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Antiferromagnets (AFMs) possess great potential in spintronics because of their immunity to external magnetic disturbance, the absence of a stray field or the resonance in the terahertz range1,2. The coupling of insulating AFMs to spin–orbit materials3–7 enables spin transport via AFM magnons. In particular, spin transmission over several micrometres occurs in some AFMs with easy-axis anisotropy8,9. Easy-plane AFMs with two orthogonal, linearly polarized magnon eigenmodes own unique advantages for low-energy control of ultrafast magnetic dynamics2. However, it is commonly conceived that these magnon modes are less likely to transmit spins because of their vanishing angular momentum9–11. Here we report experimental evidence that an easy-plane insulating AFM, an α-Fe2O3 thin film, can efficiently transmit spins over micrometre distances. The spin decay length shows an unconventional temperature dependence that cannot be captured considering solely thermal magnon scatterings. We interpret our observations in terms of an interference of two linearly polarized, propagating magnons in analogy to the birefringence effect in optics. Furthermore, our devices can realize a bi-stable spin-current switch with a 100% on/off ratio under zero remnant magnetic field. These findings provide additional tools for non-volatile, low-field control of spin transport in AFM systems. Easy-plane antiferromagnet materials promise low-energy control of ultrafast magnetic dynamics in future spintronics applications, but host magnons with vanishing angular momentum, which makes spin transport via magnons unlikely. Through interference of two linearly polarized propagating magnons, spin transport over micrometre distances is yet possible.

Anammox bacteria are chemolithotrophic organisms growing on the conversion of ammonium and nitrite with bicarbonate as the sole carbon source. Meanwhile, anammox bacteria display a metabolic versatility to sustain their metabolism. However, there is less attention on the Fe0/Fe2+-dependent autotrophic denitrification by anammox consortia. In this study, the autotrophic nitrate reduction using different valence of iron (Fe0, Fe2+ and Fe0+ Fe2+, respectively) as electron donors by anammox consortia were firstly explored in continuous feeding mode. Results revealed anammox consortia showed high adaptability to the niche wherein containing nitrate and iron. They could generate nitrite and ammonium from iron-dependent nitrate reduction, and hence support their central metabolism. During 60-days operation, the maximum nitrate and total nitrogen removal efficiency reached 88.43% and 80.77%, respectively, with coexistence of Fe0 and Fe2+. The expression of key functional genes involved in nitrate reduction (including narG, napA and nrfA) in 16S rRNA level revealed the coupling of dissimilatory nitrate reduction to nitrite, dissimilatory nitrite reduction to ammonia (DNRA), and anammox processes possibly play pivotal role in nitrogen loss under Fe0/Fe2+ condition. Meanwhile, abiotic reduction by Fe0/Fe2+ also contributed nitrate reduction to provide nitrite and ammonium for anammox consortia. Activities of two vital enzymes hydrazine dehydrogenase (HDH) and nitrate oxidoreduetase (NAR) also inferred higher microbial activities with co-existence of Fe0 and Fe2+. The present study confirms and further extends the versatile metabolisms of Anammox consortia, also it can help to circumvent the accumulation of nitrate produced by anammox process itself and increase the quality of discharge.

To achieve the simultaneous removal of NH4+-N and NO3−-N in F−-containing semiconductor wastewater by coupled S0-driven autotrophic denitrification and Anammox process, the effect of variable F− concentration on the Anammox process was investigated by batch experiments. The denitrifying ammonium oxidation (Deamox) reactor was then started-up to explore the feasibility of the coupling of Anammox and sulfur autotrophic denitrification (SADN) for the treatment of semiconductor wastewater. Short-term variation of F− concentration has an obviously effect on the activity of Anammox sludge, but didn't affect the nitrogen conversion rate. The activity of Anammox obviously decreased after long-term operation of the Deamox reactor when influent F− concentrations reached 552 mg/L. The sensitivity of Anammox bacteria to F− concentration is stronger than that of SADN bacteria. Total nitrogen removal efficiency of 98% and total nitrogen removal rate of 4.11 kg/(m3·d) were achieved in the Deamox reactor, when the F− was pre-treated by calcium ions. Moreover, the high-throughput 16S rRNA gene sequence analysis indicated that variation in F− concentrations could influence the structure and functional of microbial communities in the Deamox process. Candidatus Kuenenia, Thiobacillus and Sulfurimonas were main functional bacteria that achieved symbiotic.

N6-methyladenosine (m6A) is the most abundant-internal modification of eukaryotic mRNA. m6A can be installed and removed by specific enzymes. The "writer," "eraser," and "reader" of m6A modification have been reported. These discoveries facilitate our understanding of the functional significance of m6A. m6A plays an essential role in diverse biological processes by recruiting the corresponding YTH domain-containing proteins, as well as recruiting additional translation initiation factors. Here, we provide an update on the various aspects of YTH domain-containing proteins, including an introduction to the YTH domain, the categories, distribution in cells, and biological roles of YTH proteins. Then we focus on the mechanisms that YTH proteins recognize m6A and mediate the fate of methylated-RNAs in eukaryotic cells.

An efficient and stable combined denitrification-partial nitrification-Anammox process with a dual recycling system was used to remove nitrogen from mature landfill leachate. After 155 d of operation, the NO3− as the PN-Anammox byproduct was almost treated with biodegradable organic carbon in raw wastewater in a pre-denitrification reactor by external recycling system. When raw landfill leachate with NH4+-N concentration of 1900 mg/L was treated, an integrated reactor with airlift recycling was combined with the PN and Anammox reactions to efficiently remove NH4+ from the inflow. The total nitrogen concentration of effluent stabilized at 20 mg/L and total nitrogen removal efficiency was 99%. The maximum NO2− production rate in the aerobic zone was 2.2 kg/(m3·d) and the maximum nitrogen removal rate in the anaerobic zone was 21.4 kg/(m3·d). The most common phyla among the nitrification and the Anammox functional bacteria were Nitrosomonas, Candidatus Kuenenia, and Candidatus Brocadia after landfill leachate treatment.

In the tip clearance flow, the dominant vortex is the tip leakage vortex (TLV), which has a significant impact on the hydraulic and cavitation performance of axial flow machineries. In order to reveal the impact mechanism of the gap size on the TLV, gap flows with two gap sizes, i.e., τ=0.2 (2 mm) and τ=1.0 (10 mm), are numerically investigated. A NACA0009 hydrofoil is selected to create the gap flow, with an incoming velocity of 10 m/s and an attack angle of 10 deg. The results show that the two flow cases are significantly different in terms of vortex feature and the leakage flow distribution. In the small gap, a type of jet-pattern flow appears, whereas a type of rolling-pattern flow passes over the large gap. The vertical velocity gradient of the leakage flow has a decisive influence on the TLV trajectory. In addition, for the large gap, the axial velocity in the vortex center exceeds the incoming flow. This jet-like state of axial velocity can be maintained for a long distance, making the vortex more stable. However, the axial velocity in the case of τ=0.2 cannot stay at the jet-like state and rapidly switches to a wake-like state.

The constituent particles of matter can arrange themselves in various ways, giving rise to emergent phenomena that can be surprisingly rich and often cannot be understood by studying only the individual constituents. Discovering and understanding the emergence of such phenomena in quantum materials-especially those in which multiple degrees of freedom or energy scales are delicately balanced-is of fundamental interest to condensed-matter research1,2. Here we report on the surprising observation of emergent ferroelectricity in graphene-based moire heterostructures. Ferroelectric materials show electrically switchable electric dipoles, which are usually formed by spatial separation between the average centres of positive and negative charge within the unit cell. On this basis, it is difficult to imagine graphene-a material composed of only carbon atoms-exhibiting ferroelectricity3. However, in this work we realize switchable ferroelectricity in Bernal-stacked bilayer graphene sandwiched between two hexagonal boron nitride layers. By introducing a moire superlattice potential (via aligning bilayer graphene with the top and/or bottom boron nitride crystals), we observe prominent and robust hysteretic behaviour of the graphene resistance with an externally applied out-of-plane displacement field. Our systematic transport measurements reveal a rich and striking response as a function of displacement field and electron filling, and beyond the framework of conventional ferroelectrics. We further directly probe the ferroelectric polarization through a non-local monolayer graphene sensor. Our results suggest an unconventional, odd-parity electronic ordering in the bilayer graphene/boron nitride moire system. This emergent moire ferroelectricity may enable ultrafast, programmable and atomically thin carbon-based memory devices.

We study the stability of the Wilson-Fisher fixed point of the quantum $\text{O}(2N)$ vector model to quenched disorder in the large-$N$ limit. While a random mass is strongly relevant at the Gaussian fixed point, its effect is screened by the strong interactions of the Wilson-Fisher fixed point. This enables a perturbative renormalization group study of the interplay of disorder and interactions about this fixed point. We show that, in contrast to the spiralling flows obtained in earlier double-$\ensuremath{\epsilon}$ expansions, the theory flows directly to a quantum critical point characterized by finite disorder and interactions. The critical exponents we obtain for this transition are in remarkable agreement with numerical studies of the superfluid-Mott glass transition. We additionally discuss the stability of this fixed point to scalar and vector potential disorder and use proposed boson-fermion dualities to make conjectures regarding the effects of weak disorder on dual Abelian Higgs and Chern-Simons-Dirac fermion theories when $N=1$.

For over two decades, sulfate reduction with ammonium oxidation (SRAO) had been reported from laboratory experiments. SRAO was considered an autotrophic process mediated by anammox bacteria, in which ammonium as electron donor was oxidized by the electron acceptor sulfate. This process had been attributed to observed transformations of nitrogenous and sulfurous compounds in natural environments. Results obtained differed largely for the conversion mole ratios (ammonium/sulfate), and even the intermediate and final products of sulfate reduction. Thus, the hypothesis of biological conversion pathways of ammonium and sulfate in anammox consortia is implausible. In this study, continuous reactor experiments (with working volume of 3.8L) and batch tests were conducted under normal anaerobic (0.2 ≤ DO > 0.5 mg/L) / strict anaerobic (DO > 0.2 mg/L) conditions with different biomass proportions to verify the SRAO phenomena and identify possible pathways behind substrate conversion. Key findings were that SRAO occurred only in cases of high amounts of inoculant biomass under normal anaerobic condition, while absent under strict anaerobic conditions for same anammox consortia. Mass balance and stoichiometry were checked based on experimental results and the thermodynamics proposed by previous studies were critically discussed. Thus anammox bacteria do not possess the ability to oxidize ammonium with sulfate as electron acceptor and the assumed SRAO could, in fact, be a combination of aerobic ammonium oxidation, anammox and heterotrophic sulfate reduction processes.

Natural language processing covers a wide variety of tasks with token-level or sentence-level understandings. In this paper, we provide a simple insight that most tasks can be represented in a single universal extraction format. We introduce a prototype model and provide an open-source and extensible toolkit called OpenUE for various extraction tasks. OpenUE allows developers to train custom models to extract information from the text and supports quick model validation for researchers. Besides, OpenUE provides various functional modules to maintain sufficient modularity and extensibility. Except for the toolkit, we also deploy an online demo with restful APIs to support real-time extraction without training and deploying. Additionally, the online system can extract information in various tasks, including relational triple extraction, slot & intent detection, event extraction, and so on. We release the source code, datasets, and pre-trained models to promote future researches in http://github.com/zjunlp/openue.

The feasibility of using Feammox coupled with nitrate-dependent Fe(II) oxidizing (NAFO) to cause the simultaneous conversion of NH4+ and NO3− was explored by inoculation with Feammox sludge and the use Fe cycling as catalyst. After 61 days operation, the simultaneous conversion of NO3− and NH4+ occurred with the presence of interconversion between Fe(III) and Fe(II). The conversion ratio of NH4+ to NO3− stabilized at 0.9–1. The results of isotopic tracing and microbial diversity analysis indicated that NH4+ was first oxidized to NO2− by Fe(III), then NO3− was reduced to NO2− and N2 by the Fe(II) produced in Feammox process, and finally, the NO2− produced in NAFO process underwent an Anammox process with the remaining NH4+ to yield N2. The results showed the simultaneous continuous conversion process of NO3− and NH4+ with limited Fe as a catalyst was a coupled process of Feammox, Anammox, and NAFO under the anaerobic conditions.

The phosphorus recovery efficiency in PAOs-biofilm system is so far limited to stimulating phosphorus release by adding concentrated organic carbon solution during the anaerobic stage. In present study, a PAOs-biofilm sequence batch reactor (BSBR) were operated to investigate whether increase of the phosphorus storage content via DO control can stimulate the release in the biofilm. During the operation of BSBR for 160 days, the phosphorus content in biofilm (Pbiofilm) was doubled via increasing dissolved oxygen (DO) from 4 to 6 mg/L. With the COD of 200 mg/L in the anaerobic phase, the phosphorus release was enhaced, resulting in an significant increase of phosphorus concentration from 94.85 to 179.5 mg/L in recirculated solution. Batch tests further clarified explicitly the increase of Pbiofilm stimulated a phosphorus release rate but this must be balanced since high Pbiofilm reduced the phosphorus removal capacity of the biofilm. With analysis of P31-NMR, Ortho-P and Poly-P were the main phosphorus species stored in biofilm. The microbial cell played a more important role than EPS in phosphorus storage. The dominant phylum in the master reactor was Proteobacteria with an abundance of 64.4%, in which the Rhodocyclaceae was the dominant PAOs with an abundance of 10.1%. The outcome of this study elucidated that increase of phosphorus storage via DO control which facilitated more efficient phosphorus release with much lower organic carbon source consumption during the enrichment of phosphorus. Meanwhile, we provided a new perspective for the recovery of phosphorus in future wastewater treatment plants.

Artificial moir\'e superlattices in 2d van der Waals heterostructure is a new venue for realizing and controlling correlated electronic phenomena. Recently, twisted bilayer WSe$_2$ emerged as a new robust moir\'e system hosting a correlated insulator at moir\'e half-filling over a range of twist angle. In this work, we present a theory of this insulating state as an excitonic density wave due to intervalley electron-hole pairing. We show that exciton condensation is strongly enhanced by a van Hove singularity near the Fermi level. Our theory explains the remarkable sensitivity of the insulating gap to the vertical electric field. In contrast, the gap is weakly reduced by a perpendicular magnetic field, with quadratic dependence at low field. The different responses to electric and magnetic field can be understood in terms of pair-breaking versus non-pair-breaking effects in a BCS analog of the system. We further predict superfluid spin transport in this electrical insulator, which can be detected by optical spin injection and spatial-temporal imaging., Comment: 10 pages, 8 figures. To appear in Nature Communications

Continuous phase transitions associated with the onset of a spontaneously broken symmetry are thought to be successfully described by the Landau-Ginzburg-Wilson-Fisher theory of fluctuating order parameters. In this work we show that such transitions can admit new universality classes which cannot be understood in terms of a theory of order parameter fluctuations. We explicitly demonstrate continuous time reversal symmetry breaking quantum phase transitions of $3+1$-D bosonic systems described by critical theories expressed in terms of a deconfined gauge theory with massless Dirac fermions instead of the fluctuating Ising order parameter. We dub such phase transitions "Landau transitions beyond Landau description" (LBL). A key feature of our examples is that the stability of the LBL fixed points requires a crucial global symmetry, which is non-anomalous, unbroken, and renders no symmetry protected topological phase throughout the phase diagram. Despite this, there are elementary critical fluctuations of the phase transition that transform projectively under this symmetry group. We also construct examples of other novel quantum critical phenomena, notably a continuous Landau-forbidden deconfined critical point between two Landau-allowed phases in $3+1$-D., 18 pages, 6 figures

The effects of salinity changes on nitrogen transformation efficiency and recoverability were studied by using a partial nitration (PN)- anaerobic ammonium oxidation (Anammox) integrated reactor. The changes of microbial community structure and population abundance during the increase and decrease of salinity were also analyzed by 16S rRNA gene high-throughput sequencing. The results showed that when the salinity was increased to 1.35%, the combined PN-Anammox process achieved the maximum stimulated and total nitrogen removal rate (TNRR) arrived at 1.1kg/(m3·d). When the salinity was higher than 1.35%, the activities of AOB and Anammox bacteria began to be inhibited. When the salinity reached 2.4%, the TNRR decreased to 60%. TNRR was fast restored, when salinity was reduced to 0.11%. The genes of AOB and Anammox bacteria indicated that the TNRR of the reactor was restored after salinity inhibition, but the functional microbial community structure and abundance had relatively large, irreversible changes.

The InGaN/GaN multi-quantum-wells (MQWs) solar cells employing the surficial GaN nanostructure as light traps were investigated. The performance of the InGaN/GaN MQWs solar cell with nano holes surface shows an obvious advantage over that with nano poles, much less than the planar one. From the measurements of EQE and photoluminescence spectra, the enhancement of photoelectric response contributes to the device performances. Because the effective light absorption is increased, the conversion efficiency significantly improves from 1.02% (planar surface) up to 2.235% (nano holes surface). Although the performance is still low, it is exactly an effective method to enhance the conversion efficiency via introducing nanostructures on the surface of the InGaN/GaN MQWs cells.

In this work, a novel nitrate (NO3−) reduction pathway by anaerobic ammonium oxidation (anammox) biomass was firstly discovered with the intracellular carbon sources as the only electron donors. And the possible reaction mechanism was deduced to be intracellular dissimilatory nitrate reduction to ammonium (DNRA) pathway according to the experimental results. In batch experiments, without any external electron donors, NO3−-N (about 50 mg/L) was reduced to N2 within 48 h, and a small amount of NO2−-N was detected (the maximum of 2 mg/L) with the anammox biomass concentration of 4400 mg/L. Acetylene (4.46 mmol/L) addition resulted in obvious NH4+ accumulation during NO3− degradation by anammox biomass, since acetylene mainly interfered in hydrazine (N2H4) generation from NH4+ and NO. Without HCO3− addition, the NO3−-N degradation rate was slower than that with HCO3− addition. Simultaneously, glycogen contents inside anammox biomass decreased to 133.22 ± 1.21 mg/g VSS and 129.79 ± 1.21 mg/g VSS with and without HCO3−, respectively, from 142.20 ± 0.61 mg/g VSS. In the long-term experiment, anammox biomass stably degraded NO3−-N without external electron donors addition, and the maximum removal efficiency of NO3−-N reached 55.4%. The above results indicated the anammox bacteria utilized the DNRA pathway to reduce NO3− to NO2− and further NH4+, then normal anammox metabolism would continue to convert the produced NO2− and NH4+ to N2. The intracellular stored carbon sources (e.g., glycogen) were supposed to be electron donors for NO3− degradation. This capability would enhance the viability and living space of anammox bacteria in different natural ecosystems, and make it plausible that complete nitrogen removal could be implemented only by the anammox process.

An InGaN/GaN solar cell including a dual multiple quantum wells (MQWs) structure is investigated. It shows an obvious advantage over the conventional InGaN/GaN cell, which only contains a single MQWs structure. Because the short current density ( ${J} _{\mathrm { {sc}}})$ increases, the 1 sun power conversion efficiency significantly improves from 0.62% (single MQWs cell) to 1.02% (dual MQWs cell). From the measurement of EQE and PL spectra, the enhancement of effective photoelectric response within the solar spectrum mainly contributes to the high device performance, due to the introduced upper MQWs of higher In content.

Author(s): Kozii, V; Bi, Z; Ruhman, J | Abstract: The experimental observation of superconductivity in doped semimetals and semiconductors, where the Fermi energy is comparable to or smaller than the characteristic phonon frequencies, is not captured by the conventional theory. In this paper, we propose a mechanism for superconductivity in ultralow-density three-dimensional Dirac materials based on the proximity to a ferroelectric quantum critical point. We derive a low-energy theory that takes into account both the strong Coulomb interaction and the direct coupling between the electrons and the soft phonon modes. We show that the Coulomb repulsion is strongly screened by the lattice polarization near the critical point even in the case of a vanishing carrier density. Using a renormalization group analysis, we demonstrate that the effective electron-electron interaction is dominantly mediated by the transverse phonon mode. We find that the system generically flows towards strong electron-phonon coupling. Hence, we propose a new mechanism to simultaneously produce an attractive interaction and suppress strong Coulomb repulsion, which does not require retardation. For comparison, we perform the same analysis for covalent crystals, where lattice polarization is negligible. We obtain qualitatively similar results, though the screening of the Coulomb repulsion is much weaker. We then apply our results to study superconductivity in the low-density limit. We find a strong enhancement of the transition temperature upon approaching the quantum critical point. Finally, we also discuss scenarios to realize a topological p-wave superconducting state in covalent crystals close to the critical point.

A nanomembrane with optical nanocavity structure was investigated employing finite difference time domain method in this paper. The nanomembrane with a typical thickness less than a few hundred nanometers can promote optical absorption sharply by introducing nanocavity structure. Geometrical parameters of the structure have a profound impact on the optical absorption of nanomembrane, which was studied in this paper. It was found that the nanocavity structure can enhance the absorption of visible light with different wavelengths by adjusting the thickness of different layers.

A new theoretical analysis explores quantum phase transitions in the absence of symmetry breaking and identifies several strange and surprising quantum critical phenomena.

We study the effects of heterostrain on moir\'e bands in twisted bilayer graphene and bilayer transition metal dichalcogenide (TMD) systems. For bilayer graphene with twist angle near $1^\circ$, we show that heterostrain significantly increases the energy separation between conduction and valence bands as well as the Dirac velocity at charge neutrality, which resolves several puzzles in scanning tunneling spectroscopy and quantum oscillation experiments at once. For bilayer TMD, we show that applying small heterostrain generally leads to flat moir\'e bands that are highly tunable., Comment: 10 pages, 11 figures

For municipal wastewater with low temperature and ammonium, conventional oxygen-limited have difficulty achieving long-term stable inhibition of nitrite oxidizing bacteria (NOB) and stable nitritation. So a partial nitrification-anaerobic ammonium oxidation integrated reactor with independent partitions was used to investigate the feasibility of adding an auto-recycling system to promote low exposure of nitrite in the aerobic zone and to inhibit the NOB activity. The results showed that nitrite produced in the aerobic zone could be timely transported to the anaerobic zone for Anammox utilization, and the nitrite nitrogen concentration was diluted to keep within 1 mg/L in the aerobic zone by the effluent recycling. NOB growth was inhibited by nitrite deficiency. The maximum nitrogen removal rate of the reactor was 0.29 kg/(m3·d), and the nitrate nitrogen production rate of NOB was controlled within 0.04 kg/(m3·d). Nitrosomonas and Candidatus Kuenenia were found as functional species of ammonia-oxidizing bacteria and Anammox bacteria, respectively.

Copper tin sulfides (CTSs) have widely been investigated as electrode materials for supercapacitors owing to their high theoretical pseudocapacitances. However, the poor intrinsic conductivity and volume change during redox reactions hindered their electrochemical performances and broad applications. In this study, carbon quantum dots (CQDs) were employed to modify CTSs. The structures and morphologies of obtained materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD revealed CTSs were composed of Cu2SnS3 and Cu4SnS4, and TEM suggested the decoration of CQDs on the surface of CTSs. With the decoration of CQDs, CTSs@CQDs showed a remarkable specific capacitance of 856 F·g−1 at 2 mV·s−1 and a high rate capability of 474 F·g−1 at 50 mV·s−1, which were superior to those of CTSs (851 F·g−1 at 2 mV·s−1 and 192 F·g−1 at 50 mV·s−1, respectively). This was mainly ascribed to incorporation of carbon quantum dots, which improved the electrical conductivity and alleviated volume change of CTSs during charge/discharge processes.

In the tip clearance flow, the dominant vortex is the tip leakage vortex (TLV), which has a significant impact on the hydraulic and cavitation performance of axial flow machinery. Thus, the suppression methods of the TLV are necessary in turbomachinery. Casing groove is an effective and economical technique among many control methods. However, its mechanism is still not completely understood. In order to reveal the effect mechanism of the casing groove on the TLV, numerical investigations of gap flow with groove configurations are carried out. A NACA0009 hydrofoil with tip gap is selected as the research object. Two typical groove types (vertical groove and horizontal groove) are applied on the solid wall respectively. Efforts are made to analyze the difference of velocity distributions between the two groove cases and the smooth wall case. Combing with the vortex stability theory, the suppression mechanisms of the two types of casing groove are distinguished and uncovered. For the vertical groove, the TLV intensity is reinforced via the secondary leakage vortex (SLV) at first, and then the supply of the axial momentum in the TLV center is cut off, leading to a less stable TLV. For the horizontal groove, the dissipation effect caused by viscosity on the TLV is strong, resulting in a weakened TLV.

In this work we explore the interplay between global symmetry and the mobility of quasiparticle excitations. We show that fractonic matter naturally appears in a three dimensional U(1) gauge theory, enriched by global U(1) and translational symmetries, via the mechanism of anyonic spin-orbital coupling. We develop a systematic understanding of such symmetry-enforced mobility restrictions in terms of the classification of U(1) gauge theories enriched by U(1) and translational symmetries. We provide a unified construction of these phases by gauging layered symmetry-protected topological phases., 13 pages, 3 figures; v2 published version

In this study, ternary Cu2SnS3 (CTS) nanostructure materials with high crystallinity were successfully prepared via a facile solvothermal method, which was followed by high-temperature treatment. The morphology of the as-synthesized samples is uniform flower-like spheres, with these spheres consisting of hierarchical nanosheets and possessing network features. Sodium storage measurements demonstrate that the annealed CTS electrodes have high initial reversible capacity (447.7 mAh&middot, g&minus, 1 at a current density of 100 mA&middot, 1), good capacity retention (200.6 mAh&middot, 1 after 50 cycles at a current density of 100 mA&middot, 1) and considerable rate capability because of their high crystallinity and unique morphology. Such good performances indicate that the high crystallinity CTS is a promising anode material for sodium ion batteries.

The lattice construction of Euclidean path integrals has been a successful approach of deriving 2+1D field theory dualities with a U$(1)$ gauge field. In this work, we generalize this lattice construction to dualities with non-Abelian gauge fields. We construct the Euclidean spacetime lattice path integral for a theory with strongly-interacting $SO(3)$ vector bosons and Majorana fermions coupled to an $SO(3)$ gauge field and derive an exact duality between this theory and the theory of a free Majorana fermion on the spacetime lattice. We argue that this lattice duality implies the desired infrared duality between the field theory with an $SO(3)$ vector critical boson coupled to an $SO(3)_1$ Chern-Simons gauge theory, and a free massless Majorana fermion in 2+1D. We also generalize the lattice construction of dualities to models with $O(3)$ gauge fields., 7 pages+Appendix

The differences in the physiological characteristics between AOB and ANAMMOX bacteria lead to suboptimal performance when used in a single reactor. In this study, aerobic and anaerobic zones with different survival environments were constructed in a single reactor to realize partitioned culture of AOB and ANAMMOX bacteria. An external air-lift reflux system was formed which used the exhaust from the aeration zone as power to return the effluent to the aeration zone. The reflux system effectively alleviated the large pH fluctuations and promoted NO2--N to rapidly use by ANAMMOX bacteria, effectively inhibiting the activity of NOB. After 95d of running, the nitrogen removal rate increased from the initial 0.21kg/(m3·d) to 3.1kg/(m3·d). FISH analyses further demonstrated that AOB and ANAMMOX bacteria acquired efficient enrichment in the corresponding zone. Thus, this type of integrative reactor may create the environments needed for the partial nitritation-ANAMMOX processing.

We propose a $d-$dimensional interacting Majorana fermion model with quenched disorder, which gives us a continuous quantum phase transition between a diffusive thermal metal phase with a finite entropy density to an insulator phase with zero entropy density. This model is based on coupled Sachdev-Ye-Kitaev model clusters, and hence has a controlled large-$N$ limit. The metal-insulator transition is accompanied by a spontaneous time-reversal symmetry breaking. We perform controlled calculations to show that the diffusion constant jumps to zero discontinuously at the metal-insulator transition, while the time-reversal symmetry breaking order parameter increases continuously., Comment: 11 pages

We ask whether a local Hamiltonian with a featureless (fully gapped and nondegenerate) ground state could exist in certain quantum spin systems. We address this question by mapping the vicinity of certain quantum critical point (or gapless phase) of the $d-$dimensional spin system under study to the boundary of a $(d+1)-$dimensional bulk state, and the lattice symmetry of the spin system acts as an on-site symmetry in the field theory that describes both the selected critical point of the spin system, and the corresponding boundary state of the $(d+1)-$dimensional bulk. If the symmetry action of the field theory is nonanomalous, i.e. the corresponding bulk state is a trivial state instead of a bosonic symmetry protected topological (SPT) state, then a featureless ground state of the spin system is allowed; if the corresponding bulk state is indeed a nontrivial SPT state, then it likely excludes the existence of a featureless ground state of the spin system. From this perspective we identify the spin systems with SU($N$) and SO($N$) symmetries on one, two and three dimensional lattices that permit a featureless ground state. We also verify our conclusions by other methods, including an explicit construction of these featureless spin states., Comment: 15 pages, 5 figures

In this work we propose a theory for the deconfined quantum critical point (DQCP) for spin-1/2 systems on a triangular lattice, which is a direct unfine-tuned quantum phase transition between the standard ``$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$'' noncollinear antiferromagnetic order (or the so-called ${120}^{\ensuremath{\circ}}$ state) and the ``$\sqrt{12}\ifmmode\times\else\texttimes\fi{}\sqrt{12}$'' valence solid bond (VBS) order, both of which are very standard ordered phases often observed in numerical simulations. This transition is beyond the standard Landau-Ginzburg paradigm and is also fundamentally different from the original DQCP theory on the square lattice due to the very different structures of both the magnetic and VBS order on frustrated lattices. We first propose a topological term in the effective-field theory that captures the ``intertwinement'' between the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ antiferromagnetic order and the $\sqrt{12}\ifmmode\times\else\texttimes\fi{}\sqrt{12}$ VBS order. Then using a controlled renormalization-group calculation, we demonstrate that an unfine-tuned direct continuous DQCP exists between the two ordered phases mentioned above. This DQCP is described by the ${N}_{f}=4$ quantum electrodynamics (QED) with an emergent PSU(4)=SU(4)/${Z}_{4}$ symmetry only at the critical point. The aforementioned topological term is also naturally derived from the ${N}_{f}=4$ QED. We also point out that physics around this DQCP is analogous to the boundary of a $3d$ bosonic symmetry- protected topological state with only on-site symmetries.

We study a series of perturbations on the Sachdev-Ye-Kitaev (SYK) model. We show that the chaotic non-Fermi liquid phase described by the ordinary $q = 4$ SYK model has marginally relevant/irrelevant (depending on the sign of the coupling constants) four-fermion perturbations allowed by symmetry. Changing the sign of one of these four-fermion perturbations leads to a continuous chaotic-nonchaotic quantum phase transition of the system accompanied by a spontaneous time-reversal symmetry breaking. Starting with the SYK$_q$ model with a $q-$fermion interaction, similar perturbations can lead to a series of new interacting conformal field theory fixed points., Comment: 11 pages, 8 figures

In the last few years a lot of exotic and anomalous topological phases were constructed by proliferating the vortexlike topological defects on the surface of the $3d$ topological insulator (TI) [Fidkowski et al., Phys. Rev. X 3, 041016 (2013); Chen et al., Phys. Rev. B 89, 165132 (2014); Bonderson et al., J. Stat. Mech. (2013) P09016; Wang et al., Phys. Rev. B 88, 115137 (2013); Metlitski et al., Phys. Rev. B 92, 125111 (2015)]. In this work, rather than considering topological phases at the boundary, we will study quantum critical points driven by vortexlike topological defects. In general, we will discuss a $(2+1)d$ quantum phase transition described by the following field theory: $\mathcal{L}=\overline{\ensuremath{\psi}}{\ensuremath{\gamma}}_{\ensuremath{\mu}}({\ensuremath{\partial}}_{\ensuremath{\mu}}\ensuremath{-}i{a}_{\ensuremath{\mu}})\ensuremath{\psi}+|({\ensuremath{\partial}}_{\ensuremath{\mu}}\ensuremath{-}ik{a}_{\ensuremath{\mu}}){\ensuremath{\phi}|}^{2}+{r|\ensuremath{\phi}|}^{2}+g{|\ensuremath{\phi}|}^{4}$, with tuning parameter $r$, arbitrary integer $k$, Dirac fermion $\ensuremath{\psi}$, and complex scalar bosonic field $\ensuremath{\phi}$, which both couple to the same $(2+1)d$ dynamical noncompact U(1) gauge field ${a}_{\ensuremath{\mu}}$. The physical meaning of these quantities/fields will be explained in the text. Making use of the new duality formalism developed in [Metlitski et al., Phys. Rev. B 93, 245151 (2016); Wang et al., Phys. Rev. X 5, 041031 (2015); Wang et al., Phys. Rev. B 93, 085110 (2016); D. T. Son, Phys. Rev. X 5, 031027 (2015)], we demonstrate that this quantum critical point has a quasi-self-dual nature. And at this quantum critical point, various universal quantities such as the electrical conductivity and scaling dimension of gauge-invariant operators, can be calculated systematically through a $1/{k}^{2}$ expansion, based on the observation that the limit $k\ensuremath{\rightarrow}+\ensuremath{\infty}$ corresponds to an ordinary $3d XY$ transition.

We show that the out-of-time-order correlation (OTOC) $ \langle W(t)^\dagger V(0)^\dagger W(t)V(0)\rangle$ in many-body localized (MBL) and marginal MBL systems can be efficiently calculated by the spectrum bifurcation renormalization group (SBRG). We find that in marginal MBL systems, the scrambling time $t_\text{scr}$ follows a stretched exponential scaling with the distance $d_{WV}$ between the operators $W$ and $V$: $t_\text{scr}\sim\exp(\sqrt{d_{WV}/l_0})$, which demonstrates Sinai diffusion of quantum information and the enhanced scrambling by the quantum criticality in non-chaotic systems., Comment: 6 pages, 4 figures

We propose a series of simple $2d$ lattice interacting fermion models that we demonstrate at low energy describe bosonic symmetry protected topological (SPT) states and quantum phase transitions between them. This is because due to interaction the fermions are gapped both at the boundary of the SPT states and at the bulk quantum phase transition, thus these models at low energy can be described completely by bosonic degrees of freedom. We show that the bulk of these models is described by a Sp($N$) principal chiral model with a topological $\Theta$-term, whose boundary is described by a Sp($N$) principal chiral model with a Wess-Zumino-Witten term at level-1. The quantum phase transition between SPT states in the bulk is tuned by a particular interaction term, which corresponds to tuning $\Theta$ in the field theory, and the phase transition occurs at $\Theta = \pi$. The simplest version of these models with $N=1$ is equivalent to the familiar O(4) nonlinear sigma model (NLSM) with a topological term, whose boundary is a $(1+1)d$ conformal field theory with central charge $c = 1$. After breaking the O(4) symmetry to its subgroups, this model can be viewed as bosonic SPT states with U(1), or $Z_2$ symmetries, etc. All these fermion models including the bulk quantum phase transitions can be simulated with determinant Quantum Monte Carlo method without the sign problem. Recent numerical results strongly suggests that the quantum disordered phase of the O(4) NLSM with precisely $\Theta = \pi$ is a stable $(2+1)d$ conformal field theory (CFT) with gapless bosonic modes., Comment: 10 pages, 3 figures

We demonstrate that the anyon statistics and three-loop statistics of various 2d and 3d topological phases can be derived using semiclassical nonlinear Sigma model field theories with a topological $\Theta$-term. In our formalism, the braiding statistics has a natural geometric meaning: The braiding process of anyons or loops leads to a nontrivial field configuration in the space-time, which will contribute a braiding phase factor due to the $\Theta$-term., Comment: 4 pages, 3 figures

A 3d symmetry protected topological phase, by definition must have symmetry protected nontrivial boundary states, namely its 2d boundary must be either gapless or degenerate. In this work we demonstrate that once we couple a 3d SPT phase to a lattice dynamical Z2 gauge field, in many cases the Z2 vison loop excitation (line defect) can be viewed as a "1d boundary" of the 3d SPT phase, and this line defect is guaranteed to have gapless or degenerate spectrum, which is also protected by the symmetry of the SPT phase., Comment: 5 pages, 2 figures

We demonstrate the following conclusion: If $|\Psi\rangle$ is a $1d$ or $2d$ nontrivial short range entangled state, and $|\Omega \rangle$ is a trivial disordered state defined on the same Hilbert space, then the following quantity (so called strange correlator) $C(r, r^\prime) = \frac{\langle \Omega|\phi(r) \phi(r^\prime) | \Psi\rangle}{\langle \Omega| \Psi\rangle}$ either saturates to a constant or decays as a power-law in the limit $|r - r^\prime| \rightarrow +\infty$, even though both $| \Omega\rangle$ and $| \Psi\rangle$ are quantum disordered states with short-range correlation. $\phi(r)$ is some local operator in the Hilbert space. This result is obtained based on both field theory analysis, and also an explicit computation of $C(r, r^\prime)$ for four different examples: $1d$ Haldane phase of spin-1 chain, $2d$ quantum spin Hall insulator with a strong Rashba spin-orbit coupling, $2d$ spin-2 AKLT state on the square lattice, and the $2d$ bosonic symmetry protected topological phase with $Z_2$ symmetry. This result can be used as a diagnosis for short range entangled states in $1d$ and $2d$. A possible diagnosis for $3d$ short range entangled states is also proposed., Comment: 5 pages, 5 figures