniia Korniienko, Pablo Nieves, Jakub Sebesta, Roberto Iglesias, Dominik Legut