Shudan's homepage

2021

• Vladyslav Kozii, Alexander Avdoshkin, Shudan Zhong, and Joel E Moore. Intrinsic anomalous hall conductivity in non-uniform electric field. Phys. Rev. Lett., 126:156602, Apr 2021. arXiv:2010.07322, doi:10.1103/PhysRevLett.126.156602.
  [abstract▼] [details] [full text] [BibTeX▼]

  We study how the intrinsic anomalous Hall conductivity is modified in two-dimensional crystals with broken time-reversal symmetry due to weak inhomogeneity of the applied electric field. Focusing on a clean non-interacting two-band system without band crossings, we derive the general expression for the Hall conductivity at small finite wavevector \(q\) to order \(q^2\) , which governs the Hall response to the second gradient of the electric field. Using the Kubo formula, we show that the answer can be expressed through the Berry curvature, Fubini-Study quantum metric, and the rank-3 symmetric tensor which is related to the quantum geometric connection and physically corresponds to the gauge-invariant part of the third cumulant of the position operator. We further compare our results with the predictions made within the semiclassical approach. By deriving the semiclassical equations of motion, we reproduce the result obtained from the Kubo formula in some limits. We also find, however, that the naïve semiclassical description in terms of the definite position and momentum of the electron is not fully consistent because of singular terms originating from the Heisenberg uncertainty principle.

  @article{kozii2021,
      author = "Kozii, Vladyslav and Avdoshkin, Alexander and Zhong, Shudan and Moore, Joel E",
      title = "Intrinsic anomalous Hall conductivity in non-uniform electric field",
      journal = "Phys. Rev. Lett.",
      volume = "126",
      issue = "15",
      pages = "156602",
      numpages = "6",
      year = "2021",
      month = "Apr",
      publisher = "American Physical Society",
      doi = "10.1103/PhysRevLett.126.156602",
      eprint = "2010.07322"
  }
  

2020

• Kexuan Sun, Shudan Zhong, and Hong Xu. Learning embeddings of directed networks with text-associated nodes—with application in software package dependency networks. In Proceedings of the 2020 BigGraphs Workshop at IEEE BigData. 2020.
  [abstract▼] [details] [full text] [data] [code] [BibTeX▼]

  A network embedding consists of a vector representation for each node in the network. Network embeddings have shown their usefulness in node classification and visualization in many real-world application domains, such as social networks and web networks. While directed networks with text associated with each node, such as citation networks and software package dependency networks, are commonplace, to the best of our knowledge, their embeddings have not been specifically studied. In this paper, we create PCTADW-1 and PCTADW-2, two algorithms based on NNs that learn embeddings of directed networks with text associated with each node. We create two new labeled directed networks with text- associated node: The package dependency networks in two popular GNU/Linux distributions, Debian and Fedora. We experimentally demonstrate that the embeddings produced by our NNs resulted in node classification with better quality than those of various baselines on these two networks. We observe that there exist systematic presence of analogies (similar to those in word embeddings) in the network embeddings of software package dependency networks. To the best of our knowledge, this is the first time that such a systematic presence of analogies is observed in network and document embeddings. This may potentially open up a new venue for better understanding networks and documents algorithmically using their embeddings as well as for better human understanding of network and document embeddings.

  @inproceedings{sun2020,
      author = "Sun, Kexuan and Zhong, Shudan and Xu, Hong",
      title = "Learning Embeddings of Directed Networks with Text-Associated Nodes---with Application in Software Package Dependency Networks",
      booktitle = "Proceedings of the 2020 BigGraphs Workshop at IEEE BigData",
      year = "2020",
      customlinkdata = "https://doi.org/10.5281/zenodo.1410669",
      customlinkcode = "https://github.com/shudan/PCTADW"
  }
  

2019

• Shudan Zhong and Hong Xu. Intelligently recommending key bindings on physical keyboards with demonstrations in Emacs. In Proceedings of the 24th International Conference on Intelligent User Interfaces (IUI), 12–17. 2019. doi:10.1145/3301275.3302272.
  [abstract▼] [details] [full text] [slides] [BibTeX▼]

  Physical keyboards have been peripheral input devices to electronic computers since early 1970s and become ubiquitous during the past few decades, especially in professional areas such as software programming, professional game playing, and document processing. In these real-world applications, key bindings, a fundamental vehicle for human to interact with software systems using physical keyboards, play a critical role in users' productivity. However, as essential applications of artificial intelligence research, research on intelligent user interfaces and recommender systems barely relates to key bindings on physical keyboards. In this paper, we develop a recommender system (referred to as EKBRS) for intelligently recommending key bindings with demonstration in Emacs, which we use as a base user interface. This is a brand new direction of intelligent user interface research and also a novel application of recommender systems. To the best of our knowledge, this is the world's first intelligent user interface that heavily exploits key bindings of physical keyboards and the world's first recommender system for recommending key bindings. We empirically show the effectiveness of our recommender system and briefly discuss the applicability of this recommender system to other software systems.

  @inproceedings{zhong2019a,
      author = "Zhong, Shudan and Xu, Hong",
      title = "Intelligently Recommending Key Bindings on Physical Keyboards with Demonstrations in {Emacs}",
      year = "2019",
      booktitle = "Proceedings of the 24th International Conference on Intelligent User Interfaces (IUI)",
      pages = "12--17",
      doi = "10.1145/3301275.3302272",
      customlinkslides = "http://files.hong.me/papers/zhong2019a-slides.pdf"
  }
  

2016

• Takahiro Morimoto, Shudan Zhong, Joseph Orenstein, and Joel E. Moore. Semiclassical theory of nonlinear magneto-optical responses with applications to topological Dirac/Weyl semimetals. Physical Review B, 94:245121, 2016. arXiv:1609.05932, doi:10.1103/PhysRevB.94.245121.
  [abstract▼] [details] [full text] [BibTeX▼]

  We study nonlinear magneto-optical responses of metals by a semiclassical Boltzmann equation approach. We derive general formulas for linear and second order nonlinear optical effects in the presence of magnetic fields that include both Berry curvature and orbital magnetic moment. Applied to Weyl fermions, the semiclassical approach (i) captures the directional anisotropy of linear conductivity under magnetic field as a consequence of an anisotropic \(B^2\) contribution, which may explain the low-field regime of recent experiments; (ii) predicts strong second harmonic generation proportional to \(B\) that is enhanced as the Fermi energy approaches the Weyl point, leading to large nonlinear Kerr rotation. Moreover, we show that the semiclassical formula for the circular photogalvanic effect arising from the Berry curvature dipole is reproduced by a full quantum calculation in the case of two bands using a Floquet approach.

  @article{morimoto2016,
      author = "Morimoto, Takahiro and Zhong, Shudan and Orenstein, Joseph and Moore, Joel E.",
      title = "Semiclassical theory of nonlinear magneto-optical responses with applications to topological {Dirac/Weyl} semimetals",
      journal = "Physical Review B",
      volume = "94",
      issue = "24",
      pages = "245121",
      numpages = "15",
      year = "2016",
      publisher = "American Physical Society",
      doi = "10.1103/PhysRevB.94.245121",
      eprint = "1609.05932"
  }
  

• Shudan Zhong, Joel E. Moore, and Ivo Souza. Gyrotropic magnetic effect and the orbital moment on the Fermi surface. Physical Review Letter, 116:077201, 2016. arXiv:1510.02167, doi:10.1103/PhysRevLett.116.077201.
  [abstract▼] [details] [full text] [BibTeX▼]

  The current density \(\textbf J^\textbf B\) induced in a clean metal by a magnetic field \(\textbf B\) is formulated as the low-frequency limit of natural optical activity, or natural gyrotropy. Working with a multiband Pauli Hamiltonian, we obtain from the Kubo formula a simple expression for \(\alpha^\textgme_ij=j^\textbf B_i/B_j\) in terms of the intrinsic magnetic moment (orbital plus spin) of the Bloch electrons on the Fermi surface. An alternate semiclassical derivation provides an intuitive picture of the effect, and takes into account the influence of scattering processes in dirty metals. This ``gyrotropic magnetic effect'' is fundamentally different from the chiral magnetic effect driven by the chiral anomaly and governed by the Berry curvature on the Fermi surface, and the two effects are compared for a minimal model of a Weyl semimetal. Like the Berry curvature, the intrinsic magnetic moment should be regarded as a basic ingredient in the Fermi-liquid description of transport in broken-symmetry metals.

  @article{zhong2016,
      author = "Zhong, Shudan and Moore, Joel E. and Souza, Ivo",
      title = "Gyrotropic magnetic effect and the orbital moment on the {Fermi} surface",
      journal = "Physical Review Letter",
      volume = "116",
      issue = "7",
      pages = "077201",
      numpages = "6",
      year = "2016",
      publisher = "American Physical Society",
      doi = "10.1103/PhysRevLett.116.077201",
      eprint = "1510.02167"
  }
  

2015

• Shudan Zhong, Joseph Orenstein, and Joel E. Moore. Optical gyrotropy from axion electrodynamics in momentum space. Physical Review Letter, 115:117403, 2015. arXiv:1503.02715, doi:10.1103/PhysRevLett.115.117403.
  [abstract▼] [details] [full text] [BibTeX▼]

  Several emergent phenomena and phases in solids arise from configurations of the electronic Berry phase in momentum space that are similar to gauge field configurations in real space such as magnetic monopoles. We show that the momentum-space analogue of the ``axion electrodynamics'' term \(\textbf E\cdot \textbf B\) plays a fundamental role in a unified theory of Berry-phase contributions to optical gyrotropy in time-reversal invariant materials and the chiral magnetic effect. The Berry-phase mechanism predicts that the rotatory power along the optic axes of a crystal must sum to zero, a constraint beyond that stipulated by point-group symmetry, but observed to high accuracy in classic experimental observations on alpha quartz. Furthermore, the Berry mechanism provides a microscopic basis for the surface conductance at the interface between gyrotropic and nongyrotropic media.

  @article{zhong2015,
      author = "Zhong, Shudan and Orenstein, Joseph and Moore, Joel E.",
      title = "Optical Gyrotropy from Axion Electrodynamics in Momentum Space",
      journal = "Physical Review Letter",
      volume = "115",
      issue = "11",
      pages = "117403",
      numpages = "5",
      year = "2015",
      publisher = "American Physical Society",
      doi = "10.1103/PhysRevLett.115.117403",
      eprint = "1503.02715"
  }
  

2013

• Mikhail Kostylev, Shudan Zhong, Junjia Ding, and Adekunle O. Adeyeye. Resonance properties of bi-component arrays of magnetic dots magnetized perpendicular to their planes. Journal of Applied Physics, 114(11):113910, 2013. doi:10.1063/1.4821771.
  [abstract▼] [details] [BibTeX▼]

  The spin wave spectrum of dense arrays of rectangular elements periodically arranged in a two-dimensional magnonic crystal with a complex unit cell and magnetized perpendicularly to the array plane has been characterized using broadband ferromagnetic resonance (FMR) spectroscopy. The crystal's unit cell consists of non-collinear orientations of constituting elongated rectangular elements. We found that only one mode is excited in the perpendicular-to-plane FMR in complete magnetic saturation. We also conducted out-of-plane angle resolved measurements of the FMR resonance field. We observe splitting of the singlet observed for the perfect perpendicular-to-plane orientation of the applied field into a doublet upon a tilt of the field from this orientation. The splitting of the singlet into a doublet is explained as an experimental evidence of dipole coupling of the elements on the arrays. Our experimental observations are in good agreement with the theory we developed to describe the magnetization dynamics on this periodic array.

  @article{kostylev2013,
      author = "Kostylev, Mikhail and Zhong, Shudan and Ding, Junjia and Adeyeye, Adekunle O.",
      doi = "10.1063/1.4821771",
      year = "2013",
      publisher = "{AIP} Publishing",
      volume = "114",
      number = "11",
      pages = "113910",
      title = "Resonance properties of bi-component arrays of magnetic dots magnetized perpendicular to their planes",
      journal = "Journal of Applied Physics"
  }