arXiv subjects

Xuejiao Chen

Publications and source records attributed to Xuejiao Chen.

16 recordsLinked to original sources

arXiv2026

Temperature-driven structural phase transitions in SmNiO$_3$: insights from deep potential molecular dynamics simulations

The metal-insulator transition (MIT) in rare-earth nickelates exemplifies the intricate coupling between lattice dynamics and electronic effects. This strong interplay makes it challenging to disentangle their individual roles in driving the transition in RNiO3. Here, we isolate the structure response from electronic effect by employing molecular dynamics (MD) simulations based on a machine-learned interatomic potential. Taking SmNiO3 as a prototypical system, our simulations show that the structural phase transition is intrinsically temperature-driven and occurs spontaneously via collective lattice distortions. The simulated critical temperature is 340 K and can be further tuned by pressure. These findings provide atomistic insights into the understanding of structural evolution in triggering the phase transition and hence the MIT in RNiO3.

cond-mat.mtrl-sci↗

arXiv2025

Emergent Chiral Spin Crystal Phase in (111) SrRuO3 Thin Films

Perovskite ruthenates are fascinating playgrounds for exploring topological spin textures, but generally rely on extrinsic mechanisms to trigger the noncoplanar states. Here we report the discovery of an emergent chiral spin crystal phase in (111) SrRuO3 epitaxial films, characterized by a significant topological Hall effect and noncoplanar spin arrangements with different propagation vectors along two orthogonal directions. Instead of driven by the enhanced Dzyaloshinskii-Moriya interaction due to broken inversion symmetry at heterointerfaces, this emergent state arises intrinsically from the interplay of dipolar interactions and magnetic frustration, leading to the stabilization of topological phases in much thicker films. These findings open a new pathway for creating and controlling the topological spin states in perovskites, with broad implications for spintronic device design.

cond-mat.str-el↗

arXiv2025

From Ferromagnet to Antiferromagnet: Dimensional Crossover in (111) SrRuO3 Ultrathin Films

SrRuO3 is a canonical itinerant ferromagnet, yet its properties in the extreme two-dimensional limit on a (111) crystal plane remain largely unexplored. Here, we demonstrate a complete transformation of its ground state driven by dimensional reduction. As the thickness of (111)-oriented SrRuO3 films is reduced to a few unit cells, the system transitions from a metallic ferromagnet to a semiconducting antiferromagnet. This emergent antiferromagnetism is evidenced by a vanishing magnetic remanence and most strikingly, by the appearance of an unconventional twelve-fold anisotropic magnetoresistance. First-principles calculations confirm that an A-type antiferromagnetic order is the stable ground state in the ultrathin limit. Our findings establish (111) dimensional engineering as a powerful route to manipulate correlated electron states and uncover novel functionalities for antiferromagnetic spintronics.

cond-mat.str-el↗

arXiv2025

Intrinsic Strain-Driven Topological Evolution in SrRuO3 via Flexural Strain Engineering

Strain engineering offers a powerful route to tailor topological electronic structures in correlated oxides, yet conventional epitaxial strain approaches introduce extrinsic factors such as substrate-induced phase transitions and crystalline quality variations, which makes the unambiguous identification of the intrinsic strain effects challenging. Here, we develop a flexural strain platform based on van der Waals epitaxy and flexible micro-fabrication, enabling precise isolation and quantification of intrinsic strain effects on topological electronic structures in correlated oxides without extrinsic interference. Through strain-dependent transport measurements of the Weyl semimetal SrRuO3, we observed a significant enhancement of anomalous Hall conductivity by 21% under a tiny strain level of 0.2%, while longitudinal resistivity remains almost constant -- a hallmark of intrinsic topological response. First-principles calculations reveal a distinct mechanism where strain-driven non-monotonic evolution of Weyl nodes across the Fermi level, exclusively governed by lattice constant modulation, drives the striking AHC behavior. Our work not only highlights the pivotal role of pure lattice strain in topological regulation but also establishes a universal platform for designing flexible topological oxide devices with tailored functionalities.

cond-mat.mtrl-sci↗

arXiv2024

Giant domain wall anomalous Hall effect in an antiferromagnet

Generally, the dissipationless Hall effect in solids requires time-reversal symmetry breaking (TRSB), where TRSB induced by external magnetic field results in ordinary Hall effect, while TRSB caused by spontaneous magnetization gives rise to anomalous Hall effect (AHE) which scales with the net magnetization. The AHE is therefore not expected in antiferromagnets with vanishing small magnetization. However, large AHE was recently observed in certain antiferromagnets with noncolinear spin structure and nonvanishing Berry curvature. Here, we report another origin of AHE in a layered antiferromagnet EuAl2Si2, namely the domain wall (DW) skew scattering with Weyl points near the Fermi level, in experiments for the first time. Interestingly, the DWs form a unique periodic stripe structure with controllable periodicity by external magnetic field, which decreases nearly monotonically from 975 nm at 0 T to 232 nm at 4 T. Electrons incident on DW with topological bound states experience strong asymmetric scattering, leading to a giant AHE, with the DW Hall conductivity (DWHC) at 2 K and 1.2 T reaching a record value of ~ 1,5100 S cm-1 among bulk systems and being two orders of magnitude larger than the intrinsic anomalous Hall conductivity. The observation not only sets a new paradigm for exploration of large anomalous Hall effect, but also provides potential applications in spintronic devices.

cond-mat.str-el↗

arXiv2024

Charge and spin instabilities in superconducting La$_3$Ni$_2$O$_7$

Motivated by the recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ under high pressure, we explore its potential charge and spin instabilities through combined model analysis and first-principles calculations. Taking into account the small charge-transfer nature of high valence nickel, a fully correlated two-cluster model identifies a lattice-coupled charge instability characterized by substantial short-range fluctuations of oxygen holes. This instability is corroborated by density-functional-theory plus $U$ calculations that also reveal a strong tendency towards concurrent antiferromagnetic ordering. The charge, spin, and associated lattice instabilities are significantly suppressed with increasing external pressure, contributing to the emergence of superconductivity in pressurized La$_3$Ni$_2$O$_7$. Carrier doping is found to effectively suppress these instabilities, suggesting a viable strategy to stabilize a superconducting phase under ambient pressure.

cond-mat.supr-con↗

arXiv2024

Noncentrosymmetric Nowotny Chimney Ladder Ferromagnet Cr4Ge7 with a High Curie Temperature of ~ 207 K

Noncentrosymmetric magnets usually host intriguing magnetic interactions inherent the crystal structure with broken inversion symmetry, which can give rise to rich magnetic behaviors. We report herein the high-pressure synthesis, crystal structure, magnetizations and magnetic structure of a so-called Nowotny chimney ladder compound Cr4Ge7. Our analysis on the powder neutron diffraction data revises the crystal structure as a noncentrosymmetric space group (P-4c2, No.116). It exhibits two magnetic orders within the temperature range of 2 - 400 K. The first order at ~ 207 K associated with a small magnetic moment of ~ 0.75 miuB is assigned to a commensurate ferromagnetic structure with a propagation vector k = (0, 0, 0). The weak itinerant ferromagnet nature should be caused by the complex Cr spin orders from different Wyckoff positions. The second order at ~ 18 K is assumed to arise from a competition between the Dzyaloshinskii-Moria and Heisenberg interactions. The results provide an excellent platform for study on intricate interactions between various magnetic exchanges as well as for the exploration of high temperature exotic magnetic properties which host potential applications in next-generation spintronics.

cond-mat.str-el↗

arXiv2023

Pressure-induced one-dimensional oxygen ion diffusion channel in lead-apatite

Recently, Lee et al. claimed that the experimental observation of room-temperature ambient-pressure superconductivity in a Cu-doped lead-apatite (Pb10-xCux(PO4)6O). The study revealed the Cu doping induces a chemical pressure, resulting in a structural contraction of one-dimensional Cu-O-Cu atomic column. This unique structure promotes a one-dimensional electronic conduction channel along the c-axis mediated by the O atoms, which may be related to superconductivity. These O atoms occupy 1/4 of the equivalent positions along the c-axis and exhibit a low diffusion activation energy of 0.8 eV, indicating the possibility of diffusion between these equivalent positions. Here, using machine-learning based deep potential, we predict the pressure-induced fast diffusion of 1/4-occupied O atoms along the one-dimensional channel in Pb10(PO4)6O at 500 K, while the frameworks of Pb triangles and PO4 tetrahedrons remain stable. The calculation results also indicate Cu doping can provide appropriate effective chemical pressure, indicating the one-dimensional ion diffusion channel may appear in Pb9Cu(PO4)6O, even at ambient pressure. Our finding shows that the one-dimensional ions diffusion channel may be an important factor to affects the fabrication and electrical measurement of doped lead-apatite.

cond-mat.mtrl-sci↗

arXiv2023

Magnetism and berry phase manipulation in an emergent structure of perovskite ruthenate by (111) strain engineering

The interplay among symmetry of lattices, electronic correlations, and Berry phase of the Bloch states in solids has led to fascinating quantum phases of matter. A prototypical system is the magnetic Weyl candidate SrRuO3, where designing and creating electronic and topological properties on artificial lattice geometry is highly demanded yet remains elusive. Here, we establish an emergent trigonal structure of SrRuO3 by means of heteroepitaxial strain engineering along the [111] crystallographic axis. Distinctive from bulk, the trigonal SrRuO3 exhibits a peculiar XY-type ferromagnetic ground state, with the coexistence of high-mobility holes likely from linear Weyl bands and low-mobility electrons from normal quadratic bands as carriers. The presence of Weyl nodes are further corroborated by capturing intrinsic anomalous Hall effect, acting as momentum-space sources of Berry curvatures. The experimental observations are consistent with our first-principles calculations, shedding light on the detailed band topology of trigonal SrRuO3 with multiple pairs of Weyl nodes near the Fermi level. Our findings signify the essence of magnetism and Berry phase manipulation via lattice design and pave the way towards unveiling nontrivial correlated topological phenomena.

cond-mat.str-el↗

arXiv2023

Magnetic tuning of band topology evidenced by exotic quantum oscillations in the Dirac semimetal EuMnSb$_2$

Interplay between magnetism and electronic band topology is of central current interest in topological matter research. We use quantum oscillations as powerful tool to probe the evolution of band topology in the Dirac semimetal EuMnSb$_2$. The Eu local 4f magnetic moments display different antiferromagnetic states below 25 K and a field-polarized phase above 16 T. Upon cooling from 65 K into the field-polarized state, an exotic temperature dependent shift of oscillation peaks arises, accompanied by the development of non-zero Berry phase and a huge unconventional splitting of the oscillations. Band-structure calculations confirm the change from trivial to non-trivial band topology induced by the ferromagnetic Eu state, classifying EuMnSb$_2$ as unique magnetic topological semimetal.

cond-mat.str-el↗

arXiv2022

Pressure-induced ideal Weyl semimetal state in the layered antiferromagnet EuCd2As2

The rich nontrivial topological phases rooted in the interplay between magnetism and topology in the layered antiferromagnet EuCd2As2 have captured vast attention, especially the ideal Weyl semimetal state realized in the spin-polarized ferromagnetic (FM) structure driven by a moderate external magnetic field. In this work, combining high-pressure magnetotransport measurements, structure chracterizations and first principles calculations, we find that application of pressure can also realize the ideal Weyl state in EuCd2As2 through driving the in-plane antiferromagnetic state across an intermediate in-plane FM state then into the out-of-plane FM state. Our high-pressure angle dispersive X-ray diffraction and X-ray absorption near-edge spectroscopy measurements excluded structure transition and/or change of Eu2+ valence state as the sources for the magnetic phase transitions. Alternatively, the apparently reduced axial ratio (c/a) and compressed Eu-layer space distance should play important roles. Our result provides an alternative way to realize the ideal Weyl semimetal state in EuCd2As2 and would be instructive for the exploration of exotic topological properties in such layered magnetic topological phase with strongly competing magnetic exchanges by using high pressure.

cond-mat.mtrl-sci↗

arXiv2021

ByteSGAN: A Semi-supervised Generative Adversarial Network for Encrypted Traffic Classification of SDN Edge Gateway in Green Communication Network

With the rapid development of Green Communication Network, the types and quantity of network traffic data are accordingly increasing. Network traffic classification become a non-trivial research task in the area of network management and security, which not only help to improve the fine-grained network resource allocation, but also enable policy-driven network management. Meanwhile, the combination of SDN and Edge Computing can leverage both SDN at its global visiability of network-wide and Edge Computing at its low latency and good privacy-preserving. However, capturing large labeled datasets is a cumbersome and time-consuming manual labor. Semi-Supervised learning is an appropriate technique to overcome this problem. With that in mind, we proposed a Generative Adversarial Network (GAN)-based Semi-Supervised Learning Encrypted Traffic Classification method called \emph{ByteSGAN} embedded in SDN Edge Gateway to achieve the goal of traffic classification in a fine-grained manner to further improve network resource utilization. ByteSGAN can only use a small number of labeled traffic samples and a large number of unlabeled samples to achieve a good performance of traffic classification by modifying the structure and loss function of the regular GAN discriminator network in a semi-supervised learning way. Based on public dataset 'ISCX2012 VPN-nonVPN', two experimental results show that the ByteSGAN can efficiently improve the performance of traffic classifier and outperform the other supervised learning method like CNN.

cs.CR↗

arXiv2018

A Hierarchical Approach to Encrypted Data Packet Classification in Smart Home Gateways

With the pervasive network based services in smart homes, traditional network management cannot guarantee end-user quality-of-experience (QoE) for all applications. End-user QoE must be supported by efficient network quality-of-service (QoS) measurement and efficient network resource allocation. With the software-defined network technology, the core network may be controlled more efficiently by a network service provider. However, end-to-end network QoS can hardly be improved the managing the core network only. In this paper, we propose an encrypted packet classification scheme for smart home gateways to improve end-to-end QoS measurement from the network operator side. Furthermore, other services such as statistical data collecting, billing to service providers, etc., can be provided without compromising end-user privacy nor security of a network. The proposed encrypted packet classification scheme has a two-level hierarchical structure. One is the service level, which is based on applications that have the same network QoS requirements. A faster classification scheme based on deep learning is proposed to achieve real-time classification with high accuracy. The other one is the application level, which is based on fine-grained applications. A non-real-time classifier can be applied to provide high accuracy. Evaluation is conducted on both level classifiers to demonstrate the efficiency and accuracy of the two types of classifiers.

cs.CR↗

arXiv2018

Co Hijacking Monitor: Collaborative Detecting and Locating Mechanism for HTTP Spectral Hijacking

With the rapid growth of mobile internet, mobile application, like website navigation, searching, e-Shopping and app download, etc. are all popular in worldwide. Meanwhile, it become more and more popular that traditional HTTP protocol, which is also applying in not only web browsing but also communication between mobile application clients and servers. Besides, it has made HTTP Hijacking profitable. Furthermore, it has brought a lot of troubles for users, network operators and ISP. We analyze the principle of HTTP spectral Hijacking and present a mechanism of collaboratively detecting and locating called Co HijackingMonitor. Experimental result shows that, Co HijackingMonitor can solve the hijacking problem effectively.

cs.CR↗

arXiv2018

A Fog-based Architecture and Programming Model for IoT Applications in the Smart Grid

The smart grid utilizes many Internet of Things (IoT) applications to support its intelligent grid monitoring and control. The requirements of the IoT applications vary due to different tasks in the smart grid. In this paper, we propose a new computing paradigm to offer location-aware, latencysensitive monitoring and intelligent control for IoT applications in the smart grid. In particular, a new fog-based architecture and programming model is designed. Fog computing extends computing to the edge of a network, which has a perfect match to IoT applications. However, existing schemes can hardly satisfy the distributed coordination within fog computing nodes in the smart grid. In the proposed model, we introduce a new distributed fog computing coordinator, which periodically gathers information of fog computing nodes, e.g., remaining resources, tasks, etc. Moreover, the fog computing coordinator also manages jobs so that all computing nodes can collaborate on complex tasks. In addition, we construct a working prototype of intelligent electric vehicle service to evaluate the proposed model. Experiment results are also presented to demonstrate that our proposed model exceed the traditional fog computing schemes for IoT applications in the smart grid.

cs.NI↗

arXiv2018

A Smart Home Gateway Platform for Data Collection and Awareness

Smart homes have attracted much attention due to the expanding of Internet-of-Things (IoT) and smart devices. In this paper, we propose a smart gateway platform for data collection and awareness in smart home networks. A smart gateway will replace the traditional network gateway to connect the home network and the Internet. A smart home network supports different types of smart devices, such as in home IoT devices, smart phones, smart electric appliances, etc. A traditional network gateway is not capable of providing quality-of-service measurement, user behavioral analytics, or network optimization. Such tasks are traditionally performed with measurement agents such as optical splitters or network probes deployed in the core network. Our proposed platform is a lightweight plug-in for the smart gateway to accomplish data collection, awareness and reporting. While the smart gateway is able to adjust the control policy for data collection and awareness locally, a cloud-based controller is also included for more refined control policy updates. Furthermore, we propose a multi-dimensional awareness framework to achieve accurate data awareness at the smart gateway. The efficiency of data collection and accuracy of data awareness of the proposed platform is demonstrated based on the tests using actual data traffic from a large number of smart home users.

cs.NI↗