Density Wave Research Articles

Horseshoes and spiral waves: capturing the 3D flow induced by a low-mass planet analytically

ABSTRACT The key difficulty faced by 2D models for planet–disc interaction is in appropriately accounting for the impact of the disc’s vertical structure on the dynamics. 3D effects are often mimicked via softening of the planet’s potential; however, the planet-induced flow and torques often depend strongly on the choice of softening length. We show that for a linear adiabatic flow perturbing a vertically isothermal disc, there is a particular vertical average of the 3D equations of motion that exactly reproduces 2D fluid equations for arbitrary adiabatic index. There is a strong connection here with the Lubow–Pringle 2D mode of the disc. Correspondingly, we find a simple, general prescription for the consistent treatment of planetary potentials embedded within ‘2D’ discs. The flow induced by a low-mass planet involves large-scale excited spiral density waves that transport angular momentum radially away from the planet and ‘horseshoe streamlines’ within the coorbital region. We derive simple linear equations governing the flow that locally capture both effects faithfully simultaneously. We present an accurate coorbital flow solution allowing for inexpensive future study of corotation torques, and predict the vertical structure of the coorbital flow and horseshoe region width for different values of adiabatic index, as well as the vertical dependence of the initial shock location. We find strong agreement with the flow computed in 3D numerical simulations, and with 3D one-sided Lindblad torque estimates, which are a factor of 2–3 lower than values from previous 2D simulations.

Coexisting Néel and charge density wave orders in attractive three-color fermions

Coexisting Néel and charge density wave orders in attractive three-color fermions

Simultaneous Characterization of In-Plane and Cross-Plane Resistivities in Highly Anisotropic 2D Layered Heterostructures.

Understanding and characterizing the intrinsic properties of charge carrier transport across the interfaces in van der Waals heterostructures is critical to their applications in modern electronics, thermoelectrics, and optoelectronics. However, there are very few published cross-plane resistivity measurements of thin samples because these inherently 2-probe measurements must be corrected for contact and lead resistances. Here, we present a method to extract contact resistances and metal lead resistances by fitting the width dependence of the contact end voltages of top and bottom electrodes of different contact widths to a model based on current crowding. These contributions are then subtracted from the total 2-probe cross-plane resistance to obtain the cross-plane resistance of the material itself without needing multiple devices and/or etching steps. This approach was used to measure cross-plane resistivities of a (PbSe)1(VSe2)1 heterostructure containing alternating layers of PbSe and VSe2 with random in-plane rotational disorder. Several samples measured exhibited a 4 order of magnitude difference between cross-plane and in-plane resistivities over the 6-300 K temperature range. We also reported the observation of charge density wave transition in the cross-plane transport of the (PbSe)1(VSe2)1 heterostructure. The device fabrication process is fully liftoff compatible, and the method developed enables the straightforward measurement of the resistivity anisotropy of most thin film materials with nm thicknesses.

Impeding conduction by breaking the charge carrier hopping in charge-ordered perovskite BaBiO3 ([formula omitted]): Experimental and theoretical electronic structural correlations

BaBiO3 (BBO), a charge-ordered perovskite with mixed-valent states of Bi (Bi3+ and Bi5+), is known for its charge density wave (CDW) semiconducting and topological insulating properties. BBO has been extensively investigated for its superconducting, electrical, and photocatalytic properties. The present study aims to understand the alterations in the CDW and electronic properties of BaBi0.53+Bi0.55+O3 by valence-selective substitution of Bi3+ and Bi5+ with La3+ and Nb5+, respectively, in the solid solutions BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5). The samples synthesized via high-temperature solid-state reaction method were characterized by powder X-ray diffraction and various spectroscopic techniques (FT-IR, Laser Raman, EPR, XPS, and UPS). Impedance analysis revealed an upsurge in total impedance with the substitution of Bi3+/Bi5+ by La3+/Nb5+ indicating the blocking of electron/hole hopping by disruption of the charge ordering of redox pair Bi3+ and Bi5+. The valence-selective substitution of Bi3+/Bi5+ in BaBiO3 resulted in an alteration of the electronic structure and changes in the bandwidth of BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5) solid solutions, which were confirmed by both theoretical density of states (DOS) calculations and experimental ultraviolet photoelectron spectroscopic (UPS) studies.

Fluid Mechanics, and Its Quantum Developments and Applications

Based on the known theories of fluid mechanics, we research the new quantum fluid mechanics by operator method. Further, we discuss its various developments combined the extensive quantum theory and other theories. Finally, we search possible applications in some aspects: in biology many systems are fluids; in astronomy binary stars, the density wave theory and evolutionary direction on spiral galaxies, and sunspot are researched; in geosciences earthquake, formation of basin and hydrocarbon layer are proposed; in social sciences the social hydrodynamics and corresponding waves and tides, the social synergetics, corruption, etc., are discussed.

TRACE assessment of density wave instability onset with void reactivity feedback under natural circulation

Density wave oscillation (DWO) is an important safety concern for boiling water reactors (BWR) due to their high void fraction in the core. Power extensions to existing reactors such as the Maximum Extended Load Line Limit Analysis Plus (MELLLA+) lead to increase susceptibility of DWO-type instability following an anticipated transient without scram (ATWS). Experiments performed at the Karlstein Thermal Hydraulic Test Facility (KATHY) have reproduced the reactivity feedback mechanism in BWRs under ATWS conditions. Using a neutronics module simulator, the KATHY facility was able to provide data on the effect of different neutronic parameters on DWO onset. This paper serves to assess the capability of the thermal-hydraulics code TRACE V5P7 for simulating DWO onset and development under natural circulation with neutronic feedback. A model of the KATHY natural circulation facility is created in TRACE and a reactivity feedback mechanism is implemented using a manual control scheme to simulate the parametric effects provided by the tests. This comparison allows for an assessment of the TRACE code as well as a better understanding of the instability mechanisms and behavior under the given conditions.

Zein spray-dried microparticles loaded with chemically modified curcumin for active wound healing

Wound healing is a delicate process comprising various phases, of which inflammation constitutes the most critical one, as some wounds fail to evolve from this state due to pre-existing pathologies or medical conditions, becoming chronic and causing pain and serious consequences for the patients. Given this context, innovative strategies able to support the body in the transition through the inflammatory and the proliferative phases are needed. Here, we propose to deliver to the wound zein microparticles (ZμP) loaded with chemically modified curcumin (mCUR), a novel bioactive molecule with strong antioxidant properties. Derived from the classic curcumin, mCUR chemical structure has been modified with an amino phenyl carbonyl group on C4 to overcome the poor bioavailability in the human body and to reach stronger inhibition of inflammatory markers thanks to a higher in vitro efficacy (lower IC50). ZμP were fabricated via spray drying starting from various zein/mCUR ratios. An exhaustive characterization of the physico-chemical properties of ZμP, either empty or loaded, has been carried out, alongside with bioactivity assessments via human keratinocytes and Escherichia coli cultures. All the formulations presented average diameters of 1 μm, resulted biocompatible, and led to an encapsulation efficiency in the range of 78.1–83.0 %. Finally, antioxidant properties of loaded microparticles were assessed via DCFH-DA assay, where a fluorescence decrease proportional to mCUR concentration was clearly visible (down to 41.7 %). These promising results highlight our formulations’ ability to reduce oxidative stress inside the cells, representing a promising strategy to address the problem of chronic wounds, supporting the body in overcoming the inflammatory stage.

Fermi Surface Nesting with Heavy Quasiparticles in the Locally Noncentrosymmetric Superconductor CeRh2As2

Abstract The locally noncentrosymmetric heavy fermion superconductor CeRh2As2 has attracted considerable interests due to its rich superconducting phases, accompanied by possible quadrupole density wave and pronounced antiferromagnetic excitations. To understand the underlying physics, here we report measurements from high-resolution angle-resolved photoemission. Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure, as well as a quasi-two-dimensional Fermi surface (FS) with strong 4f contributions. The FS shows signs of nesting with an in-plane vector q 1 = (π/a, π/a), which is facilitated by the heavy bands near X ¯ arising from the characteristic conduction-f hybridization. The FS nesting provides a natural explanation for the observed antiferromagnetic spin fluctuations at (π/a, π/a), which might be the driving force for its unconventional superconductivity. Our experimental results can be reasonably explained by density functional theory plus dynamical mean field theory calculations, which can capture the strong correlation effects. Our study not only provides spectroscopic signature of the key factors underlying the field-induced superconducting transition, but also uncovers the critical role of FS nesting and lattice Kondo effect in the underlying magnetic fluctuations.

On the Formation of a Quasi-stationary Non-Traveling cluster in the Attractive Hamiltonian Mean-Field Model

Abstract Long-range interacting systems usually exhibit quasi-stationary states that deviate from thermal equilibrium over extended periods of time. In particular, in the attractive Hamiltonian mean-field (HMF) model, one of these states is characterized by traveling clusters of particles in the phase-space, generated by the resonance with two counter-propagating density waves. Here, we report the existence of a third, non-traveling cluster, and we explain its formation by the existence of a stationary wave in the system which is generated as a product of a linear superposition of the other two counter-propagating waves.

Surface-sensitive electronic structure of kagome superconductor CsV3Sb5

Abstract We systematically study the electronic structure of a kagome superconductor CsV3Sb5 at different temperatures covering both its charge density wave state and normal state with angle-resolved photoemission spectroscopy. We observe that the V-shaped band around Γ ¯ shows three different behaviors, referred to as α/α′, β and γ, mainly at different temperatures. Detailed investigations confirm that these bands are all from the same bulk Sb-p z origin, but they are quite sensitive to the sample surface conditions mainly modulated by temperature. Thus, the intriguing temperature dependent electronic behavior of the band near Γ ¯ is affected by the sample surface condition, rather than intrinsic electronic behavior originating from the phase transition. Our result systematically reveals the confusing electronic structure behavior of the energy bands around Γ ¯ , facilitating further exploration of the novel properties in this material.

The de Haas–van Alphen quantum oscillations in the kagome metal RbTi3Bi5

Abstract The kagome system has attracted great interest in condensed matter physics due to its unique structure that can host various exotic states such as superconductivity (SC), charge density waves (CDWs) and nontrivial topological states. The topological semimetal RbTi3Bi5 consisting of a Ti kagome layer shares a similar crystal structure to the topological correlated materials AV3Sb5 (A = K, Rb, Cs) but without the absence of CDW and SC. Systematic de Haas–van Alphen oscillation measurements are performed on single crystals of RbTi3Bi5 to pursue nontrivial topological physics and exotic states. Combining this with theoretical calculations, the detailed Fermi surface topology and band structure are investigated. A two-dimensional Fermi pocket β is revealed with a light effective mass, consistent with the semimetal predictions. The Landau fan diagram of RbTi3Bi5 reveals a zero Berry phase for the β oscillation in contrast to that of CsTi3Bi5. These results suggest that kagome RbTi3Bi5 is a good candidate for exploring nontrivial topological exotic states and topological correlated physics.

Sliding Dynamics of Current-Driven Skyrmion Crystal and Helix in Chiral Magnets.

The skyrmion crystal (SkX) and helix (HL) phases, present in typical chiral magnets, can each be considered as forms of density waves but with distinct topologies. The SkX exhibits gyrodynamics analogous to electrons under a magnetic field, while the HL state resembles topological trivial spin density waves. However, unlike the charge density waves, the theoretical analysis of the sliding motion of SkX and HL remains unclear, especially regarding the similarities and differences in sliding dynamics between these two spin density waves. In this Letter, we systematically explore the sliding dynamics of SkX and HL in chiral magnets in the limit of large current density. We demonstrate that the sliding dynamics of both SkX and HL can be unified within the same theoretical framework as density waves, despite their distinct microscopic orders. Furthermore, we highlight the significant role of gyrotropic sliding induced by impurity effects in the SkX state, underscoring the impact of nontrivial topology on the sliding motion of density waves. Our theoretical analysis shows that the effect of impurity pinning is much stronger in HL compared with SkX, i.e., χ^{SkX}/χ^{HL}∼α^{2} (χ^{SkX}, χ^{HL}: susceptibility to the impurity potential, α (≪1) is the Gilbert damping). Moreover, the velocity correction is mostly in the transverse direction to the current in SkX. These results are further substantiated by realistic Landau-Lifshitz-Gilbert simulations.

Based on experiment and quantum chemical calculations: a study of the co-pyrolysis mechanism of polyesterimide enameled wires with polyvinyl chloride and the catalytic effect of endogenous metal Cu

Pyrolysis technology is a green and efficient method for recycling enameled wires. However, since waste enameled wires are typically recovered from electronic waste, they often contain small amounts of wires and cables. Therefore, during the pyrolysis process of waste enameled wires, it is inevitable for the paint film and the cable sheath to undergo co-pyrolysis. Polyesterimide enameled wires (EPEsI) and polyvinyl chloride (PVC) were chosen as represent enameled wires and cable sheath materials, respectively. Using thermogravimetric analysis with various pyrolysis kinetic analysis methods, the pyrolysis characteristics and kinetics of EPEsI and Mixture (mixture of EPEsI and PVC) were studied. Through synergy analysis and pyrolysis-gas chromatography/mass spectrometry analysis, the influence of PVC on the pyrolysis of EPEsI was elucidated from aspects such as pyrolysis characteristics and product distribution. Based on density functional theory calculations and wave function analysis, the role of endogenous metal Cu in EPEsI on the pyrolysis processes of PEsI and PVC, as well as the mechanism of HCl from PVC on the pyrolysis of PEsI, were clarified.

Is the use of neuromonitoring necessary in Sprengel's deformity surgery?

This study aimed to emphasize the effectiveness of using intraoperative neuromonitoring (IONM) in preventing possible nerve damage in Sprengel's deformity surgery. Eighteen patients who underwent Woodward surgery accompanied by neuromonitoring due to Sprengel's deformity were included in the study. Demographic information of the patients and their clinical and cosmetic results before and after surgery were recorded. Complications that occurred during and after the surgery were recorded. Of the 18 patients who underwent surgery, 12 were female and 6 were male. The mean age of the patients was 4.4 (2-8). The mean shoulder abduction angle of the patients was 84.4 (65-105) degrees before the surgery and 151.1 (125-175) degrees in the first year after the surgery. The mean Cavendish score of the patients was 3.6 (3-4) before the surgery and 1.1 (1-2) in the first year after the surgery. In one patient, there was a decrease in IONM motor-evoked potency signals during the reduction of the intraoperative scapula. Considering some loss of correction in the deformity, the scapula was detected at the point where there was no loss of signals. No patients developed wound problems or infections. In this study, it was determined that the use of neuromonitoring was effective in preventing brachial plexus damage, even if this complication was minimal in patients operated on due to Sprengel's deformity.

Evidence for time-reversal symmetry-breaking kagome superconductivity.

Superconductivity and magnetism are often antagonistic in quantum matter, although their intertwining has long been considered in frustrated-lattice systems. Here we utilize scanning tunnelling microscopy and muon spin resonance to demonstrate time-reversal symmetry-breaking superconductivity in kagome metal Cs(V, Ta)3Sb5, where the Cooper pairing exhibits magnetism and is modulated by it. In the magnetic channel, we observe spontaneous internal magnetism in a fully gapped superconducting state. Under the perturbation of inverse magnetic fields, we detect a time-reversal asymmetrical interference of Bogoliubov quasi-particles at a circular vector. At this vector, the pairing gap spontaneously modulates, which is distinct from pair density waves occurring at a point vector and consistent with the theoretical proposal of an unusual interference effect under time-reversal symmetry breaking. The correlation between internal magnetism, Bogoliubov quasi-particles and pairing modulation provides a chain of experimental indications for time-reversal symmetry-breaking kagome superconductivity.

Femtosecond trimer quench in the unconventional charge-density-wave material 1T′−TaTe2

Ultrafast optical switching of materials properties promises future technological applications, enabled by fundamental insights about microscopic couplings and nonequilibrium phenomena. Transition-metal dichalcogenides (TMDCs) combine photosensitivity with strong correlations, furthering rich phase diagrams and enhanced tunability. The compound 1T′−TaTe2 exhibits an electronically and structurally unique set of charge density waves (CDWs), featuring an unusual increase in conductivity and amplitude modes of low prominence. Compared to other charge-ordered TMDCs, only very few studies addressed the ultrafast response of this material to optical excitation. In particular, the question whether such unconventional properties translate to unusual quench dynamics remains largely unresolved. Here, we investigate the structural dynamics in 1T′−TaTe2 by means of ultrafast nanobeam electron diffraction at an unprecedented repetition rate of 2MHz. We reveal a strongly directional cooperative atomic motion during the one-dimensional quench of the low-temperature trimer lattice. These dynamics are completed within less than 500fs, substantially faster than reported previously. In striking contrast, the periodic lattice distortion of the room-temperature phase is unusually robust against high-density electronic excitation. In conjunction with the known sensitivity of 1T′−TaTe2 to chemical doping, we thus expect the material to serve as a versatile platform for tunable structural control by optical stimuli. Published by the American Physical Society 2024

The instability marsh phenomenon and marginal stability boundary distortion of density wave oscillation in parallel channels

Density wave oscillation (DWO) in parallel channels is an important problem that has been widely studied. The marginal stability boundary (MSB) is often found to be “L" shaped on the Npch-Nsub plane, but some very different shapes were also reported. In this paper, the instability marsh region which could occur in the traditional instable region but having both instability and stability sections was presented and discussed, which is found to be an explanation of the distortion of MSB. The analysis of the instability marsh region showed that the evolution of instability marsh should be due to the stability change when operation condition changes, which can be estimated with the analysis of the two-phase and single phase pressure drop variation, as well as Ma's stability criterion for different heat flux profiles. Variation of instability marsh with different heat flux profile, inlet and outlet resistance coefficient, mass flow and pressure were obtained and analyzed, and the effects of these parameters on instability marsh variation were found to be well interpreted with stability change. The calculation and analysis of instability marsh showed a clear evolution figure of the distortion of MSB under different conditions, and related research could be helpful in better understanding the flow instability in parallel channels.

Unconventional charge density wave in a kagome lattice antiferromagnet FeGe

FeGe is a kagome material that exhibits both charge density wave (CDW) order and magnetic order. The CDW order is developed deep inside the A-type antiferromagnetic phase in FeGe, providing a unique platform to investigate the interplay between CDW and magnetism. However, the driving mechanism of the CDW phase remains controversial. In this work, we performed high-pressure electrical transport and x-ray diffraction measurements combined with density-functional theory calculations to investigate the evolution of the CDW of FeGe under pressure. In contrast to conventional CDW materials, the CDW transition temperature of FeGe increases with increasing pressure, indicating the unconventional mechanism of CDW in this material. More interestingly, another possible CDW with a 3×3×6 superlattice emerges above 20 GPa, which may be explained by the calculated metastable CDW states under high pressure. These observations exclude the possibility of Van Hove singularities nesting as a CDW driving force. Our results unveil versatile CDW states and broaden the study of intertwined electronic states in the magnetic kagome metal FeGe. Published by the American Physical Society 2024

Investigating the superconducting state of 2H−NbS2 as seen by the vortex lattice

2H−NbS2 is a classic example of an anisotropic multiband superconductor, with significant recent work focusing on the interesting responses seen when high magnetic fields are applied precisely parallel to the hexagonal niobium planes. It is often contrasted with its sister compound 2H−NbSe2 because they have similar onset temperatures for superconductivity, but 2H−NbS2 has no charge density wave whereas in 2H−NbSe2 the charge density wave order couples strongly to the superconductivity. Using small-angle neutron scattering, a bulk-sensitive probe, we have studied the vortex lattice and how it responds to the underlying superconducting anisotropy. This is done by controlling the orientation of the field with respect to the Nb planes. The superconducting anisotropy, Γac=7.07±0.2, is found to be field independent over the range measured (0.15 to 1.25 T), and the magnetic field distribution as a function of the applied magnetic field is found to be in excellent quantitative agreement with anisotropic London theory modified with a core-size cutoff correction, providing the first complete validation of this model. We find values of λab=141.9±1.5 nm for the in-plane London penetration depth, and λc∼1µm for the out-of-plane response. The field-independence indicates that we are primarily sampling the larger of the two gaps generating the superconductivity in this material. Published by the American Physical Society 2024

Dynamical decoding of the competition between charge density waves in a kagome superconductor

The kagome superconductor CsV3Sb5 hosts a variety of charge density wave (CDW) phases, which play a fundamental role in the formation of other exotic electronic instabilities. However, identifying the precise structure of these CDW phases and their intricate relationships remain the subject of intense debate, due to the lack of static probes that can distinguish the CDW phases with identical spatial periodicity. Here, we unveil the out-of-equilibrium competition between two coexisting 2 × 2 × 2 CDWs in CsV3Sb5 harnessing time-resolved X-ray diffraction. By analyzing the light-induced changes in the intensity of CDW superlattice peaks, we demonstrate the presence of both phases, each displaying a significantly different amount of melting upon excitation. The anomalous light-induced sharpening of peak width further shows that the phase that is more resistant to photo-excitation exhibits an increase in domain size at the expense of the other, thereby showcasing a hallmark of phase competition. Our results not only shed light on the interplay between the multiple CDW phases in CsV3Sb5, but also establish a non-equilibrium framework for comprehending complex phase relationships that are challenging to disentangle using static techniques.