다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Weyl and Dirac semimetals are three-dimensional phases of matter with gapless electronic excitations that are protected by topology and symmetry. As three-dimensional analogs of graphene, they have generated much recent interest. Deep connections exist with particle physics models of relativistic chiral fermions, and, despite their gaplessness, to solid-state topological and Chern insulators. Their characteristic electronic properties lead to protected surface states and novel responses to applied electric and magnetic fields. The theoretical foundations of these phases, their proposed realizations in solid-state systems, and recent experiments on candidate materials as well as their relation to other states of matter are reviewed.

Weyl and Dirac semimetals in three-dimensional solids

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Nanoporous 12CaO$\cdot$Al$_2$O$_3$ (C12A7:e$^-$), known as a famous electride and electron source material, was recently proposed to boost catalytic activity in C12A7:e$^-$ based catalysts. However, the fundamental mechanism on such catalytic enhancement keeps in debate currently. Here, by means of symmetry analysis and first-principles calculations, we discover that this famous electride material, surprisingly, hosts interstitial-electrons composed multiple-fold fermions that helps to understand the catalytic nature of C12A7:e$^-$ based catalysts. The multiple-fold fermions contain a sixfold- and a fourfold- degenerate point, locating at high symmetric points near the Fermi energy. Remarkably, comparing with traditional Weyl/Dirac fermions, the multiple-fold fermions are found to show extremely longer Fermi arcs on the C12A7:e$^-$ (001) surface. As the result, this surface is highly active and carries a relatively low Gibbs free energy ($\Delta \rm G_{H^*} = 0.24$ eV) during the catalytic process. This G is also much lower than typical Weyl/Dirac catalysts proposed previously. This work offers a guiding principle for understanding catalytic nature of electrides and topological quantum catalysts as well.

Interstitial-Electrons Composed Multiple-Fold Fermions and Insights on Catalytic Nature in Nanoporous Electride C12A7:e$^-$

Xiangyu Luo1,3,†, Hao Chen1,3,†, Yinghao Li1,3,†, Qiang Gao, Chaohui Yin, Hongtao Yan, Taimin Miao, Hailan Luo, Yingjie Shu, Yiwen Chen, Chengtian Lin, Shenjin Zhang, Zhimin Wang, Fengfeng Zhang, Feng Yang, Qinjun Peng, Guodong Liu, Lin Zhao, Zuyan Xu, Tao Xiang and X. J. Zhou1,3,6,7,∗ National Lab for Superconductivity, Beijing National laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China Beijing National laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China University of Chinese Academy of Sciences, Beijing 100049, China Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China Beijing Academy of Quantum Information Sciences, Beijing 100193, China †These authors contributed equally to this work. ∗Corresponding author: XJZhou@iphy.ac.cn

Electronic Origin of High-Tc Maximization and Persistence in Trilayer Cuprate Superconductors

The metastable spin gapless semiconductor Ti2MnAl results from the kinetic arrest of atomic diffusion during sample preparation from the high-temperature relatively low-symmetric phase to the low-temperature high-symmetric phase.

Kinetic arrest of atomic diffusion-induced spin gapless semiconductor in Ti2MnAl Heusler compound

The most fundamental symmetry in condensed matter physics is the crystallographic symmetry, such that solids could exhibit unconventional excitations beyond Dirac and Weyl fermions. Among the unconventional fermions, the sextuple excitation has been predicted in many nonmagnetic materials. However, the study of magnetic sextuple excitations has fallen behind because of the complicated magnetic structures of materials. Here we perform a systematic search for ferromagnetic (FM) sextuple points (SPs) in the absence of spin-orbit coupling. Based on 230 space groups (SGs), we find there are 5 SGs that could host SPs at high-symmetry points. Regarding the stability of the sextuple excitation, we reveal that the minimum little point group at where the SP locates is ${\mathrm{T}}_{d}$. To support this result, we construct the effective model based on the $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ method, from which the linear dispersion can be read off. Via first-principles calculations, we also identify 67 FM material candidates, which realize the SPs with completely/incompletely spin polarized. To support our theory, we pick one of the FM materials, ${\mathrm{Rb}}_{4}{\mathrm{O}}_{6}$, as an example in which there is a fully spin-polarized SP. Finally, our work paves the way to study the spin-polarized SPs and provides a platform to realize the spintronic associated with sextuple excitations. 

Guodong Liu

Papers

Interstitial-Electrons Composed Multiple-Fold Fermions and Insights on Catalytic Nature in Nanoporous Electride C12A7:e$^-$

Electronic Origin of High-Tc Maximization and Persistence in Trilayer Cuprate Superconductors

Kinetic arrest of atomic diffusion-induced spin gapless semiconductor in Ti2MnAl Heusler compound

Spin-polarized sextuple excitations in ferromagnetic materials

Inorganic Semiconductor Nanoarrays as Photoanodes for Solar Cells