Frontiers of Physics

ISSN 2095-0462

ISSN 2095-0470(Online)

CN 11-5994/O4

2017 Impact Factor: 1.892



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Numerical investigation of relationship between water contact angle and drag reduction ratio of superhydrophobic surfaces
Liang Yin,Hai-Feng Zhang,Shu-Yuan Shi,Yao Lu,Yang Wang,Xiao-Wei Liu
Frontiers of Physics    2016, 11 (3): 114701-.
摘要   PDF (419KB)

This paper proposes a novel bubble model to analyze drag reduction. The relationship between the slip length and air bubble height is discussed. The numerical relationship between the surface contact angle and slip length is obtained using the solid-liquid contact ratio in the Cassie equation. The surface drag reduction ratio increases by 40% at low velocities when the solid liquid contact ratio decreases from 90% to 10%. An experimental setup to study liquid/solid friction drag is reported. The drag reduction ratio for the superhydrophobic surface tested experimentally is 30%–35% at low velocities. These results are similar to the simulation results obtained at low velocities.

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Recent advances in MXene: Preparation, properties, and applications
Lei Jin-Cheng(雷进程), Zhang Xu(张旭), Zhou Zhen(周震)
Frontiers of Physics    2015, 10 (3): 107303-null.
摘要   PDF (677KB)

Owing to the exceptional properties of graphene, intensive studies have been carried out on novel two-dimensional (2D) materials. In the past several years, an elegant exfoliation approach has been used to successfully create a new family of 2D transition metal carbides, nitrides, and carbonitrides, termed MXene, from layered MAX phases. More recently, some unique properties of MXene have been discovered leading to proposals of potential applications. In this review, we summarize the latest progress in development of MXene from both a theoretical and experimental view, with emphasis on the possible applications.

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Transport in graphene nanostructures
Christoph Stampfer, Stefan Fringes, Johannes Güttinger, Francoise Molitor, Christian Volk, Bernat Terrés, Jan Dauber, Stephan Engels, Stefan Schnez, Arnhild Jacobsen, Susanne Droscher, Thomas Ihn, Klaus Ensslin
Frontiers of Physics    2011, 6 (3): 271-293.
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Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quantum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching “paper-cutting” technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots. These quasi-one-dimensional (nanoribbons) and quasi-zero-dimensional (quantum dots) graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, we emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin–orbit coupling and weak hyperfine interaction in graphene.

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Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Dan-wei Zhang (张丹伟), Zi-dan Wang (汪子丹), Shi-liang Zhu (朱诗亮)
Frontiers of Physics    2012, 7 (1): 31-53.
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Quantum simulation is a powerful tool to study a variety of problems in physics, ranging from high-energy physics to condensed-matter physics. In this article, we review the recent theoretical and experimental progress in quantum simulation of Dirac equation with tunable parameters by using ultracold neutral atoms trapped in optical lattices or subject to light-induced synthetic gauge fields. The effective theories for the quasiparticles become relativistic under certain conditions in these systems, making them ideal platforms for studying the exotic relativistic effects. We focus on the realization of one, two, and three dimensional Dirac equations as well as the detection of some relativistic effects, including particularly the well-known Zitterbewegung effect and Klein tunneling. The realization of quantum anomalous Hall effects is also briefly discussed.

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The rise of two-dimensional MoS2 for catalysis
Jun Mao (毛军), Yong Wang (王勇), Zhilong Zheng (郑智龙), Dehui Deng (邓德会)
Frontiers of Physics    2018, 13 (4): 138118-.
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Two-dimensional (2D) MoS2 is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this article, we illustrate the active sites of 2D MoS2 and various strategies for enhancing its intrinsic catalytic activity. The recent advances in the use of 2D MoS2-based materials for applications such as thermocatalysis, electrocatalysis, and photocatalysis are discussed. We also discuss the future opportunities and challenges for 2D MoS2-based materials, in both fundamental research and industrial applications.

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Laser-induced breakdown spectroscopy in China
Zhe Wang, Ting-Bi Yuan, Zong-Yu Hou, Wei-Dong Zhou, Ji-Dong Lu, Hong-Bin Ding, Xiao-Yan Zeng
Frontiers of Physics    2014, 9 (4): 419-438.
摘要   PDF (325KB)

Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

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Quantum dynamics in ultracold atomic physics
Qiong-Yi He, Margaret D. Reid, Bogdan Opanchuk, Rodney Polkinghorne, Laura E. C. Rosales-Zárate, Peter D. Drummond
Frontiers of Physics    2012, 7 (1): 16-30.
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We review recent developments in the theory of quantum dynamics in ultracold atomic physics, including exact techniques and methods based on phase-space mappings that are applicable when the complexity becomes exponentially large. Phase-space representations include the truncated Wigner, positive-P and general Gaussian operator representations which can treat both bosons and fermions. These phase-space methods include both traditional approaches using a phase-space of classical dimension, and more recent methods that use a non-classical phase-space of increased dimensionality. Examples used include quantum Einstein–Podolsky–Rosen (EPR) entanglement of a four-mode BEC, time-reversal tests of dephasing in single-mode traps, BEC quantum collisions with up to 106 modes and 105 interacting particles, quantum interferometry in a multi-mode trap with nonlinear absorption, and the theory of quantum entropy in phase-space. We also treat the approach of variational optimization of the sampling error, giving an elementary example of a nonlinear oscillator.

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First-principle study on the optical response of phosphorene
Jia-He Lin, Hong Zhang, Xin-Lu Cheng
Frontiers of Physics    2015, 10 (4): 107301-null.
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The optical response of phosphorene nanostructures was studied using time-dependent density functional theory (TDDFT). Compared with the absorption spectrum of graphene, that of the phosphorene nanostructure exhibits high absorbance in the ultraviolet region, which indicates a high light absorptivity. In a low-energy resonance zone, a spectral band extends to the entire near-infrared regions. When the impulse excitation polarizes in the armchair-edge direction, the low-energy plasmon in a few-layer phosphorene nanostructure shows an apparent long-range charge-transfer excitation but is significantly less pronounced along the zigzag-edge direction. The edge configuration significantly affects the absorption spectrum of monolayer phosphorene nanostructures. The armchair-edge and the zigzag-edge serve different functions in the absorption spectrum. Moreover, the absorption spectrum of the few-layer phosphorene nanostructure changes with the number of layers when the impulse excitation polarizes in the armchair-edge direction. In addition, the change in the low-energy resonance zone is significantly different from that in the high-energy resonance zone.

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Topological nodal line semimetals predicted from first-principles calculations
Rui Yu,Zhong Fang,Xi Dai,Hongming Weng
Frontiers of Physics    2017, 12 (3): 127202-.
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Topological semimetals are newly discovered states of quantum matter, which have extended the concept of topological states from insulators to metals and attracted great research interest in recent years. In general, there are three kinds of topological semimetals, namely Dirac semimetals, Weyl semimetals, and nodal line semimetals. Nodal line semimetals can be considered as precursor states for other topological states. For example, starting from such nodal line states, the nodal line structure might evolve into Weyl points, convert into Dirac points, or become a topological insulator by introducing the spin–orbit coupling (SOC) or mass term. In this review paper, we introduce theoretical materials that show the nodal line semimetal state, including the all-carbon Mackay–Terrones crystal (MTC), anti-perovskite Cu3PdN, pressed black phosphorus, and the CaP3 family of materials, and we present the design principles for obtaining such novel states of matter.

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Two-dimensional materials: Emerging toolkit for construction of ultrathin high-efficiency microwave shield and absorber
Mingjun Hu, Naibo Zhang, Guangcun Shan, Jiefeng Gao, Jinzhang Liu, Robert K. Y. Li
Frontiers of Physics    2018, 13 (4): 138113-.
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Two-dimensional (2D) materials generally have unusual physical and chemical properties owing to the confined electro-strong interaction in a plane and can exhibit obvious anisotropy and a significant quantum-confinement effect, thus showing great promise in many fields. Some 2D materials, such as graphene and MXenes, have recently exhibited extraordinary electromagnetic-wave shielding and absorbing performance, which is attributed to their special electrical behavior, large specific surface area, and low mass density. Compared with traditional microwave attenuating materials, 2D materials have several obvious inherent advantages. First, similar to other nanomaterials, 2D materials have a very large specific surface area and can provide numerous interfaces for the enhanced interfacial polarization as well as the reflection and scattering of electromagnetic waves. Second, 2D materials have a particular 2D morphology with ultrasmall thickness, which is not only beneficial for the penetration and dissipation of electromagnetic waves through the 2D nanosheets, giving rise to multiple reflections and the dissipation of electromagnetic energy, but is also conducive to the design and fabrication of various well-defined structures, such as layer-by-layer assemblies, core–shell particles, and porous foam, for broadband attenuation of electromagnetic waves. Third, owing to their good processability, 2D materials can be integrated into various multifunctional composites for multimode attenuation of electromagnetic energy. In addition to behaving as microwave reflectors and absorbers, 2D materials can act as impedance regulators and provide structural support for good impedance matching and setup of the optimal structure. Numerous studies indicate that 2D materials are among the most promising microwave attenuation materials. In view of the rapid development and enormous advancement of 2D materials in shielding and absorbing electromagnetic wave, there is a strong need to summarize the recent research results in this field for presenting a comprehensive view and providing helpful suggestions for future development.

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Nanophotonics in China: Overviews and highlights
Zhi-Yuan Li
Frontiers of Physics    2012, 7 (6): 601-631.
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The major purpose of this paper is to present a brief overview of the history and the current status of nanophotonics research in China, and to highlight some research results in the past years made by the Chinese nanophotonics communities. I will first briefly introduce the principles of nanophotonics and several of its major disciplines including photonic crystals, plasmonics and metamaterials, and related artificial acoustic structures. Then I will highlight some major progresses made by Chinese research groups in these areas with the selection made merely based on my personal taste. The aim is to let these results better known and appreciated by researchers in the Chinese communities of nanophotonics and related areas, and provide better opportunities of researchers in different areas to have more communications. I also hope that this brief introduction will help to make a better bridge to connect Chinese nanophotonics communities with the broader communities in the world.

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Laser-induced breakdown spectroscopy in Asia
Zhen-Zhen Wang (王珍珍),Yoshihiro Deguchi (出口祥啓),Zhen-Zhen Zhang (张臻臻),Zhe Wang (王哲),Xiao-Yan Zeng (曾晓雁),Jun-Jie Yan (严俊杰)
Frontiers of Physics    2016, 11 (6): 114213-.
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Laser-induced breakdown spectroscopy (LIBS) is an analytical detection technique based on atomic emission spectroscopy to measure the elemental composition. LIBS has been extensively studied and developed due to the non-contact, fast response, high sensitivity, real-time and multi-elemental detection features. The development and applications of LIBS technique in Asia are summarized and discussed in this review paper. The researchers in Asia work on different aspects of the LIBS study in fundamentals, data processing and modeling, applications and instrumentations. According to the current research status, the challenges, opportunities and further development of LIBS technique in Asia are also evaluated to promote LIBS research and its applications.

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Nanomaterials for electrochemical energy storage
Nian Liu, Weiyang Li, Mauro Pasta, Yi Cui
Frontiers of Physics    2014, 9 (3): 323-350.
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The development of nanotechnology in the past two decades has generated great capability of controlling materials at the nanometer scale and has enabled exciting opportunities to design materials with desirable electronic, ionic, photonic, and mechanical properties. This development has also contributed to the advance in energy storage, which is a critical technology in this century. In this article, we will review how the rational design of nanostructured materials has addressed the challenges of batteries and electrochemical capacitors and led to high-performance electrochemical energy storage devices. Four specific material systems will be discussed: i) nanostructured alloy anodes for Li-batteries, ii) nanostructured sulfur cathodes for Li-batteries, iii) nanoporous openframework battery electrodes, and iv) nanostructured electrodes for electrochemical capacitors.

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Simulating cyclotron-Bloch dynamics of a charged particle in a 2D lattice by means of cold atoms in driven quasi-1D optical lattices
Andrey R. Kolovsky
Frontiers of Physics    2012, 7 (1): 3-7.
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Quantum dynamics of a charged particle in a two-dimensional (2D) lattice subject to magnetic and electric fields is a rather complicated interplay between cyclotron oscillations (the case of vanishing electric field) and Bloch oscillations (zero magnetic field), details of which has not yet been completely understood. In the present work we suggest to study this problem by using cold atoms in optical lattices. We introduce a one-dimensional (1D) model which can be easily realized in laboratory experiments with quasi-1D optical lattices and show that this model captures many features of the cyclotron-Bloch dynamics of the quantum particle in 2D square lattices.

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Quadrupolar matter-wave soliton in two-dimensional free space
Jia-Sheng Huang, Xun-Da Jiang, Huai-Yu Chen, Zhi-Wei Fan, Wei Pang, Yong-Yao Li
Frontiers of Physics    2015, 10 (4): 100507-null.
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We study two-dimensional (2D) matter-wave solitons in the mean-field models formed by electric quadrupole particles with long-range quadrupole–quadrupole interaction (QQI) in 2D free space. The existence of 2D matter-wave solitons in the free space was predicted using the 2D Gross–Pitaevskii Equation (GPE). We find that the QQI solitons have a higher mass (smaller size and higher intensity) and stronger anisotropy than the dipole–dipole interaction (DDI) solitons under the same environmental parameters. Anisotropic soliton–soliton interaction between two identical QQI solitons in 2D free space is studied. Moreover, stable anisotropic dipole solitons are observed, to our knowledge, for the first time in 2D free space under anisotropic nonlocal cubic nonlinearity.

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Carrier balance and linear magnetoresistance in type-II Weyl semimetal WTe2
Xing-Chen Pan,Yiming Pan,Juan Jiang,Huakun Zuo,Huimei Liu,Xuliang Chen,Zhongxia Wei,Shuai Zhang,Zhihe Wang,Xiangang Wan,Zhaorong Yang,Donglai Feng,Zhengcai Xia,Liang Li,Fengqi Song,Baigeng Wang,Yuheng Zhang,Guanghou Wang
Frontiers of Physics    2017, 12 (3): 127203-.
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Unsaturated magnetoresistance (MR) has been reported in type-II Weyl semimetal WTe2, manifested as a perfect compensation of opposite carriers. We report linear MR (LMR) in WTe2 crystals, the onset of which was identified by constructing the MR mobility spectra for weak fields. The LMR further increased and became dominant for fields stronger than 20 T, while the parabolic MR gradually decayed. The LMR was also observed in high-pressure conditions.

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A survey of dark matter and related topics in cosmology
Bing-Lin Young
Frontiers of Physics    2017, 12 (2): 121201-.
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This article presents an extensive review of the status of the search of the dark matter. The first eight sections are devoted to topics in dark matter and its experimental searches, and the rest to selected topics in astrophysics and cosmology, which are intended to supply some of the needed background for students in particle physics. Sections 9 and 13 are introductory cosmology. The three astrophysical topics, Big Bang nucleosynthesis Section 10, Boltzmann transport equation and freeze out of massive particles Section 11, and CMB anisotropy Section 12 can all be studied in analytical approaches when reasonable approximations are made. Their original analytically forms, to which this article follows very closely, were given by particle physicists. Dark matter is an evolving subject requiring timely update to stay current. Hence a review of such a subject matter would undoubtedly have something wanting when it appears in print. It is hoped that this review can form a humble basis for those graduate students who would like to pursue the subject of dark matter. The reader can use the extensive table of contents to see in some details the materials covered in the article.

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Novel method to determine effective length of quantum confinement using fractional-dimension space approach
Hua Li, Bing-Can Liu, Bing-Xin Shi, Si-Yu Dong, Qiang Tian
Frontiers of Physics    2015, 10 (4): 107302-null.
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The binding energy and effective mass of a polaron confined in a GaAs film deposited on an AlxGa1-x As substrate are investigated, for different film thickness values and aluminum concentrations and within the framework of the fractional-dimensional space approach. Using this scheme, we propose a new method to define the effective length of the quantum confinement. The limitations of the definition of the original effective well width are discussed, and the binding energy and effective mass of a polaron confined in a GaAs film are obtained. The fractional-dimensional theoretical results are shown to be in good agreement with previous, more detailed calculations based on second-order perturbation theory.

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Towards an understanding of Type Ia supernovae from a synthesis of theory and observations
W. Hillebrandt, M. Kromer, F. K. Röpke, A. J. Ruiter
Frontiers of Physics    2013, 8 (2): 116-143.
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Motivated by the fact that calibrated light curves of Type Ia supernovae (SNe Ia) have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them with observations and we show how such models can be applied to study the origin of the diversity of SNe Ia.

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Quantum coherence, correlations and dynamics of ultracold atoms: From fundamental research to future technology
Chaohong Lee, Peter D. Drummond, Masahito Ueda
Frontiers of Physics    2012, 7 (1): 1-2.
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Quantum spin Hall effect in inverted InAs/GaSb quantum wells
Ivan Knez, Rui-Rui Du
Frontiers of Physics    2012, 7 (2): 200-207.
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We review the recent experimental progress towards observing quantum spin Hall effect in inverted InAs/GaSb quantum wells (QWs). Low temperature transport measurements in the hybridization gap show bulk conductivity of a non-trivial origin, while the length and width dependence of conductance in this regime show strong evidence for the existence of helical edge modes proposed by Liu et al. [Phys. Rev. Lett., 2008, 100: 236601]. Surprisingly, edge modes persist in spite of comparable bulk conduction and show only weak dependence on magnetic field. We elucidate that seeming independence of edge on bulk transport comes due to the disparity in Fermi-wave vectors between the bulk and the edge, leading to a total internal reflection of the edge modes.

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Laser cooling and trapping of ytterbium atoms
Xin-ye XU (徐信业), Wen-li WANG (王文丽), Qing-hong ZHOU (周庆红), Guo-hui LI (李国辉), Hai-ling JIANG (蒋海灵), Lin-fang CHEN (陈林芳), Jie YE (叶捷), Zhi-hong ZHOU (周志红), Yin CAI (蔡寅), Hai-yao TANG (唐海瑶), Min ZHOU (周敏)
Frontiers of Physics in China    2009, 4 (2): 160-164.
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The experiments on the laser cooling and trapping of ytterbium atoms are reported, including the two-dimensional transversal cooling, longitudinal velocity Zeeman deceleration, and a magneto-optical trap with a broadband transition at a wavelength of 399 nm. The magnetic field distributions along the axis of a Zeeman slower were measured and in a good agreement with the calculated results. Cold ytterbium atoms were produced with a number of about 107 and a temperature of a few milli-Kelvin. In addition, using a 556-nm laser, the excitations of cold ytterbium atoms at 1S0-3P1 transition were observed. The ytterbium atoms will be further cooled in a 556-nm magneto-optical trap and loaded into a three-dimensional optical lattice to make an ytterbium optical clock.

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Chemically decorated boron-nitride nanoribbons
Xiao-jun WU, Men-hao WU, Xiao Cheng ZENG
Frontiers of Physics in China    2009, 4 (3): 367-372.
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Motivated by recent studies of graphenen nanoribbons (GNRs), we explored electronic properties of pure and chemically modified boron nitride nanoribbons (BNNRs) using the density functional theory method. Pure BNNRs with both edges fully saturated by hydrogen are semiconducting with wide band gaps. Values of the band gap depend on the width and the type of edge. The chemical decoration of BNNRs’ edges with four different functional groups, including –F, –Cl, –OH, and –NO2, was investigated. The band-gap modulation by chemical decoration may be exploited for nanoelectronic applications.

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Towards graphene nanoribbon-based electronics
Bing HUANG (黄兵), Qi-min YAN (严琪闽), Zuan-yi LI (李缵轶), Wen-hui DUAN (段文晖)
Frontiers of Physics in China    2009, 4 (3): 269-279.
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The successful fabrication of single layer graphene has greatly stimulated the progress of the research on graphene. In this article, focusing on the basic electronic and transport properties of graphene nanoribbons (GNRs), we review the recent progress of experimental fabrication of GNRs, the theoretical and experimental investigations of physical properties, and device applications of GNRs. We also briefly discuss the research efforts on the spin polarization of GNRs in relation to the edge states.

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Effect of thermal annealing on sub-band-gap absorptance of microstructured silicon in air
Cao Li-Ping(曹丽萍), Chen Zhan-Dong(陈战东), Zhang Chun-Ling(张春玲), Yao Jiang-Hong(姚江宏)
Frontiers of Physics    2015, 10 (4): 107801-null.
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The optical absorption properties of femtosecond-laser-made “black silicon” as a function of the annealing conditions were investigated. We found that the annealing process changes the surface morphology and absorption spectroscopy of the “black silicon” samples, and obtained a maximum sub-band-gap absorptance value of approximately 30% by annealing at 1000 °C for 30 min. The thermal relaxation and atomic structural transformation mechanisms are used to describe the lattice recovery and the increase and decrease of the substitutional dopant atom concentration in the microstructured surface during the annealing. Our results confirm that: i) owing to the thermal relaxation, the lattice defects decrease with the increase of the annealing temperature; ii) the quasi-substitutional and interstitial configurations of the doped atoms transform into substitutional arrangements when the annealing temperature increases; iii) the quasi-substitutional and interstitial configurations with higher energies of the doped atoms transform into interstitial configurations with the lowest energy after high-temperature annealing for a long period of time, causing the deactivation or reactivation of the sub-band-gap absorptance by diffusion. The results demonstrate that the annealing can improve the properties of “black silicon”, including defects repairing, carrier lifetime lengthening, and retention of a high absorptive performance.

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Chiral selective tunneling induced graphene nanoribbon switch
Qin-wei SHI (石勤伟), Zheng-fei WANG (王征飞), Qun-xiang LI (李群祥), Jin-long YANG (杨金龙)
Frontiers of Physics in China    2009, 4 (3): 373-377.
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An armchair graphene nanoribbon switch has been designed based on the principle of the Klein paradox. The resulting switch displays an excellent on–off ratio performance. An anomalous tunneling phenomenon, in which electrons do not pass through the graphene nanoribbon junction even when the conventional resonance condition is satisfied, is observed in our numerical simulations. A selective tunneling rule is proposed to explain this interesting transport behavior based on our analytical results. Based on this selective rule, our switch design can also achieve the confinement of an electron to form a quantum qubit.

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Propagation dynamics of finite-energy Airy beams in nonlocal nonlinear media
Zhen-Kun Wu,Peng Li,Yu-Zong Gu
Frontiers of Physics    2017, 12 (5): 124203-.
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We investigate periodic inversion and phase transition of normal and displaced finite-energy Airy beams propagating in nonlocal nonlinear media with the split-step Fourier method. Numerical simulation results show that parameters such as the degree of nonlocality and amplitude have profound effects on the intensity distribution of the period of an Airy beam. Nonlocal nonlinear media will reduce into a harmonic potential if the nonlocality is strong enough, which results in the beam fluctuating in an approximately cosine mode. The beam profile changes from an Airy profile to a Gaussian one at a critical point, and during propagation the process repeats to form an unusual oscillation. We also briefly discus the two-dimensional case, being equivalent to a product of two one-dimensional cases.

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First-principles investigation of structural, mechanical, electronic, and bonding properties of NaZnSb
Jian-Bing Gu, Chen-Ju Wang, Lin Zhang, Yan Cheng, Xiang-Dong Yang
Frontiers of Physics    2015, 10 (4): 107101-null.
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The structural, mechanical, electronic, and bonding properties and phase transition of NaZnSb are explored using the generalized gradient approximation based on ab initio plane-wave pseudopotential density functional theory. With the help of the quasi-harmonic Debye model, we probe the Grüneisen parameter, thermal expansivity, heat capacity, Debye temperature, and entropy of NaZnSb in the tetragonal phase. The results indicate that the lattice constants and the bulk modulus and its first pressure derivative agree well with the available theoretical and experimental data. NaZnSb in its ground state structure exhibits a distinct energy gap of about 0.41 eV, which increases with increasing pressure. Our conclusions are consistent with the theoretical predictions obtained by the ABINIT package, but are different from those obtained through the tight-binding linear muffin-tin orbital method. As a result, further experimental and theoretical researches need to be carried out. For the purpose of providing a comparative and complementary study for future research, we first investigate the thermodynamic properties of NaZnSb.

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Dynamic fragmentation in a quenched two-mode Bose–Einstein condensate
Shu-Yuan Wu (吴淑媛),Hong-Hua Zhong (钟宏华),Jia-Hao Huang (黄嘉豪),Xi-Zhou Qin (秦锡洲),Chao-Hong Lee (李朝红)
Frontiers of Physics    2016, 11 (3): 101204-.
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We investigate the fragmentation in a two-mode Bose–Einstein condensate with Josephson coupling. We explore how the fragmentation and entropy of the ground state depend on the intermode asymmetry and interparticle interactions. Owing to the interplay between the asymmetry and the interactions, a sequence of notches and plateaus in the fragmentation appears with the single-atom tunneling and interaction blockade, respectively. We then analyze the dynamical properties of the fragmentation in three typical quenches of the asymmetry: linear, sudden, and periodic quenches. In a linear quench, the final state is a fragmented state due to the sequential Landau–Zener tunneling, which can be analytically explained by applying the two-level Landau–Zener formula for each avoided level crossing. In a sudden quench, the fragmentation exhibits persistent fluctuations that sensitively depend on the interparticle interactions and intermode coupling. In a periodic quench, the fragmentation is modulated by the periodic driving, and a suitable modulation may allow one to control the fragmentation.

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Progress on tilted axis cranking covariant density functional theory for nuclear magnetic and antimagnetic rotation
Jie Meng (孟杰), Jing Peng (彭婧), Shuang-Quan Zhang (张双全), Peng-Wei Zhao (赵鹏巍)
Frontiers of Physics    2013, 8 (1): 55-79.
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Magnetic rotation and antimagnetic rotation are exotic rotational phenomena observed in weakly deformed or near-spherical nuclei, which are respectively interpreted in terms of the shears mechanism and two shearslike mechanism. Since their observations, magnetic rotation and antimagnetic rotation phenomena have been mainly investigated in the framework of tilted axis cranking based on the pairing plus quadrupole model. For the last decades, the covariant density functional theory and its extension have been proved to be successful in describing series of nuclear ground-states and excited states properties, including the binding energies, radii, single-particle spectra, resonance states, halo phenomena, magnetic moments, magnetic rotation, low-lying excitations, shape phase transitions, collective rotation and vibrations, etc. This review will mainly focus on the tilted axis cranking covariant density functional theory and its application for the magnetic rotation and antimagnetic rotation phenomena.

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