Atomistic Origin of Diverse Charge Density Wave States in CsV_{3}Sb_{5}.

Kagome metals AV_{3}Sb_{5} (A=K, Rb, or Cs) exhibit intriguing charge density wave (CDW) instabilities, which interplay with superconductivity and band topology. However, despite firm observations, the atomistic origins of the CDW phases, as well as hidden instabilities, remain elusive. Here, we adopt our newly developed symmetry-adapted cluster expansion method to construct a first-principles-based effective Hamiltonian of CsV_{3}Sb_{5}, which not only reproduces the established inverse star of David (ISD) phase, but also predict a series of D_{3h}-n states under mild tensile strains. With such atomistic Hamiltonians, the microscopic origins of different CDW states are revealed as the competition of the second-nearest neighbor V-V pairs versus the first-nearest neighbor V-V and V-Sb couplings. Interestingly, the effective Hamiltonians also reveal the existence of ionic Dzyaloshinskii-Moriya interaction in the high-symmetry phase of CsV_{3}Sb_{5} and drives the formation of noncollinear CDW patterns. Our work thus not only deepens the understanding of the CDW formation in AV_{3}Sb_{5}, but also demonstrates that the effective Hamiltonian is a suitable approach for investigating CDW mechanisms, which can be extended to various CDW systems.

Anisotropic epitaxial stabilization of a low-symmetry ferroelectric with enhanced electromechanical response.

Piezoelectrics interconvert mechanical energy and electric charge and are widely used in actuators and sensors. The best performing materials are ferroelectrics at a morphotropic phase boundary, where several phases coexist. Switching between these phases by electric field produces a large electromechanical response. In ferroelectric BiFeO3, strain can create a morphotropic-phase-boundary-like phase mixture and thus generate large electric-field-dependent strains. However, this enhanced response occurs at localized, randomly positioned regions of the film. Here, we use epitaxial strain and orientation engineering in tandem-anisotropic epitaxy-to craft a low-symmetry phase of BiFeO3 that acts as a structural bridge between the rhombohedral-like and tetragonal-like polymorphs. Interferometric displacement sensor measurements reveal that this phase has an enhanced piezoelectric coefficient of ×2.4 compared with typical rhombohedral-like BiFeO3. Band-excitation frequency response measurements and first-principles calculations provide evidence that this phase undergoes a transition to the tetragonal-like polymorph under electric field, generating an enhanced piezoelectric response throughout the film and associated field-induced reversible strains. These results offer a route to engineer thin-film piezoelectrics with improved functionalities, with broader perspectives for other functional oxides.

Realistic Spin Model for Multiferroic NiI_{2}.

A realistic first-principle-based spin Hamiltonian is constructed for the type-II multiferroic NiI_{2}, using a symmetry-adapted cluster expansion method. Besides single ion anisotropy and isotropic Heisenberg terms, this model further includes the Kitaev interaction and a biquadratic term, and can well reproduce striking features of the experimental helical ground state, that are, e.g., a proper screw state, canting of rotation plane, propagation direction, and period. Using this model to build a phase diagram, it is demonstrated that, (i) the in-plane propagation direction of ⟨11[over ¯]0⟩ is determined by the Kitaev interaction, instead of the long-believed exchange frustrations and (ii) the canting of rotation plane is also dominantly determined by Kitaev interaction, rather than interlayer couplings. Furthermore, additional Monte Carlo simulations reveal three equivalent domains and different topological defects. Since the ferroelectricity is induced by spins in type-II multiferroics, our work also implies that Kitaev interaction is closely related to the multiferroicity of NiI_{2}.

General Theory for Bilayer Stacking Ferroelectricity.

Two-dimensional (2D) ferroelectrics, which are rare in nature, enable high-density nonvolatile memory with low energy consumption. Here, we propose a theory of bilayer stacking ferroelectricity (BSF), in which two stacked layers of the same 2D material, with different rotation and translation, exhibit ferroelectricity. By performing systematic group theory analysis, we find all the possible BSF in all 80 layer groups (LGs) and discover the rules about the creation and annihilation of symmetries in the bilayer. Our general theory can not only explain all the previous findings (including sliding ferroelectricity), but also provide a new perspective. Interestingly, the direction of the electric polarization of the bilayer could be totally different from that of the single layer. In particular, the bilayer could become ferroelectric after properly stacking two centrosymmetric nonpolar monolayers. By means of first-principles simulations, we predict that the ferroelectricity and thus multiferroicity can be introduced to the prototypical 2D ferromagnetic centrosymmetric material CrI_{3} by stacking. Furthermore, we find that the out-of-plane electric polarization in bilayer CrI_{3} is interlocked with the in-plane electric polarization, suggesting that the out-of-plane polarization can be manipulated in a deterministic way through the application of an in-plane electric field. The present BSF theory lays a solid foundation for designing a large number of bilayer ferroelectrics and thus colorful platforms for fundamental studies and applications.

Manipulating two-dimensional magnetic states via electric field and pressure.

Topological spin configurations have been an intriguing topic due to the exotic transport properties and promising applications in spintronic devices. The discovery of two-dimensional (2D) magnetic materials such as CrI3 provides new platforms for manipulating magnetic structures. Here, by first-principles calculations and Monte Carlo methods, we investigated the exchange interaction and magnetic states of 2D van der Waals ferromagnetic/ferroelectric heterostructure CrI3/In2Se3. By switching the polarization in the ferroelectric In2Se3 layer under an electric field and changing the interlayer distance between CrI3 and In2Se3 under pressure, four spin configurations, ferromagnetic states, topological domain wall skyrmions, topological bimerons, and stripe domains can be realized. These striking tunable magnetic states can be understood from the Dzyaloshinskii-Moriya interaction and single-ion anisotropy parameters being modified by switching the polarization and changing the interlayer distance. Our results of controllable topological/non-topological spin states broaden the spin phenomena and potential of spintronic applications in van der Waals heterostructures.

Coexistence and Coupling of Multiple Charge Orderings and Spin States in Hexagonal Ferrite.

The coupling between charge and spin orderings in strongly correlated systems plays a crucial role in fundamental physics and device applications. As a candidate of multiferroic materials, LuFe2O4 with a nominal Fe2.5+ valence state has the potential for strong charge-spin interactions; however, these interactions have not been fully understood until now. Here, combining complementary characterization methods with theoretical calculations, two types of charge orderings with distinct magnetic properties are revealed. The ground states of LuFe2O4 are decided by the parallel/antiparallel coupling of both charge and spin orderings in the adjacent FeO double layers. Whereas the ferroelectric charge ordering remains ferrimagnetic below 230 K, the antiferroelectric ordering undergoes antiferromagnetic-ferrimagnetic-paramagnetic transitions from 2 K to room temperature. This study demonstrates the unique aspects of strong spin-charge coupling within LuFe2O4. Our results shed light on the coexistence and competing nature of orderings in quantum materials.

Magnetization Compensation Temperature and Frustration-Induced Topological Defects in Ferrimagnetic Antiperovskite Mn_{4}N.

First-principles-based simulations are conducted to investigate magnetic properties and topological spin textures in the antiperovskite Mn_{4}N ferrimagnet. A magnetization compensation temperature, resulting from a competition between different Mn sublattices, is found in this system, when under thermal equilibrium. Striking metastable topological states are also discovered, including nanometric hedgehog-antihedgehog pairs that originate from frustrated exchange interactions rather than the usual Dzyaloshinskii-Moriya interaction.

Magnetic-Domain-Wall-Induced Electrical Polarization in Rare-Earth Iron Garnet Systems: A First-Principles Study.

First-principles methods are employed to understand the existence of magnetic-domain-wall-induced electric polarization observed in rare-earth iron garnets. In contrast with previous beliefs, it is found that the occurrence of such polarization neither requires the local magnetic moments of the rare-earth ions nor noncollinear magnetism. It can rather be understood as originating from a magnetoelectric effect arising from ferromagnetic interactions between octahedral and tetrahedral Fe ions at the domain walls, and the mechanism behind is found to be a symmetric exchange-striction mechanism.

Electric-Field Switching of Magnetic Topological Charge in Type-I Multiferroics.

Applying electric field to control magnetic properties is a very efficient way for spintronics devices. However, the control of magnetic characteristics by electric fields is not straightforward, due to the time-reversal symmetry of magnetism versus spatial inversion symmetry of electricity. Such fundamental difficulty makes it challenging to modify the topology of magnetic skyrmionic states with electric field. Here, we propose a novel mechanism that realizes the electric-field (E) switching of magnetic topological charge (Q) in a controllable and reversible fashion, through the mediation of electric polarization (P) and Dzyaloshinskii-Moriya interaction (D). Such a mechanism is coined here EPDQ. Its validity is demonstrated in a multiferroic VOI_{2} monolayer, which is predicted to host magnetic bimerons. The change in magnetic anisotropy is found to play a crucial role in realizing the EPDQ process and its microscopic origin is discussed. Our study thus provides a new approach toward the highly desired electric-field control of magnetism.

Possible Kitaev Quantum Spin Liquid State in 2D Materials with S=3/2.

Quantum spin liquids (QSLs) form an extremely unusual magnetic state in which the spins are highly correlated and fluctuate coherently down to the lowest temperatures, but without symmetry breaking and without the formation of any static long-range-ordered magnetism. Such intriguing phenomena are not only of great fundamental relevance in themselves, but also hold promise for quantum computing and quantum information. Among different types of QSLs, the exactly solvable Kitaev model is attracting much attention, with most proposed candidate materials, e.g., RuCl_{3} and Na_{2}IrO_{3}, having an effective S=1/2 spin value. Here, via extensive first-principles-based simulations, we report the investigation of the Kitaev physics and possible Kitaev QSL state in epitaxially strained Cr-based monolayers, such as CrSiTe_{3}, that rather possess a S=3/2 spin value. Our study thus extends the playground of Kitaev physics and QSLs to 3d transition metal compounds.

Electric-Field Control of Magnetization, Jahn-Teller Distortion, and Orbital Ordering in Ferroelectric Ferromagnets.

Controlling the direction of the magnetization by an electric field in multiferroics that are both ferroelectric and strongly ferromagnetic will open the door to the design of the next generation of spintronics and memory devices. Using first-principles simulations, we report that the discovery that the PbTiO_{3}/LaTiO_{3} (PTO/LTO) superlattice possesses such highly desired control, as evidenced by the electric-field-induced rotation of 90° and even a possible full reversal of its magnetization in some cases. Moreover, such systems also exhibit Jahn-Teller distortions, as well as orbital orderings, that are switchable by the electric field, therefore making PTO/LTO of importance for the tuning of electronic properties too. The origin for such striking electric-field controls of magnetization, Jahn-Teller deformations, and orbital orderings resides in the existence of three different types of energetic coupling: one coupling polarization with antiphase and in-phase oxygen octahedral tiltings, a second one coupling polarization with antiphase oxygen octahedra tilting and Jahn-Teller distortions, and finally a biquadratic coupling between antiphase oxygen octahedral tilting and magnetization.

Early Change in Global Longitudinal Strain is an Independent Predictor of Left Ventricular Adverse Remodelling in Patients With Right Ventricular Apical Pacing.

BACKGROUND: Right ventricular apical (RVA) pacing is related to adverse left ventricular (LV) remodelling. This study assessed changes in global longitudinal strain (GLS) after permanent RVA pacing, and investigated whether GLS at one month can predict later LV ejection fraction (LVEF) decline. METHODS: The study enrolled 68 patients with normal LVEF (≥50%) who underwent dual chamber pacemaker implantation for third-degree atrioventricular block. Global strains and LVEF were assessed using three-dimensional (3D) speckle tracking strain echocardiography (STE). RESULTS: At one month, GLS was significantly lower in those patients who developed pacing-induced LV dysfunction (PIVD), which was defined as a reduction in LVEF ≥5 percentage points at 12 months, than those who did not (-14.9±1.8 vs -16.1±1.7, p=0.014), although GLS was similar at baseline. In patients who developed PIVD, only GLS was significantly reduced at one month compared to baseline (-14.9±1.8 vs -16.6±1.2, p=0.022) whereas LVEF was not. Global longitudinal strain at one month was the only independent predictor for PIVD at 12 months on multivariate analysis (OR, 1.623; 95% CI, 0.986-2.210; p=0.009). Receiver operating characteristic (ROC) analysis showed that GLS at one month had a high predictive accuracy for the development of PIVD at 12 months, with an area under curve (AUC) of 0.88, 94% sensitivity, and 70% specificity. CONCLUSIONS: Global longitudinal strain at one month after pacemaker implantation had high predictive accuracy for identifying subsequent development of PIVD. Global longitudinal strain may be an invaluable parameter to predict LV adverse remodelling following permanent RVA pacing.

[Efficacy and Safety Evaluation of Liujin Runzao Concentrated Decoction in Treating Primary Sjögren's Syndrome].

Objective To evaluate the efficacy and safety of Liujin Runzao Concentrated Decoction (LRCD) for the treatment of primary Sjögren's syndrome (pSS). Methods Forty pSS patients with fluid depletion and distribution obstacles syndrome (FDDOS) were randomly assigned to the experimen- tal group and the control group according to 1:1 proportion. All patients received standard therapy: Radix Paeoniae alba total glycosides 600 mg, twice per day. Patients in the experimental group additionally took LRCD, 30 mL each time, twice per day. The therapeutic course for all was 4 weeks, and two courses for all. The improvement of dry mouth and dry eyes were comprehensively evaluated. Each outcome of composite index constitutions (integrals of dry eyes and dry mouth, salivary flow rate, Schirmer test) was respectively reported. Schirmer test and salivary flow rate were determined as well. Score of TCM syndrome, blood sedimentation,'immunoglobulin, and adverse drug reactions were observed. Results The effective rate of comprehensive effect for dry eyes and dry mouth improvement at the end of 8 weeks was 80% in the experimental group and 35% in the control group, with statistical difference (X² =8. 286, P <0. 05). As for the composition of comprehensive effect for dry eyes and dry mouth improvement: The score for dry eyes and dry mouth decreased in the two groups more after treatment than before treatment. The difference in pre-post treatment score for dry eyes and dry mouth at week 8 was higher in the experimental group than in the control group. The difference in pre-post treatment score at week 8 was 1. 71 (95% Cl: -0. 37 -3. 78) between the two groups (P <0. 05). The difference in pre-post treatment Schirmer test and salivary flow rate at week 8 was higher in the experimental group than in the control group, but with on statistical difference (P >0. 05). The difference in pre-post treatment Schirmer test and salivary flow rate at week 8 was 2. 74 mL/15 min (95% Cl: 0. 49 -4.98) and 0. 13 mm/5 min (95% Cl: 0. 92 -1. 23) between the two groups (P <0. 05). The score of TCM syndrome decreased more in the two groups, as compared with before treatment. The difference in pre-post treatment score of TCM syn- drome at week 8 was 1. 71 (95% CI: -1. 40 -4. 81) between the two groups (P >0. 05). One case of uri- nary tract infections occurred in the control group, while no obvious adverse event occurred in the exper- imental group. Conclusion Standard treatment combined LRCD showed better comprehensive effect for dry eyes and dry mouth in pSS patients with FDDOS, and was more safe.

Fractional quantum ferroelectricity.

For an ordinary ferroelectric, the magnitude of the spontaneous electric polarization is at least one order of magnitude smaller than that resulting from the ionic displacement of the lattice vectors, and the direction of the spontaneous electric polarization is determined by the point group of the ferroelectric. Here, we introduce a new class of ferroelectricity termed Fractional Quantum Ferroelectricity. Unlike ordinary ferroelectrics, the polarization of Fractional Quantum Ferroelectricity arises from substantial atomic displacements that are comparable to lattice constants. Applying group theory analysis, we identify 28 potential point groups that can realize Fractional Quantum Ferroelectricity, including both polar and non-polar groups. The direction of polarization in Fractional Quantum Ferroelectricity is found to always contradict with the symmetry of the "polar" phase, which violates Neumann's principle, challenging conventional symmetry-based knowledge. Through the Fractional Quantum Ferroelectricity theory and density functional calculations, we not only explain the puzzling experimentally observed in-plane polarization of monolayer α-In2Se3, but also predict polarization in a cubic compound of AgBr. Our findings unveil a new realm of ferroelectric behavior, expanding the understanding and application of these materials beyond the limits of traditional ferroelectrics.

Memristive switching in the surface of a charge-density-wave topological semimetal.

Owing to the outstanding properties provided by nontrivial band topology, topological phases of matter are considered as a promising platform towards low-dissipation electronics, efficient spin-charge conversion, and topological quantum computation. Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states, which could greatly facilitate topological electronic research. However, ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers. In this study, we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal (TaSe4)2I. We find that the surface state of (TaSe4)2I presents out-of-plane ferroelectric polarization due to surface reconstruction. With the combination of ferroelectric surface and charge-density-wave-gapped bulk states, an electric-switchable barrier height can be achieved in (TaSe4)2I-metal contact. By employing a multi-terminal-grounding design, we manage to construct a prototype ferroelectric memristor based on (TaSe4)2I with on/off ratio up to 103, endurance over 103 cycles, and good retention characteristics. The origin of the ferroelectric surface state is further investigated by first-principles calculations, which reveals an interplay between ferroelectricity and band topology. The emergence of ferroelectricity in (TaSe4)2I not only demonstrates it as a rare but essential case of ferroelectric topological materials, but also opens new routes towards the implementation of topological materials in functional electronic devices.

Spin disorder control of topological spin texture.

Stabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the order-disorder skyrmion lattices transition. In addition, non-trivial topological solitons, such as skyrmioniums and skyrmion bags, are realized at room temperature. Our work highlights the influence of random spin control of non-trivial topological spin textures.

Degradation Mechanism of a Sauce-Glazed Ware of the Song Dynasty Salvaged out of the Water at Dalian Island Wharf: Part I-The Effect of the Surface-Attached Composite Coagula.

Dalian Island is located in the sea area near Pingtan County, Fujian, Southeast China. The sea area used to be the junction of the eastern and western ship routes on the Maritime Silk Road, and is also an important region for underwater archaeology in China. This study focused on a sauce-glazed ware of the Song Dynasty, with serious degradation, which was salvaged out of the water at the Dalian Island Wharf. Optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and micro-Raman spectroscopy were used to comprehensively analyze the composition, phase attributes and microstructure of the ware and the surface-attached coagula. The findings revealed that the sea wave-borne debris scoured the surface of the ware, causing mechanical damage to varying degrees and a significant decrease in its degradation resistance. This was the primary factor accounting for the poor preservation state of the salvaged ceramic ware, and the precondition for the subsequent attachment of marine organisms and the deposition of inorganic pollutants. The calcareous skeletons formed on the surface induced by the bio-mineralization of coralline algae (a type of marine plant) could resist the mechanical action caused by the motion of sea waves, thereby slowing down the ware's degradation process. In other words, the calcareous skeletons played a 'bio-protective' role to a certain degree. In addition, inorganic pollutants represented by iron rusts also participated in the corrosion of the glaze. Some pollutants were directly deposited on the pits and cracks on the surface of the ware, which brought stress to the glaze and glaze/body interface, causing the glaze to further crack and spall. Moreover, iron rusts reacted with the glaze, leading to chemical alteration, accompanied by the formation of iron silicate as the alteration product. Anorthite crystals in the interlayer did not participate in the reaction but remained at the original position. The alteration product gradually replaced the original glass phase of the glaze and entered into the body via pores and cracks. In conclusion, the complex degradation morphology of the salvaged sauce-glazed ware could be attributed to the combined action of mechanical damage, marine bio-fouling, and chemical alteration.

Clinical significance of the expression levels of serum transforming growth factor-ß and CXC type chemokine ligand 13 in primary Sjogren's syndrome patients.

OBJECTIVE: The aim of this study was to investigate the expression levels of the serum transforming growth factor-ß1 (TGF-ß1) CXC type chemokine ligand 13 (CXCL13) in primary Sjogren's syndrome (pSS) patients and its correlation with disease severity. METHOD: Thirty patients with pSS admitted to Nanjing Traditional Chinese Medicine Affiliated Hospital of Nanjing University of Traditional Chinese Medicine from January 2021 to December 2022 were included as the pSS group, while 30 patients who underwent physical examination during the same period were included as the control group. The levels of TGF-ß1 and CXCL13 were detected. The diagnostic value of TGF-ß1 and CXCL13 for pSS was analyzed. Detection of serum TGF-ß1 and CXCL13 levels in pSS patients with different disease activities and lip gland pathological grading of pSS was done. We compared the correlation between TGF-ß1 and CXCL13 levels and disease activity and labial gland pathological grading in pSS patients. RESULT: The TGF-ß1 and CXCL13 levels in the pSS group were higher than those in the control group. The area under the receiver operating characteristic (ROC) curve (AUC) for TGF-ß1 and CXCL13 diagnosis of pSS was 0.790 (95% confidence interval (CI): 0.720~0.861) and 0.838 (95% CI: 0.778~0.898), respectively. The serum TGF-ß1 and CXCL13 levels of pSS patients significantly increase with the increase of disease activity and lip gland pathological grading. The TGF-ß1 and CXCL13 levels in pSS patients were positively correlated with disease activity and lip gland pathological grading. CONCLUSION: The levels of TGF-ß1 and CXCL13 in pSS patients were increased, and it was closely related to disease activity and lip gland pathological grading, which can be used as an effective indicator for the diagnosis of pSS. Key Points • The TGF-ß1 and CXCL13 levels in the pSS group were higher than those in the control group. • The TGF-ß1 and CXCL13 levels in pSS patients were positively correlated with disease activity and lip gland pathological grading. • TGF-ß1 and CXCL13 can be used as an effective indicator for the diagnosis of pSS.

Assembling Diverse Skyrmionic Phases in Fe3 GeTe2 Monolayers.

Skyrmionic magnetic states are promising in advanced spintronics. This topic is experiencing recent progress in 2D magnets, with, for example, a near 300 K Curie temperature observed in Fe3 GeTe2 . However, despite previous studies reporting skyrmions in Fe3 GeTe2 , such a system remains elusive, since it has been reported to host either Néel-type or Bloch-type textures, while a net Dzyaloshinskii-Moriya interaction (DMI) cannot occur in this compound for symmetry reasons. It is thus desirable to develop an accurate model to deeply understand Fe3 GeTe2 . Here, a newly developed method adopting spin invariants is applied to build a first-principle-based Hamiltonian, which predicts colorful topological defects assembled from the unit of Bloch lines, and reveals the critical role of specific forms of fourth-order interactions in Fe3 GeTe2 . Rather than the DMI, it is the multiple fourth-order interactions, with symmetry and spin-orbit couplings considered, that stabilize both Néel-type and Bloch-type skyrmions, as well as antiskyrmions, without any preference for clockwise versus counterclockwise spin rotation. This study also demonstrates that spin invariants can be used as a general approach to study complex magnetic interactions.