Frontiers of Physics

ISSN 2095-0462

ISSN 2095-0470(Online)

CN 11-5994/O4

2018 Impact Factor: 2.483

封面图片   2019年, 第14卷 第5期
Artificial and periodically modulated optical structure realizes the possibility for tailoring the diffraction and dispersion properties of light. Electromagnetically induced grating (EIG) is constructed by replacing the traveling wave field of electromagnetically induced transparency with a standing-wave field, the atomic coherence of medium is mo [展开] ...
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2019年, 第14卷 第5期 出版日期:2019-10-15

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Perfect optical nonreciprocity in a double-cavity optomechanical system
Xiao-Bo Yan, He-Lin Lu, Feng Gao, Feng Gao, Liu Yang
Frontiers of Physics. 2019, 14 (5): 52601-.  
https://doi.org/10.1007/s11467-019-0922-3

摘要   PDF (847KB)

Nonreciprocal devices are indispensable for building quantum networks and ubiquitous in modern communication technology. Here, we propose to take advantage of the interference between optomechanical interaction and linearly-coupled interaction to realize optical nonreciprocal transmission in a double-cavity optomechanical system. Particularly, we have derived essential conditions for perfect optical nonreciprocity and analysed properties of the optical nonreciprocal transmission. These results can be used to control optical transmission in quantum information processing.

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Entanglement and excited-state quantum phase transition in an extended Dicke model
Gui-Lei Zhu, Xin-You Lü, Shang-Wu Bin, Cai You, Ying Wu
Frontiers of Physics. 2019, 14 (5): 52602-.  
https://doi.org/10.1007/s11467-019-0921-4

摘要   PDF (3816KB)

We investigate the properties of entanglement and excited-state quantum phase transition (ESQPT) in a hybrid atom-optomechanical system in which an optomechanical quadratic interaction is introduced into a normal Dicke model. Interestingly, by preparing the ancillary mode in a coherent state, both the quantum entanglement and ESQPT can be realized in a relative weak-coupling condition. Moreover, the entanglement is immune to the A2 term, and a reversed trend of the entropy is obtained when the A2 term is included. Density of states (DoS) and Peres lattice are used to investigate ESQPTs. Compared to a normal Dicke model, the DoS enlarges exp(2rα) times if the ancillary mode is prepared in a coherent state. This work is an extension of the ground-state quantum phase transition, which may inspire further exploration of the quantum criticality in many-body systems.

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Controllable electromagnetically induced grating in a cascade-type atomic system
Jin-Peng Yuan, Chao-Hua Wu, Yi-Hong Li, Li-Rong Wang, Yun Zhang, Lian-Tuan Xiao, Suo-Tang Jia
Frontiers of Physics. 2019, 14 (5): 52603-.  
https://doi.org/10.1007/s11467-019-0924-1

摘要   PDF (2409KB)

A controllable electromagnetically induced grating (EIG) is experimentally realized in a coherent rubidium ensemble with 5S1/2–5P3/2–5D5/2 cascade configuration. In our work, a whole picture describing the relation between the first-order diffraction efficiency and the power of the coupling field is experimentally presented for the first time, which agrees well with the theoretical prediction. More important, by fine tuning the experimental parameters, the first-order diffraction efficiency of as high as 25% can be achieved and a clear three-order diffraction pattern is also observed. Such a controllable periodic structure can provide a powerful tool for studying the control of light dynamics, pave the way for realizing new optical device.

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Recent advances in controlling the crystallization of two-dimensional perovskites for optoelectronic device
Shi-Qiang Luo, Ji-Fei Wang, Bin Yang, Yong-Bo Yuan
Frontiers of Physics. 2019, 14 (5): 53401-.  
https://doi.org/10.1007/s11467-019-0901-8

摘要   PDF (2407KB)

Though three-dimensional (3D) organic–inorganic halide perovskites (OIHP) is very promising for low cost and distributed PV generation, the stability issue of 3D OIHP is still a problem for its commercialization. Two-dimensional (2D) perovskites, protected by periodic organic ligands, is promising due to its excellent optoelectronic property and superior stability. However, 2D perovskite is anisotropic in its crystal structure and optoelectronic properties, and the resulted film is often a mixture of different phase. So, methods to manipulate 2D perovskite crystal orientation and its phase separation are vital. In this review, the major advances on the composition engineering, crystal orientation, phase separation, and interfacial capping are summarized. Besides, efforts on understanding the formation process of 2D perovskite crystal are also discussed, which is important for making full use of 2D perovskite in functional optoelectronic devices.

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Rational design of photoelectrodes for photoelectrochemical water splitting and CO2 reduction
Yu Hui Lui, Bowei Zhang, Shan Hu
Frontiers of Physics. 2019, 14 (5): 53402-.  
https://doi.org/10.1007/s11467-019-0903-6

摘要   PDF (6359KB)

Solar energy has promising potential for building sustainable society. Conversion of solar energy into solar fuels plays a crucial role in overcoming the intermittent nature of the renewable energy source. A photoelectrochemical (PEC) cell that employs semiconductor as photoelectrode to split water into hydrogen or fixing carbon dioxide (CO2) into hydrocarbon fuels provides great potential to achieve zero-carbon-emission society. A proper design of these semiconductor photoelectrodes thus directly influences the performance of the PEC cell. In this review, we investigate the strategies that have been put towards the design of efficient photoelectrodes for PEC water splitting and CO2 reduction in recent years and provide some future design directions toward next-generation PEC cells for water splitting and CO2 reduction.

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The impact of crystal defects towards oxide semiconductor photoanode for photoelectrochemical water splitting
Qi-Tao Liu, De-Yu Liu, Jian-Ming Li, Yong-Bo Kuang
Frontiers of Physics. 2019, 14 (5): 53403-.  
https://doi.org/10.1007/s11467-019-0905-4

摘要   PDF (6835KB)

Photoelectrochemical (PEC) water oxidation for sustainable clean energy and fuel production is a potential solution to the demands of organic pollutant removal and growing energy consumption. Development of high performance photoanodes, which is a key component in the system, is one of the central topics in the area. The crystal defect is an old concept but fruiting new understanding with promotive impact to the development of high performance photoanodes. In this review, we elucidated the typical defects involved in the photoanode with the position where they play the roles in the structure and how the properties of photoanode are influenced. In addition, we summarized the feasible protocols to maximize the pros but reduce the cons brought by having defects to the photoanode performance based on recent most prominent research advancements in the field. Finally, we briefly sketched the future perspective with the challenges of this topic when in the scenario of possible developments into practical applications.

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Possible phase transition of anisotropic frustrated Heisenberg model at finite temperature
Ai-Yuan Hu, Lin Wen, Guo-Pin Qin, Zhi-Min Wu, Peng Yu, Yu-Ting Cui
Frontiers of Physics. 2019, 14 (5): 53601-.  
https://doi.org/10.1007/s11467-019-0895-2

摘要   PDF (1645KB)

The frustrated spin-1/2 J1aJ1bJ2 antiferromagnet with anisotropy on the two-dimensional square lattice was investigated, where the parameters J1aand J1b represent the nearest neighbor exchanges and along the x and y directions, respectively. J2 represents the next-nearest neighbor exchange. The anisotropy includes the spatial and exchange anisotropies. Using the double-time Green’s function method, the effects of the interplay of exchanges and anisotropy on the possible phase transition of the Néel state and stripe state were discussed. Our results indicated that, in the case of anisotropic parameter 0≤η<1, the Néel and stripe states can exist and have the same critical temperature as long as J2 = J1b/2. Under such parameters, a first-order phase transformation between the Néel and stripe states can occur below the critical point. For J2J1b/2, our results indicate that the Néel and stripe states can also exist, while their critical temperatures differ. When J2>J1b/2, a first-order phase transformation between the two states may also occur. However, for J2<J1b/2, the Néel state is always more stable than the stripe state.

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Skyrmion Hall effect with spatially modulated Dzyaloshinskii–Moriya interaction
Liping Zhou, Ren Qin, Ya-Qing Zheng, Yong Wang
Frontiers of Physics. 2019, 14 (5): 53602-.  
https://doi.org/10.1007/s11467-019-0897-0

摘要   PDF (1469KB)

The skyrmion Hall effect is theoretically studied in the chiral ferromagnetic film with spatially modulated Dzyaloshinskii–Moriya interaction. Three cases including linear, sinusoidal, and periodic rectangular modulations have been considered, where the increase, decrease, and the periodic modification of the size and velocity of the skyrmion have been observed in the microscopic simulations. These phenomena are well explained by the Thiele equation, where an effective force on the skyrmion is induced by the inhomogeneous Dzyaloshinskii–Moriya interaction. The results here suggest that the skyrmion Hall effect can be manipulated by artificially tuning the Dzyaloshinskii–Moriya interaction in chiral ferromagnetic film with material engineering methods, which will be useful to design skyrmion-based spintronics devices.

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High-order exceptional points in non-Hermitian Moiré lattices
Yan-Rong Zhang, Ze-Zheng Zhang, Jia-Qi Yuan, Ming Kang, Jing Chen
Frontiers of Physics. 2019, 14 (5): 53603-.  
https://doi.org/10.1007/s11467-019-0899-y

摘要   PDF (2675KB)

This study proposes an approach to generate high-order exceptional points (EPs) in non-Hermitian systems. A system comprising a homogenous waveguide is considered wherein the imaginary part of the refractive index is modulated using a one-dimensional Moiré profile. This gain-loss modulation couples different lossless waveguide modes, and these hybrid modes can be modeled using a non-Hermitian matrix with complex off-diagonal elements. Results indicate that third-order EPs can be produced by the coalescence of two second-order EPs. Then, the necessary requirements are analyzed using coupled-wave equations and the physical effects of the singularities are discussed.

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β-PtO2: Phononic, thermodynamic, and elastic properties derived from first-principles calculations
Quan Chen (陈泉), Wei Li (李伟), Yong Yang (杨勇)
Frontiers of Physics. 2019, 14 (5): 53604-.  
https://doi.org/10.1007/s11467-019-0900-9

摘要   PDF (2744KB)

β-PtO2 is a useful transition metal dioxide, but its fundamental thermodynamic and elastic properties remain unexplored. Using first-principles calculations, we systematically studied the structure, phonon, thermodynamic and elastic properties of β-PtO2. The lattice dynamics and structural stability of β-PtO2 under pressure were studied using the phonon spectra and vibrational density of states. The vibrational frequencies of the optical modes of β-PtO2 increase with elevating pressure; this result is comparable with the available experimental data. Then, the heat capacities and their pressure responses were determined based on the phonon calculations. The pressure dependence of the Debye temperature was studied, and the results were compared in two distinct aspects. The elastic moduli of β-PtO2 were estimated through the Voigt–Reuss–Hill approximation. The bulk modulus of β-PtO2 increases linearly with pressure, but the shear modulus is nearly independent of pressure. Our study revealed that the elastic stiffness coefficients C44, C55 and C66 play a primary role in the slow variation of the shear modulus.

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Comment to “Dynamics of supercooled confined water measured by deep inelastic neutron scattering”
Y. Finkelstein, R. Moreh
Frontiers of Physics. 2019, 14 (5): 53605-.  
https://doi.org/10.1007/s11467-019-0926-z

摘要   PDF (661KB)

We comment on the findings of “Dynamics of supercooled confined water measured by deep inelastic neutron scattering”, by V. De Michele, G. Romanelli, and A. Cupane [Front. Phys. 13, 138205 (2018)]. We show that the current sensitivity of the deep inelastic neutron scattering (DINS) method, cannot detect with confidence small differences in the proton kinetic energy, Ke(H), involved in a liquid-liquid transition in supercooled water confined in nanoporous silica. We also critisize the calculation of Ke(H) carried out in Front. Phys. 13, 138205 (2018).

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Reply to “Comment to ‘Dynamics of supercooled confined water measured by deep inelastic neutron scattering’ by Y. Finkelstein and R. Moreh”
V. De Michele, G. Romanelli, A. Cupane
Frontiers of Physics. 2019, 14 (5): 53606-.  
https://doi.org/10.1007/s11467-019-0927-y

摘要   PDF (542KB)

We reply to the comment [Front. Phys. 14(5), 53605 (2019)] by Y. Finkelstein and R. Moreh on our article Front. Phys. 13(1), 138205 (2018). We agree with some of their criticisms about our calculation of the temperature effect on the kinetic energy of hydrogen atoms of supercooled confined water; we also agree with their statement that, in view of the current sensitivity of the technique, possible effects of the liquid–liquid water transition are hardly detected with deep inelastic neutron scattering (DINS). However, we disagree with their use of the translational mass ratio of a single water molecule and, in general, with their underestimation of collective effects.

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