Materials Science
Confinement in metal-organic frameworks as a route to harnessing liquid barocalorics in the solid-state
Ming Zeng, Frederic Rendell-Bhatti, Eamonn T. Connolly et al. (+5 more)
Barocaloric (BC) effects at
liquid-vapor transitions in hydrofluorocarbons drive most commercial technologies used for heating and cooling in the heating, ventilation and air-conditioning sector. However, these fluids suffer from huge global warming potential and alternative gases are less efficient, toxic or flammable. Solid-solid and solid-
liquid BC materials have zero global warming potential and could even improve on current device efficiencies. Whilst solid-
liquid BCs typically outperform solid-solid BCs, the latter are advantageous as they avoid leaks and present easier handling and recyclability thus facilitating waste management. Here we confine the solid-
liquid BC stearic acid inside the nanopores of a functionalised metal-organic framework (MOF) and demonstrate that the colossal BC properties are retained in a solid-state material. Moreover, the enhanced interactions between the pore surface and the BC material allow a level of active control over the thermal response, as opposed to passive encapsulation. Our results open novel avenues to exploit and tune colossal BC effects in a wide range of combinations of solid-
liquid BC materials embedded within functionalized MOFs, without the associated engineering drawbacks.
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All authors Ming Zeng, Frederic Rendell-Bhatti, Eamonn T. Connolly, Yang Wang, Josep-Lluís Tamarit, Ross S. Forgan, Pol Lloveras, David Boldrin
Materials Science
Towards the First Realization of Weyl Magnons in the Non-Coplanar Antiferromagnet MnTe$_2$
Ahmed E. Fahmy, Archibald J. Williams, Yufei Li et al. (+9 more)
Using a combination of band representation analysis, inelastic
neutron scattering (INS), magneto-Raman spectroscopy measurements, and linear
spin wave theory, we establish that the non-coplanar antiferromagnet MnTe$_2$ is a tunable Weyl
magnon material, hosting
symmetry-protected topological nodal lines in its
magnon band structure, protected by the the non-coplanar nature of the
antiferromagnetic ordering, that transition into Weyl
magnons upon the application of
symmetry-breaking perturbations using an external
magnetic field. By constructing a
spin model that reproduces the observed INS
magnon spectra and field-dependence of the Raman $\Gamma$-
magnons, we directly probe the topological
magnon nodal lines and observe their associated signature of non-trivial
topology through the pseudo-
spin winding of the scattering intensity in angular scans near the nodal lines. Finally, we discuss the emergence of Weyl
magnons in the spectrum through an external
magnetic field, and analyze the associated
magnon thermal
Hall effect allowed by the cubic-
symmetry breaking and the associated
magnon surface modes, shedding light on future in-field INS and thermal
Hall experiments. This work establishes a clear magnonic analog to Weyl electrons, enabling further exploration of topological behavior in bosonic systems and highlighting the interplay between
magnetic order and band
topology in non-coplanar antiferromagnets.
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All authors Ahmed E. Fahmy, Archibald J. Williams, Yufei Li, Thuc T. Mai, Kevin F. Garrity, Matthew B. Stone, Mohammed J. Karaki, Sara Haravifard, Angela R. Hight Walker, Rolando Valdés Aguilar, Joshua E. Goldberger, Yuan-Ming Lu
Strongly Correlated Electrons
Global approximations to correlation functions of strongly interacting quantum field theories
Yuanran Zhu, Yang Yu, Efekan Kökcü et al. (+2 more)
We introduce a method for constructing global approximations to correlation functions of strongly interacting
quantum field theories, starting from perturbative results. The key idea is to employ interpolation method, such as the two-point Padé expansion, to interpolate the weak and strong coupling expansions of correlation function. We
benchmark this many-body interpolation approach on two prototypical models: the
lattice $\phi^4$ field theory and the 2D Hubbard model. For the $\phi^4$ theory, the resulting two point Padé approximants exhibit uniform and global convergence to the exact correlation function. For the Hubbard model, we show that even at second order, the Padé appproximant already provides reasonable characterization of the Matsubara Green's function for a wide range of parameters. Finally, we offer a heuristic explanation for these convergence properties based on analytic function theory.
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All authors Yuanran Zhu, Yang Yu, Efekan Kökcü, Emanuel Gull, Chao Yang
Quantum Gases
Quasi-two-dimensional soliton in a self-repulsive spin-orbit-coupled dipolar binary condensate
S. K. Adhikari
We study the formation of
solitons in a uniform quasi-two-dimensional (quasi-2D)
spin-orbit (SO) coupled self-repulsive binary dipolar and nondipolar Bose-Einstein condensate (BEC) using the mean-field Gross-Pitaevskii equation. For a weak SO coupling, in a nondipolar BEC, one can have three types of degenerate
solitons: a multi-ring
soliton with intrinsic vorticity of angular momentum projection $+1$ or $-1$ in one component and 0 in the other, a circularly-asymmetric
soliton and a stripe
soliton with stripes in the density. For an intermediate SO couplings, the multi-ring
soliton ceases to exist and there appears a square-
lattice soliton with a spatially-periodic pattern in density on a square
lattice, in addition to the degenerate circularly-asymmetric and stripe
solitons. In the presence of a dipolar interaction, with the polarization direction aligned in the quasi-2D plane, only the degenerate circularly-asymmetric and stripe
solitons appear.
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Materials Science · Cross-listed from physics.app-ph
Enhanced diffusion in self-nanoconfined water channels between periodically modulated surfaces: insights from molecular dynamics simulations
Bruno H. S. Mendonça, Elizane E. de Moraes and Hélio Chacham
Water nanoconfinement is known to occur inside material void spaces, such as 2D confinement between surfaces, 1D confinement inside nanotubes, and variable-dimension confinement inside nanoporous materials. In the present work we investigate, through molecular dynamics simulations, the morphologies and self-
diffusion coefficient of water channels that are nanoconfined in the void space between adjacent surfaces of nanotube bundles - an existing class of materials. In our simulations, we begin with water filling completely the void space, and then we progressively increase the inter-surface separation, maintaining the water content. We find that, as the inter-surface separation progresses, the dimensionality of the water channel decreases from 2D to 1D, the latter consisting of self-confined water channels along surface grooves. The morphologies and self-
diffusion coefficients of these 1D water nanochannels are strongly dependent on the nature of the water-surface interaction and on the diameter of the nanotubes. Interestingly, as we decrease the nanotube diameter from 10 to 5 nm, the self-
diffusion coefficients of the 1D channels increase by tenfold for hydrophilic surfaces and by sixfold for hydrophobic surfaces, surpassing, in both cases, the bulk water values. We also investigated the water channels at the interstitial voids of the bulk bundle material, finding 1D water channels that are similar to the surface ones.
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Strongly Correlated Electrons
Comment on: "The future of the correlated electron problem", arXiv:2010.00584
V.R. Shaginyan and A.Z. Msezane
In our comment we show that some of the very difficult problems have been successfully solved. We have to focus on the resolved problems, since the authors claims: Our hope, however, is that the topics we have presented will provide inspiration for others working in this field and motivation for the idea that significant progress can be made on very hard problems if we focus our collective energies. Thus, there is no need to mislead potential researchers.
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Materials Science
Thermodynamic parameters of the eta' phase in an AlZnMgCu alloy synthesized by mechanical alloying
Maria del V. Valera M and Ney J. Luiggi A
We synthezised an AlZnMgCu
alloy through mechanical alloying and, using Xray diffraction (XRD), identified the formation of the eta
prime phase after 40 hours of grinding. Using reaction-free isoconversion theory, we determined that this phase exhibits two different behaviours depending on the heating rate (beta): the eta
prime phase at low beta and the eta phase at high beta.The activation energy values at low beta are consistent with the
diffusion energies of copper, zinc and magnesium in aluminium. Significant qualitative and quantitative differences in the thermodynamic barriers (Delta H, Delta G and Delta S) are observed for beta values above or below 20 deg C min minus 1.
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Soft Condensed Matter
Relevance of Aggregate Anisotropy in Sheared Suspensions of Carbon Black
Victor Tänzel, Fabian Coupette, Marisol Ripoll et al. (+1 more)
Carbon Black is a filler frequently used in conductive suspensions or nanocomposites, in which it forms networks supporting electric conductivity. Although Carbon Black aggregates originate from a presumably isotropic aggregation process, the resulting particles are inherently anisotropic. Therefore, they can be expected to interact with shear flow, which significantly influences material properties. In this study, we investigate sheared suspensions of Carbon Black aggregates to elucidate the impact of aggregate anisotropy on the rheological properties. We aim at concentrations below and above the conductivity percolation threshold and comprehensively characterize particle behavior under flow conditions. Aggregates assembled by a
diffusion-limited aggregation process are simulated with Langevin dynamics in simple shear flow. The simulations reveal a clear
alignment of the aggregates' long axis with the flow direction, an increase in tumbling frequency with higher shear rates, and a shear-thinning response. This behavior closely parallels that of rod-like particles and underlines the significance of the anisotropic nature of Carbon Black aggregates. These findings will facilitate the optimization of nanocomposite precursor processing and the tailoring of Carbon Black-based conductive suspensions.
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All authors Victor Tänzel, Fabian Coupette, Marisol Ripoll, Tanja Schilling
Strongly Correlated Electrons
Evolution of charge-density-wave soft phonon modes in $\mathrm{Pd}_x\mathrm{ErTe}_3$
Avishek Maity, Stephan Rosenkranz, Raymond Osborn et al. (+8 more)
We investigated the
lattice dynamics of quasi-two-dimensional Pd-intercalated $\mathrm{ErTe}_3$ in relation to its charge-density-wave (CDW) transitions by means of x-ray diffuse and meV-resolution inelastic x-ray scattering. In pristine $\mathrm{ErTe}_3$, CDW order develops at orthogonal in-plane wave vectors $\boldsymbol{\mathrm{q}}_{1}^{c} = (0, 0, 0.29)$ (the $c\text{-}\mathrm{CDW}$) and $\boldsymbol{\mathrm{q}}_{2}^{a} = (0.31, 0, 0)$ (the $a\text{-}\mathrm{CDW}$), with transition temperatures $T_{1}^{c} = 270$ K and $T_{2}^{a} = 160$ K, respectively. Remarkably, we observe diffuse x-ray scattering already near the higher transition temperature $T_{1}^{c}$ along $a\text{-}\mathrm{CDW}$ but at a slightly different wave vector $\boldsymbol{\mathrm{q}}_{1}^{a} = (0.29, 0, 0)$. Inelastic x-ray scattering for $\mathrm{Pd}_{0.01}\mathrm{ErTe}_3$ shows that a partial
phonon softening at $\boldsymbol{\mathrm{q}}_{1}^{a}$, underscoring the strong competition between ordering tendencies along the nearly equivalent in-plane axes of the orthorhombic
lattice. For intercalation levels $x \geq 0.02$, the $a\text{-}\mathrm{CDW}$ state is suppressed. Nevertheless, a similar correlation between
phonon softening and diffuse scattering persists along the $[100]$ direction, again observed at $\boldsymbol{\mathrm{q}}_{1}^{a} = (0.29, 0, 0)$ and $T_{1}^{c}$. These findings suggest that the $a\text{-}\mathrm{CDW}$ is fully suppressed for $x \geq 0.02$, and that the residual diffuse scattering at $\boldsymbol{\mathrm{q}}_{1}^{a}$ originates from the partial
phonon softening associated with the $c\text{-}\mathrm{CDW}$, reflected by the near equality of the absolute size of $\boldsymbol{\mathrm{q}}_{1}^{c}$ and $\boldsymbol{\mathrm{q}}_{1}^{a}$.
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All authors Avishek Maity, Stephan Rosenkranz, Raymond Osborn, Rolf Heid, Ayman H. Said, Ahmet Alatas, Joshua A. W. Straquadine, Matthew J. Krogstad, Anisha G. Singh, Ian R. Fisher, Frank Weber
Materials Science · Cross-listed from physics.optics
Microscale selective laser sintering of Cu nanoparticles with a short-wavelength nanosecond laser
Youwen Liang, Bo Shen and Wan Shou
Microscale additive manufacturing of reflective copper is becoming increasingly important for microelectronics and microcomputers, due to its excellent electrical and thermal conductivity. Yet, it remains challenging for state-of-the-art commercial metal 3D printers to achieve sub-100-micron manufacturing. Two aspects are sub-optimal using commercial
laser powder bed fusion systems with infrared (IR)
lasers (wavelength of 1060-1070 nm): (1) IR
laser has a low absorption rate for Cu, which is energy-inefficient for manufacturing; (2) short wavelength
lasers can potentially offer higher resolution processing due to the diffraction-limited processing. On the other hand,
laser sintering or melting typically uses continuous wave (CW)
lasers, which may reduce the manufacturing resolution due to a large heat-affected zone. Based on these facts, this study investigates the UV (wavelength of 355 nm) nanosecond (ns)
laser sintering of Cu nanoparticles. Different
laser processing parameters, as well as different nanoparticle packing densities, are studied. Our results show that a short-wavelength
laser can reduce the required energy for sintering with decent morphology, and a densified nanoparticle powder bed favors continuous melting. We further show that sub-20 micron printing can be readily achieved with a UV ns
laser. These findings provide new insights into short-wavelength
laser-metal nanoparticle interactions, which may pave the way to achieve high-resolution micro and nano-scale additive manufacturing.
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Strongly Correlated Electrons
Topological edge states in two-dimensional $\mathbb{Z}_4$ Potts paramagnet protected by the $\mathbb{Z}_4^{\times 3}$ symmetry
Hrant Topchyan, Tigran Hakobyan, Mkhitar Mirumyan et al. (+2 more)
We construct a two-dimensional bosonic
symmetry-protected topological (SPT) paramagnet protected by an on-site $G=\mathbb{Z}_4^{\times 3}$
symmetry, starting from a three-component $\mathbb{Z}_4$ Potts paramagnet on a triangular
lattice. Within the group-
cohomology framework, $H^{3}(G,U(1))\cong \mathbb{Z}_4^{\times 7}$, we focus on a "colorless" cocycle representative obtained by antisymmetrizing the basic $\mathbb{Z}_4$ three-cocycle, and generate the corresponding SPT
Hamiltonian via a cocycle-induced nonlocal
unitary transformation followed by
symmetry averaging. For open geometry, we derive the boundary theory explicitly: one color sector decouples, while the nontrivial edge reduces to an interacting $\mathbb{Z}_4$ chain with next-to-nearest-neighbor constraints that admits a compact dressed-Potts form. Using DMRG we show that the boundary model is gapless, with the lowest gap scaling as $1/L$ and an
entanglement-
entropy scaling consistent with a conformal field theory of central charge $c=2.191(4)\simeq 11/5$. The rational value $c=11/5$ matches the coset $SU(3)_3/SU(2)_3$, making it a candidate for the continuum description of the $\mathbb{Z}_4^{\times 3}$ edge; we outline spectral and
symmetry-resolved diagnostics needed to test this identification at the level of conformal towers beyond the central charge.
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All authors Hrant Topchyan, Tigran Hakobyan, Mkhitar Mirumyan, Tigran A. Sedrakyan, Ara Sedrakyan
Mesoscale and Nanoscale Physics
Beyond spin-1/2: Multipolar spin-orbit coupling in noncentrosymmetric crystals with time-reversal symmetry
Masoud Bahari, Kristian Mæland, Carsten Timm et al. (+1 more)
We develop a
symmetry-adapted multipolar $\mathbf{k}\cdot\mathbf{p}$ theory close to the bulk $\Gamma$ point for time-reversal-symmetric, noncentrosymmetric $C_{3v}$
crystals in the strong atomic
spin-orbit-coupling ($jj$-coupling) limit. Using a $j\in\{1/2,3/2,5/2\}$ multiplet basis appropriate for heavy-element p- and d-bands, we systematically construct all
symmetry-allowed
spin-orbit coupling terms up to fifth order in momentum and generalize the usual
spin texture to a total-angular-momentum texture. For $j>1/2$, multipolar
spin-orbit coupling qualitatively reshapes
Fermi surfaces and makes the
topology of Bloch states band dependent. This leads to anisotropic high-$j$ textures that go beyond a single Rashba helix. We classify these textures by their total-angular-momentum vorticity $W_{n}$ for every energy band and identify distinct $|W_{n}|=1,2,5$ phases. We show that their crossovers generate enhanced and nonmonotonic current-induced
spin-polarization responses, namely the Edelstein effect, upon tuning the chemical potential. Our results provide a
symmetry-based framework for analyzing and predicting multipolar
spin-orbit coupling, total-angular-momentum textures, and spintronic responses in heavy-element materials without an inversion center.
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All authors Masoud Bahari, Kristian Mæland, Carsten Timm, Björn Trauzettel
Soft Condensed Matter
Anomalous Translational Dynamics of Molecular Probes Near the Polymer Glass Transition
Jaladhar Mahato, Siyang Wang and Laura J. Kaufman
The origin of the dramatic slowdown of dynamics near the glass transition temperature (Tg) remains a long-standing fundamental and unresolved issue in soft condensed matter. While single-molecule (SM) experiments using fluorescent probes have provided critical insight for molecular and polymeric glass formers through rotational measurements, translational dynamics remain largely unexplored in such systems at the molecular length scale. Here, we report SM translational dynamics of molecular probes in high molecular weight polystyrene at three temperatures near Tg. The probes exhibit quasi-stationary position fluctuations, non-Gaussian displacement distributions, sub-diffusive transport with anti-correlated displacements, and a characteristic translational relaxation time. The observations are quantitatively described using a microscopic framework based on the generalized Langevin equation and supported by numerical modeling for heterogeneous transport. The translational dynamics of the probes provides direct microscopic evidence of dynamic heterogeneity and suggests a pathway to more fully understand glassy dynamics in glass formers near Tg.
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Mesoscale and Nanoscale Physics
Simulating alternating bias assisted annealing of amorphous oxide tunnel junctions
Alexander C. Tyner and Alexander V. Balatsky
Amorphous
oxide tunneling barriers, primarily formed from aluminum, represent one of the most widely adopted platforms for superconducting
quantum bits (
qubits). To overcome challenges associated with defects and sample variance among the tunneling barriers, the methodology of alternating bias assisted annealing (ABAA) was introduced in Pappas et. al[1]. The process of applying alternating bias to the barrier and subsequently aging before use was shown to reduce defects in the barrier. Namely, defects that give rise to two-level systems, coupling to the
qubit and expediting decoherence. In this work we replicate an expedited ABAA process through a combination of ab-initio molecular dynamics and machine-learned potentials, illuminating how ABAA effects the energy landscape of the barrier.
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Materials Science
Orbital torque and efficient magnetization switching using ultrathin Co|Al light-metal interfaces: Experiments and modeling
N. Sebe, A. Pezo, S. Krishnia et al. (+5 more)
The emergence of the orbital degree of freedom in modern orbitronics offers a promising alternative to heavy metals for the efficient control of magnetization. In this context, identifying interfaces that exhibit orbital-momentum locking and an orbital Rashba-Edelstein response to an external electric field is of primary importance. In this work, we experimentally investigate the Co/Al system and extend the study to Co/Pt/Al structures. We show that inserting ultrathin Pt layers between Co and Al can significantly modify the orbital properties, highlighting the critical role of Co/Al orbital bonding in generating orbital polarization. We further model the orbital response of these systems using semi-phenomenological approaches and linear-response theory within the framework of density-functional theory.
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All authors N. Sebe, A. Pezo, S. Krishnia, S. Collin, J.-M. George, A. Fert, V. Cros, H. Jaffrès
Strongly Correlated Electrons
Tensor network approach to momentum-resolved spectroscopy in non-periodic super-moiré systems
Anouar Moustaj, Yitao Sun, Tiago V. C. Antão et al. (+1 more)
Computing spectral functions in large, non-periodic super-moiré systems remains an open problem due to the exceptionally large system size that must be considered. Here, we establish a tensor network methodology that allows computing momentum-resolved spectral functions of non-interacting and interacting super-moiré systems at an atomistic level. Our methodology relies on encoding an exponentially large tight-binding problem as an auxiliary
quantum many-body problem, solved with a many-body kernel
polynomial tensor network
algorithm combined with a
quantum Fourier transform tensor network. We demonstrate the method for one and two-dimensional super-moiré systems, including super-moiré with non-uniform strain, interactions treated at the mean-field level, and quasicrystalline super-moiré patterns. Furthermore, we demonstrate that our methodology allows us to compute momentum-resolved spectral functions restricted to selected regions of a super-moiré, enabling direct imaging of position-dependent electronic structure and minigaps in super-moiré systems with non-uniform strain. Our results establish a powerful methodology to compute momentum-resolved spectral functions in exceptionally large super-moiré systems, providing a tool to directly model
quantum twisting microscope experiments in twisted van der Waals
heterostructures.
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All authors Anouar Moustaj, Yitao Sun, Tiago V. C. Antão, Jose L. Lado
Soft Condensed Matter
Elastic properties of polycatenane chains and ribbons
James M. Polson, Liam MacNevin, Alaaddin Elobeid et al. (+1 more)
Single-chain elasticity is of fundamental importance in
polymer physics, as it underlies many of the unique properties of
polymer systems. Recently, there has been interest in characterizing the elastic properties of catenanes, molecular architectures composed of linked molecular rings. To date most studies have focused on the force-extension behavior of polycatenane and catenane dimers. In this study, we employ Monte Carlo computer simulations to investigate the elastic properties of a collection of catenane chains. In addition to polycatenane, we also examine the properties of catenane ribbons constructed by connecting two or three polycatenane chains together with a variable number of side-link rings. After first characterizing the behavior of free polycatenane chains and catenane ribbons, we examine their mechanical response to both an elongational force and a torque applied to the end rings of the chain. We find that the stretching induced by the force is counterbalanced by increasing the torque, which tends to twist the chains and in so doing reduce the extension length. At low torque, the twist angle of the end rings of the chain varies linearly with torque, and the associated torsional spring constant, characterizing the resistance of the chain to twist with the applied torque, tends to increase with stretching force. Relative to polycatenane, ribbons tend to be more elongated at low force and less elongated at strong force. In addition, increasing the ribbon width dramatically increases the torsional stiffness of the chain. Finally, decreasing the degree of side-linking in ribbons tends to decrease slightly the extension length at moderate force and to increase the torsional stiffness for sufficiently large gaps.
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All authors James M. Polson, Liam MacNevin, Alaaddin Elobeid, Carlos E. Padilla Robles
Superconductivity
Lattice-decoupled rotatable stripe-like charge order within the strange metal phase of 2M-WS2
Kebin Xiao, Yunkai Guo, Daran Fu et al. (+11 more)
In
quantum materials, charge orders typically stabilize in specific crystallographic orientations, though their formation mechanisms may vary. Here, using low-temperature scanning tunneling microscopy (STM), we discover a
lattice-decoupled rotatable stripe-like charge order coexisting with superconductivity in 2M-WS2. The charge order manifests five distinct orientations across different sample regions, yet maintains an identical wavelength. This directional decoupling from host
lattice challenges existing paradigms. First-principles calculations of
phonon spectra and nesting function fail to explain the ordering mechanism. Intriguingly, the transition temperature of the charge orders exhibits spatial variations (21-46 K), coinciding with the temperature range of the recently reported strange metal phase in this material. This correlation suggests that the interplay between strong electronic correlations and electron-
phonon coupling must be critically evaluated to elucidate the emergence of this unconventional charge order.
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All authors Kebin Xiao, Yunkai Guo, Daran Fu, Yuqiang Fang, Yating Hu, Jingming Yan, Yucong Peng, Yuyang Wang, Yongkang Ju, Peizhe Tang, Xiangang Wan, Fuqiang Huang, Qi-Kun Xue, Wei Li