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In the past decades, tremendous efforts have been made towards understanding the exotic physics emerging from competition between various ordering tendencies in strongly correlated systems. Employing state-of-the-art quantum Monte-Carlo simulation, we investigate an interacting SU($N$) fermionic model with varying interaction strength and value of $N$, and unveil the ground-state phase diagram of the model exhibiting a plethora of exotic phases. For small value of $N$, namely $N=2,3$, the ground state is antiferromagnetic (AFM) phase, whereas in the large-$N$ limit, valence bound solid (VBS) order is dominant. For the intermediate value of $N$ such as $N=4$, remarkably, our study reveals distinct VBS orders appear in the weak and strong coupling regimes. More fantastically, the competition between staggered and columnar VBS ordering tendencies gives rise to a Mott insulating phase without spontaneously symmetry breaking (SSB), existing in a large interacting parameter regime, which is consistent with a gapped quantum spin liquid. Our study not only provides a platform to investigate the fundamental physics of quantum many-body systems, but also offers a novel route towards searching for exotic states of matter such as quantum spin liquid in realistic quantum materials., 4.5 pages, 5 figures plus supplementary materials

Structural deformation monitoring is vital to the safety of concrete structures. However, the distributed deformation of structures cannot be easily obtained using existing monitoring methods in civil engineering. To this end, this paper proposes a method to estimate the continuous deformation of concrete beams by utilizing the distributed optical fiber monitoring technology. In this method, optical fibers and a total station are used to obtain the strain and deformation distribution curves of a concrete beam, respectively. Subsequently, these curves are inputted to a back propagation network as training samples to learn their relationships. The results show that the deformation value of trained neural network is very close to that of the total station, with a maximum error of only 2.7% (0.3 mm). The linear regression analysis shows a goodness of fit R2 greater than 0.98, which confirms the reliability of the simulations results.

We recently unveiled that antiferromagnetism (AFM) order can be dominantly induced by the bond Su-Schrieffer-Heeger (SSH) electron-phonon coupling (EPC), which is beyond the conventional wisdom that AFM order is usually driven by strong Coulomb interactions. Nevertheless, many aspects of the interplay between EPC and strong electronic interactions on AFM ordering remains unexplored. Here, we investigate the Su-Schrieffer-Heeger-Hubbard (SSHH) model with bond SSH phonons and onsite Hubbard interactions by large-scale quantum Monte-Carlo (QMC) simulations and obtain its ground-state phase diagram for various Hubbard interactions and EPC strength at half filling. Our results show that Hubbard interactions further enhance EPC-induced AFM, especially for small phonon frequency or in adiabatic limit, the regime most relevant to various quantum materials. This could shed further light to understanding the cooperative effect between EPC and electronic correlations in quantum materials., Comment: 4 pages plus supplemental material, 5 figures

The prediction of the mechanical properties of hot-rolled strips is a very complex, highly dimensional and nonlinear problem, and the published models might lack reliability, practicability and generalization. Thus, a new model was proposed for predicting the mechanical properties of hot-rolled strips by deep learning. First, the one-dimensional numerical data were transformed into two-dimensional data for expressing the complex interaction between the influencing factors. Subsequently, a new convolutional network was proposed to establish the prediction model of tensile strength of hot-rolled strips, and an improved inception module was introduced into this network to abstract features from different scales. Many comparative experiments were carried out to find the optimal network structure and its hyperparameters. Finally, the prediction experiments were carried out on different models to evaluate the performance of the new convolutional network, which includes the stepwise regression, ridge regression, support vector machine, random forest, shallow neural network, Bayesian neural network, deep feed-forward network and improved LeNet-5 convolutional neural network. The results show that the proposed convolutional network has better prediction accuracy of the mechanical properties of hot-rolled strips compared with other models.

Antiferromagnetism (AFM) such as Néel ordering is often closely related to Coulomb interactions such as Hubbard repulsion in two-dimensional (2D) systems. Whether Néel AFM ordering in two dimensions can be dominantly induced by electron-phonon couplings (EPC) has not been completely understood. Here, by employing numerically exact sign-problem-free quantum Monte Carlo (QMC) simulations, we show that bond Su-Schrieffer-Heeger (SSH) phonons with frequency ω and EPC constant λ can induce AFM ordering for a wide range of phonon frequency ωω_{c}. For ωω_{c}, a valence-bond-solid (VBS) order appears and there is a direct quantum phase transition between VBS and AFM phases at ω_{c}. The phonon mechanism of the AFM ordering is related to the fact that SSH phonons directly couple to electron hopping whose second-order process can induce an effective AFM spin exchange. Our results shall shed new light on understanding AFM ordering in correlated quantum materials.

We present a theoretical framework for understanding the behavior of the normal and superconducting states of overdoped cuprate high temperature superconductors in the vicinity of the doping-tuned quantum superconductor-to-metal transition. The key ingredients on which we focus are d-wave pairing, a flat antinodal dispersion, and disorder. Even for homogeneous disorder, these lead to effectively granular superconducting correlations and a superconducting transition temperature determined in large part by the superfluid stiffness rather than the pairing scale.

Author(s): He, Y; Chen, SD; Li, ZX; Zhao, D; Song, D; Yoshida, Y; Eisaki, H; Wu, T; Chen, XH; Lu, DH; Meingast, C; Devereaux, TP; Birgeneau, RJ; Hashimoto, M; Lee, DH; Shen, ZX | Abstract: Fluctuating superconductivity—vestigial Cooper pairing in the resistive state of a material—is usually associated with low dimensionality, strong disorder, or low carrier density. Here, we report single-particle spectroscopic, thermodynamic and magnetic evidence for persistent superconducting fluctuations in the heavily hole-doped cuprate superconductor () despite the high carrier density. With a sign-problem-free quantum MontenCarlo calculation, we show how a partially flat band at can help enhance superconducting phase fluctuations. Finally, we discuss the implications of an anisotropic band structure on the phase-coherence-limited superconductivity in overdoped cuprates and other superconductors.

BACKGROUND The treatment outcome of transarterial chemoembolization (TACE) in unresectable hepatocellular carcinoma (HCC) varies greatly due to the clinical heterogeneity of the patients. Therefore, several prognostic systems have been proposed for risk stratification and candidate identification for first TACE and repeated TACE (re-TACE). AIM To investigate the correlations between prognostic systems and radiological response, compare the predictive abilities, and integrate them in sequence for outcome prediction. METHODS This nationwide multicenter retrospective cohort consisted of 1107 unresectable HCC patients in 15 Chinese tertiary hospitals from January 2010 to May 2016. The Hepatoma Arterial-embolization Prognostic (HAP) score system and its modified versions (mHAP, mHAP2 and mHAP3), as well as the six-and-twelve criteria were compared in terms of their correlations with radiological response and overall survival (OS) prediction for first TACE. The same analyses were conducted in 912 patients receiving re-TACE to evaluate the ART (assessment for re-treatment with TACE) and ABCR (alpha-fetoprotein, Barcelona Clinic Liver Cancer, Child-Pugh and Response) systems for post re-TACE survival (PRTS). RESULTS All the prognostic systems were correlated with radiological response achieved by first TACE, and the six-and-twelve criteria exhibited the highest correlation (Spearman R = 0.39, P = 0.026) and consistency (Kappa = 0.14, P = 0.019), with optimal performance by area under the receiver operating characteristic curve of 0.71 [95% confidence interval (CI): 0.68-0.74]. With regard to the prediction of OS, the mHAP3 system identified patients with a favorable outcome with the highest concordance (C)-index of 0.60 (95%CI: 0.57-0.62) and the best area under the receiver operating characteristic curve at any time point during follow-up; whereas, PRTS was well-predicted by the ABCR system with a C-index of 0.61 (95%CI: 0.59-0.63), rather than ART. Finally, combining the mHAP3 and ABCR systems identified candidates suitable for TACE with an improved median PRTS of 36.6 mo, compared with non-candidates with a median PRTS of 20.0 mo (log-rank test P < 0.001). CONCLUSION Radiological response to TACE is closely associated with tumor burden, but superior prognostic prediction could be achieved with the combination of mHAP3 and ABCR in patients with unresectable liver-confined HCC.

The recent discovery of the interfacial superconductivity (SC) of the Bi2Te3/Fe1+yTe heterostructure has attracted extensive studies due to its potential as a novel platform for trapping and controlling Majorana fermions. Here we present studies of another topological insulator (TI)/Fe1+yTe heterostructure, Sb2Te3/Fe1+yTe, which also enjoys an interfacial two-dimensional SC. The results of transport measurements support that the reduction of excess Fe concentration of the Fe1+yTe layer not only increases the fluctuation of its antiferromagnetic (AFM) order but also enhances the quality of the SC of this heterostructure system. On the other hand, the interfacial SC of this heterostructure was found to have a wider-ranging TI-layer thickness dependence than that of the Bi2Te3/Fe1+yTe heterostructure, which is believed to be attributed to the much higher bulk conductivity of Sb2Te3 that enhances indirect coupling between its top and bottom topological surface states (TSSs). Our results provide the evidence of the interplay among the AFM order, itinerant carries from the TSSs and the induced interfacial SC of the TI/Fe1+yTe heterostructure system., 28 pages, 5 figures

In this paper, we apply the K-theory to classify topological trivial fermionic phases which, nonetheless, host symmetry-protected non-trivial defects. An important implication of our work is that the existence of Majorana zero mode in the vortex core is neither a necessary nor a sufficient condition for the superconductor in question being topologically non-trivial.

Reliable simulations of correlated quantum systems, including high-temperature superconductors and frustrated magnets, are increasingly desired nowadays to further understanding of essential features in such systems. Quantum Monte Carlo (QMC) is a unique numerically-exact and intrinsically-unbiased method to simulate interacting quantum many-body systems. More importantly, when QMC simulations are free from the notorious fermion-sign problem, they can reliably simulate interacting quantum models with large system size and low temperature to reveal low-energy physics such as spontaneously-broken symmetries and universal quantum critical behaviors. Here, we concisely review recent progresses made in developing new sign-problem-free QMC algorithms, including those employing Majorana representation and those utilizing hot-spot physics. We also discuss applications of these novel sign-problem-free QMC algorithms in simulations of various interesting quantum many-body models. Finally, we discuss possible future directions of designing sign-problem-free QMC methods., Comment: Invited by Annual Review of Condensed Matter Physics, 21 pages

Osteoarthritis (OA), characterized by chondrocyte apoptosis and disturbance of the balance between catabolism and anabolism of the extracellular matrix (ECM), is the most common age-related degenerative joint disease worldwide. As sleep has been found to be beneficial for cartilage repair, and circular RNAs (circRNAs) have been demonstrated to be involved in the pathogenesis of OA, we performed RNA sequencing (RNA-seq), and found circRNA3503 was significantly increased after melatonin (MT)-induced cell sleep. Upregulation of circRNA3503 expression completely rescued the effects of interleukin-1β (IL-1β), which was used to simulate OA, on apoptosis, ECM degradation- and synthesis-related genes. Mechanistically, circRNA3503 acted as a sponge of hsa-miR-181c-3p and hsa-let-7b-3p. Moreover, as we previously showed that small extracellular vesicles (sEVs) derived from synovium mesenchymal stem cells (SMSCs) can not only successfully deliver nucleic acids to chondrocytes, but also effectively promote chondrocyte proliferation and migration, we assessed the feasibility of sEVs in combination with sleep-related circRNA3503 as an OA therapy. We successfully produced and isolated circRNA3503-loaded sEVs (circRNA3503-OE-sEVs) from SMSCs. Then, poly(D,l-lactide)-b-poly(ethylene glycol)-b-poly(D,l-lactide) (PDLLA-PEG-PDLLA, PLEL) triblock copolymer gels were used as carriers of sEVs. Through in vivo and in vitro experiments, PLEL@circRNA3503-OE-sEVs were shown to be a highly-effective therapeutic strategy to prevent OA progression. Through multiple pathways, circRNA3503-OE-sEVs alleviated inflammation-induced apoptosis and the imbalance between ECM synthesis and ECM degradation by acting as a sponge of hsa-miR-181c-3p and hsa-let-7b-3p. In addition, circRNA3503-OE-sEVs promoted chondrocyte renewal to alleviate the progressive loss of chondrocytes. Our results highlight the potential of PLEL@circRNA3503-OE-sEVs for preventing OA progression., Graphical abstract Image 1, Highlights • CircRNA3503 alleviated apoptosis and the imbalance between ECM synthesis and ECM degradation. • Wnt5a/b carried by sEVs promoted chondrocyte renewal to alleviate the progressive loss of chondrocytes. • PDLLA-PEG-PDLLA (PLEL) triblock copolymer gels showed good performance in slow release of sEVs. • PLEL@circRNA3503-OE-sEVs showed potential to prevent OA progression.

Temporary shorings are necessary for the stabilization of the tunnels with large cross-sections that are excavated using the New Austrian tunnelling method. The dismantling of the temporary shoring during the process of secondary lining construction would be a very serious threat to the safety of the tunnel. Therefore, in this work, a field observation was made based on distributed optical fiber sensing monitoring technology in order to determine the deformation behavior of the tunnel and to identify the most influential steps of dismantlement. The study is carried out during the tunnel’s temporary shoring dismantling stage. The performance of the tunnel during every dismantling stage was analyzed based on the monitoring results using the finite element numerical simulation method. Based on the analysis results, the settlement of the tunnel was estimated through the strain curve that was obtained by using optical fiber. Furthermore, the study results showed that the continuous removal at the bottom of the shoring of the tunnel weakens the vertical support force at the bottom of the tunnel and thereby resulting in large settlement variation in all the dismantling steps. The highest value of the settlement variation obtained during the analysis is 5.7 mm, and the corresponding tensile strain variation of the crown is 50 μe. Furthermore, the results showed that it is feasible to use the optical fiber to estimate the settlement of the tunnel. The max deviation obtained was 0.9 mm and the results were compared with the results of a total station. The study results of this research are applicable to the tunnels that were excavated using the New Austrian tunnelling method and have temporary shorings.

We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid. Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid. Both phases have full spin gaps and exhibit power-law superconducting pair correlation. The Cooper pair symmetry is singlet d xy in the non-trivial phase and triplet S z = 0 in the trivial phase. The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary, and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned. As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes. We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.

Tunnel deformation monitoring is an important process for ensuring the safety of the tunnel structure. This study presents a method for sensing tunnel cross-section deformation based on distributed fiber optic sensing and a neural network. To verify the feasibility of the proposed method, a laboratory test is conducted on a tunnel model made of polymethyl methacrylate. The test results confirm that the proposed method can accurately obtain the deformation of the tunnel structure, with a maximum deviation of 5.7%. Based on this result, a field application trial is conducted in a section of an actual subway tunnel to further verify the effectiveness of the method. The field observation result confirms the feasibility of applying the proposed method to tunnel cross-section deformation monitoring.

Forkhead box protein M1 (FoxM1) is aberrantly expressed in several types of human malignancy, and serves an important role in tumor metastasis. Epithelial‑mesenchymal transition (EMT) of cancer cells has been associated cancer metastasis; however, the implication of FoxM1 in EMT and its putative roles in the regulation of cancer metastasis remain to be elucidated. In the present study, the expression of FoxM1, Snai1 and E‑cadherin in hepatocellular carcinoma (HCC) cell lines with various metastatic potentials, and in normal liver cells, was investigated using western blot analysis and reverse transcription‑quantitative polymerase chain reaction. The effects of FoxM1 on the invasive and migratory capabilities of HCC cells were evaluated using wound healing and Transwell migration assays. The present results demonstrated that FoxM1 expression was significantly upregulated in HCC cells compared with in normal hepatocytes (P

Mining deformation of roof strata is the main cause of methane explosion, water inrush, and roof collapse accidents amid underground coal mining. To ensure the safety of coal mining, the distributed optical fiber sensor (DFOS) technology has been applied in the 150,313 working face by Yinying Coal Mine in Shanxi Province, north China to monitor the roof strata movement, so as to grasp the movement law of roof strata and make it serve for production. The optical fibers are laid out in the holes drilled through the overlying strata on the roadway roof and BOTDR technique is utilized to carry out the on-site monitoring. Prior to the on-site test, the coupling test of the fiber strain in the concrete anchorage, the calibration test of the fiber strain coefficient of the 5-mm steel strand (SS) fiber, and the test of the strain transfer performance of the SS fiber were carried out in the laboratory. The approaches for fiber laying-out in the holes and fiber&rsquo, s spatial positioning underground the coal mine have been optimized in the field. The indoor test results show that the high-strength SS optical fiber has a high strain transfer performance, which can be coupled with the concrete anchor with uniform deformation. This demonstrated the feasibility of SS fiber for monitoring strata movement theoretically and experimentally, and the law of roof strata fracturing and collapse is obtained from the field test results. This paper is a trial to study the whole process of dynamic movement of the deformation of roof strata. Eventually the study results will help Yinying Coal Mine to optimize mining design, prevent coal mine accidents, and provide detailed test basis for DFOS monitoring technique of roof strata movement.

Author(s): Li, ZX; Cohen, ML; Lee, DH | Abstract: We study strong electron-phonon interacting systems where the geometry of the crystalline lattice frustrates the formation of charge order. Our results show that under such condition, high-Tc superconductivity can occur in a wide range of electron-phonon coupling strengths. This result is obtained by studying the Holstein model on triangular lattice using sign-problem-free quantum Monte Carlo method.

The interplay between disorder and superconductivity is a subtle and fascinating phenomenon in quantum many-body physics. Conventional superconductors are insensitive to dilute non-magnetic impurities, known as Anderson’s theorem1. Destruction of superconductivity and even superconductor–insulator transitions2–10 occur in the regime of strong disorder. Hence, disorder-enhanced superconductivity is rare and has been observed only in some alloys or granular states11–17. Owing to the entanglement of various effects, the mechanism of enhancement is still under debate. Here, we report a well-controlled disorder effect in the recently discovered monolayer NbSe2 superconductor. The superconducting transition temperatures of NbSe2 monolayers are substantially increased by disorder. Realistic theoretical modelling shows that the unusual enhancement possibly arises from the multifractality18,19 of electron wavefunctions. This work provides experimental evidence of the multifractal superconducting state. Disorder present in monolayer NbSe2 is found to be able to enhance its superconductivity. A systematic study reveals the origin—disorder-induced multifractality of the electron wavefunctions strengthens the local interactions.

For tunnels with large cross-sections, demolition of the temporary shoring of the tunnel can pose a very serious threat to the safety of the structure; Therefore it is very important to ascertain the deformation behavior of the tunnel in this stage. In this study, a tunnel settlement inversion model, based on the strain measurements of distributed optical fiber, has been proposed and the feasibility of the model has been verified by laboratory tests. Based on field observations, the strain distribution characteristics of the optical fibers and the variations in the mechanical properties of the tunnel were analyzed, taking the demolition process into consideration. The results of the monitoring indicated that demolition of the bottom shoring will cause large and uneven crown settlements; this is because this step will weaken the vertical supporting force at the bottom of the arch. Besides, continuous removal of the bottom shoring of the tunnel can result in large settlement and deformation of the crown, which should be pay attention in this stage. The settlement curve of the tunnel has also shown that the strain distribution of the optical fibers was able to reflect the performance of the tunnel in the demolition process of its temporary shorings.

Monolayer FeSe films grown on SrTiO3 (STO) substrate show superconducting gap-opening temperatures (Tc) which are almost an order of magnitude higher than those of the bulk FeSe and are highest among all known Fe-based superconductors. Angle-resolved photoemission spectroscopy (ARPES) observed "replica bands" suggesting the importance of the interaction between FeSe electrons and STO phonons. These facts rejuvenated the quest for Tc enhancement mechanisms in iron-based, especially iron-chalcogenide, superconductors. Here, we perform the first numerically-exact sign-problem-free quantum Monte Carlo simulations to iron-based superconductors. We (i) study the electronic pairing mechanism intrinsic to heavily electron doped FeSe films, and (ii) examine the effects of electron-phonon interaction between FeSe and STO as well as nematic fluctuations on Tc. Armed with these results, we return to the question "what makes the Tc of monolayer FeSe on SrTiO3 so high?" in the conclusion and discussions., Comment: 5.2 pages; Highlight of this work by Steven A. Kivelson, arXiv:1605.04378, has been published in Science Bulletin [Sci. Bull. 61, 911 (2016) http://link.springer.com/article/10.1007/s11434-016-1101-3]

In recent years, distributed fiber optic sensing (DFOS) has been widely used for structural deformation monitoring. Conventional deformation monitoring methods using DFOS have a limitation in that they are based on the conventional assumptions in continuum mechanics such as uniformity and continuity. These methods are unsuitable for cracked concrete structures that exhibit discontinuity (discrete body). This paper proposes an advanced neural network method that can accurately measure the deformation of cracked concrete structures. The basic principle of the method is introduced, and its performance is validated by conducting a concrete beam loading test. Subsequently, the deformation calculation results obtained using the proposed method are compared with those obtained using the conventional conjugate beam method. The two methods could accurately estimate the deformation of the concrete beam before crack formation. The proposed neural network method could accurately determine the deformation with a maximum error of only 4.3% at all loading levels even after crack formation, whereas the conventional method exhibited a maximum error of 33.6% in this stage. The test results confirm the advantages of the proposed method in making accurate estimations of the deformation in concrete structures with cracks.

When using distributed optical fibers for structural health monitoring, in order to ensure the survival rate of the optical fibers, it is usually necessary to insert the optical fibers into the structure for protection. The coupling performance between the optical fibers and the structure determines the accuracy of the monitoring results. In order to explore the strain transfer law of optical fibers in structures, a strain transfer model based on shear lag theory was established. From analyzing the strain transfer mechanism of optical fibers in structures, the expression of strain transfer efficiency of optical fibers was deduced and the accuracy of the deduced results was verified by comparing with the numerical results. Based on BOFDA technology, two groups of loading tests were carried out to test the strain transfer effect of distributed optical fibers embedded in the test beam. The results have shown that the two ends of the structure were low-efficiency strain transfer zones of optical fibers, which could not fully transfer the strain of the test beam. The middle part of the structure was high-efficiency strain transfer zone of optical fibers, which could completely transfer the strain of the structure. The experimental results were basically consistent with the theoretical deduction. The above research can provide reference for the application of distributed optical fiber technology in engineering structure monitoring.

The prognosis for osteosarcoma (OS) continues to be unsatisfactory due to tumor recurrence as a result of metastasis and drug resistance. Several studies have shown that Ewing sarcoma associated transcript 1 (EWSAT1) plays an important role in the progression of OS. Exosomes (Exos) act as important carriers in intercellular communication and play an important role in the tumor microenvironment, especially in tumor-induced angiogenesis. Nonetheless, the specific mechanism via which EWSAT1 and Exos regulate OS progression is unknown, and whether they can be effective therapeutic targets also requires verification. Hence, in this study, it is aimed to investigate the mechanisms of action of EWSAT1 and Exos. EWSAT1 significantly promotes proliferation, migration, colony formation, and survival of OS. EWSAT1 regulates OS-induced angiogenesis via two mechanisms, called the "double stacking effect," which is a combination of the increase in sensitivity/reactivity of vascular endothelial cells triggered by Exos-carrying EWSAT1, and the EWSAT1-induced increase in angiogenic factor secretion. In vivo experiments further validates the "double stacking effect" and shows that EWSAT1-KD effectively inhibits tumor growth in OS. The above observations indicate that EWSAT1 can be used as not only a potential diagnostic and prognostic marker, but also as a precise therapeutic target for OS.

According to the Landau criterion, a phase transition should be first order when cubic terms of order parameters are allowed in its effective Ginzburg-Landau free energy. Recently, it was shown by renormalization-group (RG) analysis that continuous transition can happen at putatively first-order ${Z}_{3}$ transitions in two-dimensional (2D) Dirac semimetals and such non-Landau phase transitions were dubbed ``fermion-induced quantum critical points'' (FIQCPs) [Z.-X. Li, Y.-F. Jiang, S.-K. Jian, and H. Yao, Nat. Commun. 8, 314 (2017)]. The RG analysis, controlled by the $1/N$ expansion with $N$ the number of flavors of four-component Dirac fermions, shows that the FIQCP occurs for $N\ensuremath{\ge}{N}_{c}$. Previous quantum Monte Carlo simulations of a microscopic model of $\mathrm{SU}(N$) fermions on the honeycomb lattice showed that the FIQCP occurs at the transition between Dirac semimetals and Kekule valence bond solids for $N\ensuremath{\ge}2$. However, the precise value of the lower bound ${N}_{c}$ has not been established. Especially, the case of $N=1$ has not been explored by studying microscopic models so far. Here, by introducing a generalized $\mathrm{SU}(N$) fermion model with $N=1$ (namely, spinless fermions on the honeycomb lattice), we perform large-scale sign-problem-free Majorana quantum Monte Carlo simulations and find convincing evidence of the FIQCP for $N=1$. Consequently, our results suggest that the FIQCP can occur in 2D Dirac semimetals for all positive integers $N\ensuremath{\ge}1$.

Supersymmetry is shown to emerge at the superconducting quantum criticality of a lattice model realizing a single Dirac cone., No definitive evidence of spacetime supersymmetry (SUSY) that transmutes fermions into bosons and vice versa has been revealed in nature so far. Moreover, the question of whether spacetime SUSY in 2 + 1 and higher dimensions can emerge in generic lattice microscopic models remains open. Here, we introduce a lattice realization of a single Dirac fermion in 2 + 1 dimensions with attractive interactions that preserves both time-reversal and chiral symmetries. By performing sign problem–free determinant quantum Monte Carlo simulations, we show that an interacting single Dirac fermion in 2 + 1 dimensions features a superconducting quantum critical point (QCP). We demonstrate that the N=2 spacetime SUSY in 2 + 1 dimensions emerges at the superconducting QCP by showing that the fermions and bosons have identical anomalous dimensions 1/3, a hallmark of the emergent SUSY. We further show some experimental signatures that may be measured to test such emergent SUSY in candidate systems.

We study the electron and phonon spectral functions as well as superconductivity for a two dimensional electron gas couped to dipolar phonons via small-momentum transfer scattering. The results reported here are obtained through sign-problem-free quantum Monte-Carlo simulation. Hence aside from modeling there is no further approximations. Our results can be relevant to the high-temperature superconductor at the interface between a unit-cell-thick FeSe and SrTiO3., Comment: 5 pages + supplemental materials,4 figures; comments are welcome

The robustness of helical edge states in two-dimensional (2D) topological insulators (TIs) against strong interactions remains an intriguing issue. Here, by performing a sign-free quantum Monte Carlo (QMC) simulation of the Kane-Mele-Hubbard-Rashba model which describes an interacting 2D TI with two-particle backscattering on the edges, we verify that the gapless helical edge states are robust against a finite range of two-particle backscattering when the Coulomb repulsion is not strong. However, when the Coulomb repulsion is strong enough, the helical edge states can be gapped by infinitesimal two-particle backscattering, resulting in an edge magnetic order. We further reveal the universal properties of the magnetic edge quantum critical point (EQCP). At magnetic domain walls on edges, we find that a fractionalized charge of $e/2$ emerges. Implications of our results to recent transport experiments in an InAs/GaSb quantum well, which is a 2D TI with strong interactions, will also be discussed.

Understanding the mechanism of Cooper pairing amounts to determining the effective interaction that operates at low energies. Efforts to achieve such a goal for superconducting materials, especially strongly correlated ones, from both bottom-up and top-down approaches, have been plagued by having to use uncontrolled approximations. Here, we perform large-scale, numerically exact, sign-problem-free zero-temperature quantum Monte Carlo simulations on an effective theory based on ``hot spots'' plus fluctuating collective modes. Because hot spots are clearly identified by angle-resolved photoemission spectroscopy for electron-doped cuprates, we focus our attention on such materials. Our goal is to determine the minimum effective action that can describe the observed superconductivity and charge-density wave. The results suggest that antiferromagnetic fluctuation alone is not sufficient---the effective action needs to be amended with nematic fluctuations. We believe that our results address the pairing mechanism of high-${T}_{c}$ superconductivity in electron-doped cuprates, and they shed light on the pairing mechanism of hole-doped cuprates.

Proposed as a fundamental symmetry describing our universe, spacetime supersymmetry (SUSY) has not been discovered yet in nature. Nonetheless, it has been predicted that SUSY may emerge in low-energy physics of quantum materials such as topological superconductors and Weyl semimetals. Here, by performing state-of-the-art sign-problem-free Majorana quantum Monte Carlo (QMC) simulations of an interacting 2D topological superconductor, we show convincing evidences that the N=1 SUSY emerges at its edge quantum critical point (EQCP) while its bulk remains gapped and topologically nontrivial. Remarkably, near the EQCP, we find that the edge Majorana fermion acquires a mass which is identical with that of its bosonic superpartner. To the best of our knowledge, this is the first observation that fermions and bosons have equal dynamically-generated masses, a hallmark of emergent SUSY. We further discuss experimental signatures of such EQCP and the associated edge SUSY., Published version in PRL

A unified theory of quantum critical points beyond the conventional Landau–Ginzburg–Wilson paradigm remains unknown. According to Landau cubic criterion, phase transitions should be first-order when cubic terms of order parameters are allowed by symmetry in the Landau–Ginzburg free energy. Here, from renormalization group analysis, we show that second-order quantum phase transitions can occur at such putatively first-order transitions in interacting two-dimensional Dirac semimetals. As such type of Landau-forbidden quantum critical points are induced by gapless fermions, we call them fermion-induced quantum critical points. We further introduce a microscopic model of SU(N) fermions on the honeycomb lattice featuring a transition between Dirac semimetals and Kekule valence bond solids. Remarkably, our large-scale sign-problem-free Majorana quantum Monte Carlo simulations show convincing evidences of a fermion-induced quantum critical points for N = 2, 3, 4, 5 and 6, consistent with the renormalization group analysis. We finally discuss possible experimental realizations of the fermion-induced quantum critical points in graphene and graphene-like materials., Quantum phase transitions are governed by Landau-Ginzburg theory and the exceptions are rare. Here, Li et al. propose a type of Landau-forbidden quantum critical points induced by gapless fermions in two-dimensional Dirac semimetals.

Two-sided assembly lines are widely applied in plants for producing large-sized high volume products, such as trucks and buses. Since the two-sided assembly line balancing problem (TALBP) is NP-hard, it is difficult to get an optimal solution in polynomial time. Therefore, a novel swarm based heuristic algorithm named gravitational search algorithm (GSA) is proposed to solve this problem with the objective of minimizing the number of mated-stations and the number of stations simultaneously. In order to apply GSA to solving the TALBP, an encoding scheme based on the random-keys method is used to convert the continuous positions of the GSA into the discrete task sequence. In addition, a new decoding scheme is implemented to decrease the idle time related to sequence-dependent finish time of tasks. The corresponding experiment results demonstrate that the proposed algorithm outperforms other well-known algorithms.

Situated reconstitution is proposed in this paper to cope with un-manifold polyhedral from the function to form mapping processes. Specifically the situated reconstitution is not simply re-arrangement of geometric elements, mainly face entities in the un-manifold polyhedral, rather it needs a complex geometric/algebraic reasoning to reconstitute a manifold object, novel mathematical as well as AI techniques are introduced in this paper, several tools are developed to testify the proposed situated reconstitution in the “top-down” design automation systems.

This thesis proposes a multi-project management method based on Gantt chart and network planning techniques in modern corporate multi-project management by analysing characteristics and status quo of corporate multi-project management and basing on features of multi-project management and Gantt chart and network planning techniques.

A fundamental open issue in physics is whether and how the fermion sign problem in quantum Monte Carlo (QMC) simulations can be solved generically. Here, we show that Majorana-time-reversal (MTR) symmetries can provide a unifying principle to solve the fermion sign problem in interacting fermionic models. By systematically classifying Majorana-bilinear operators according to the anti-commuting MTR symmetries they respect, we rigorously proved that there are two and only two fundamental symmetry classes which are sign-problem-free and which we call the "Majorana class" and "Kramers class", respectively. Novel sign-problem-free models in the Majorana class include interacting topological superconductors and interacting models of charge-4e superconductors. We believe that our MTR unifying principle could shed new light on sign-problem-free QMC simulation on strongly correlated systems and interacting topological matters., Accepted by Phys. Rev. Lett. Added more references and moved part of the paper into the Supplemental Material

We study the magnetic response of superconducting $\gamma$-Ga via low temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex cores rely substantially on the Ga geometry, and exhibit an unexpectedly-large axial elongation with aspect ratio up to 40 in rectangular Ga nano-strips (width $l$ $, Comment: published in Phys. Rev. B as a Rapid Communication

Many features of charge-4e superconductors remain unknown because even the "mean-field Hamiltonian" describing them is an interacting model. Here we introduce an interacting model to describe a charge-4e superconductor (SC) deep in the superconducting phase, and explore its properties using quantum Monte Carlo (QMC) simulations. The QMC is sign-problem-free, but only when a Majorana representation is employed. As a function of the chemical potential we observe two sharply-distinct behaviors: a "strong" quarteting phase in which charge-4e quartets are tightly bound (like molecules) so that charge-2e pairing does not occur even in the temperature $T \to 0$ limit, and a "weak" quarteting phase in which a further transition to a charge-2e superconducting phase occurs at a lower critical temperature. Analogous issues arise in a putative Z4 spin-liquid with a pseudo-Fermi surface and in characterizing charge-2e SCs with "odd frequency pairing" (or equivalently with a "composite order parameter") and metallic spin-nematics. Under certain circumstances, we also identified a stable T=0 charge-4e SC phase with gapless nodal quasiparticles. We further discuss possible relevance of our results to various experimental observations in 1/8-doped LBCO., Comment: 5 pages, 3 figures

Much attention has been devoted recently to identify possible ways to overcome the notorious sign problem encountered in quantum Monte Carlo simulations. The authors of this paper propose a new method based on Majorana representation of complex fermions, which they dub Majorana Quantum Monte Carlo (MQMC). They find a class of SU(N) fermionic models which are sign-free in MQMC but cannot be solved with other available methods.