Please wait a minute...
For Selected: View Abstracts Toggle Thumbnails
Symmetry-Protected Scattering in Non-Hermitian Linear Systems
L. Jin and Z. Song
Chin. Phys. Lett.    2021, 38 (2): 024202 .   DOI: 10.1088/0256-307X/38/2/024202
Abstract   HTML   PDF (2449KB)
Symmetry plays fundamental role in physics and the nature of symmetry changes in non-Hermitian physics. Here the symmetry-protected scattering in non-Hermitian linear systems is investigated by employing the discrete symmetries that classify the random matrices. The even-parity symmetries impose strict constraints on the scattering coefficients: the time-reversal ($C$ and $K$) symmetries protect the symmetric transmission or reflection; the pseudo-Hermiticity ($Q$ symmetry) or the inversion ($P$) symmetry protects the symmetric transmission and reflection. For the inversion-combined time-reversal symmetries, the symmetric features on the transmission and reflection interchange. The odd-parity symmetries including the particle-hole symmetry, chiral symmetry, and sublattice symmetry cannot ensure the scattering to be symmetric. These guiding principles are valid for both Hermitian and non-Hermitian linear systems. Our findings provide fundamental insights into symmetry and scattering ranging from condensed matter physics to quantum physics and optics.
A Search for Solar Axions and Anomalous Neutrino Magnetic Moment with the Complete PandaX-II Data
Xiaopeng Zhou, Xinning Zeng, Xuyang Ning, Abdusalam Abdukerim, Wei Chen, Xun Chen, Yunhua Chen, Chen Cheng, Xiangyi Cui, Yingjie Fan, Deqing Fang, Changbo Fu, Mengting Fu, Lisheng Geng, Karl Giboni, Linhui Gu, Xuyuan Guo, Ke Han, Changda He, Di Huang, Yan Huang, Yanlin Huang, Zhou Huang, Xiangdong Ji, Yonglin Ju, Shuaijie Li, Huaxuan Liu, Jianglai Liu, Xiaoying Lu, Wenbo Ma, Yugang Ma, Yajun Mao, Yue Meng, Kaixiang Ni, Jinhua Ning, Xiangxiang Ren, Changsong Shang, Guofang Shen, Lin Si, Andi Tan, Anqing Wang, Hongwei Wang, Meng Wang, Qiuhong Wang, Siguang Wang, Wei Wang, Xiuli Wang, Zhou Wang, Mengmeng Wu, Shiyong Wu, Weihao Wu, Jingkai Xia, Mengjiao Xiao, Pengwei Xie, Binbin Yan, Jijun Yang, Yong Yang, Chunxu Yu, Jumin Yuan, Ying Yuan, Dan Zhang, Tao Zhang, Li Zhao, Qibin Zheng, Jifang Zhou, and Ning Zhou (PandaX-II Collaboration)
Chin. Phys. Lett.    2021, 38 (1): 011301 .   DOI: 10.1088/0256-307X/38/1/011301
Abstract   HTML   PDF (764KB)
We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-II, in light of the recent event excess reported by XENON1T. The data correspond to a total exposure of 100.7 ton$\cdot$day with liquid xenon. With robust estimates of the dominant background spectra, we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment. It is found that the axion-electron coupling $g_{\rm Ae} < 4.6\times 10^{-12}$ for an axion mass less than 0.1 keV/$c^2$ and the neutrino magnetic moment $\mu_{\nu} < 4.9\times 10^{-11}\mu_{\rm B}$ at 90% confidence level. The observed excess from XENON1T is within our experimental constraints.
Dynamic Crossover in Metallic Glass Nanoparticles
Shan Zhang, Weihua Wang, and Pengfei Guan
Chin. Phys. Lett.    2021, 38 (1): 016802 .   DOI: 10.1088/0256-307X/38/1/016802
Abstract   HTML   PDF (2203KB)
We report the dynamic crossover behavior in metallic glass nanoparticles (MGNs) with the size reduction based on the extensive molecular dynamics (MD) simulations combined with the activation-relaxation technique (ART). The fragile-to-strong transition of dynamics can be achieved by just modulating the characteristic size of MGNs. It can be attributed to the abnormal fast surface dynamics enhanced by the surface curvature. By determining the potential energy surface, we reveal the hierarchy-to-flat transition of potential energy landscape (PEL) in MGNs, and demonstrate the intrinsic flat potential landscape feature of the MGN with size smaller than a critical size. Our results provide an important piece of the puzzle about the size-modulated potential energy landscape and shed some lights on the unique properties of MGs in nanoscale.
Accurate Evaluation on the Interactions of SARS-CoV-2 with Its Receptor ACE2 and Antibodies CR3022/CB6
Hong-ming Ding, Yue-wen Yin, Song-di Ni, Yan-jing Sheng, and Yu-qiang Ma
Chin. Phys. Lett.    2021, 38 (1): 018701 .   DOI: 10.1088/0256-307X/38/1/018701
Abstract   HTML   PDF (1775KB)
The spread of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a global health crisis. The binding affinity of SARS-CoV-2 (in particular the receptor binding domain, RBD) to its receptor angiotensin converting enzyme 2 (ACE2) and the antibodies is of great importance in understanding the infectivity of COVID-19 and evaluating the candidate therapeutic for COVID-19. We propose a new method based on molecular mechanics/Poisson–Boltzmann surface area (MM/PBSA) to accurately calculate the free energy of SARS-CoV-2 RBD binding to ACE2 and antibodies. The calculated binding free energy of SARS-CoV-2 RBD to ACE2 is $-13.3$ kcal/mol, and that of SARS-CoV RBD to ACE2 is $-11.4$ kcal/mol, which agree well with the experimental results of $-11.3$ kcal/mol and $-10.1$ kcal/mol, respectively. Moreover, we take two recently reported antibodies as examples, and calculate the free energy of antibodies binding to SARS-CoV-2 RBD, which is also consistent with the experimental findings. Further, within the framework of the modified MM/PBSA, we determine the key residues and the main driving forces for the SARS-CoV-2 RBD/CB6 interaction by the computational alanine scanning method. The present study offers a computationally efficient and numerically reliable method to evaluate the free energy of SARS-CoV-2 binding to other proteins, which may stimulate the development of the therapeutics against the COVID-19 disease in real applications.
Strain Tunable Berry Curvature Dipole, Orbital Magnetization and Nonlinear Hall Effect in WSe$_{2}$ Monolayer
Mao-Sen Qin , Peng-Fei Zhu , Xing-Guo Ye , Wen-Zheng Xu , Zhen-Hao Song , Jing Liang , Kaihui Liu , and Zhi-Min Liao
Chin. Phys. Lett.    2021, 38 (1): 017301 .   DOI: 10.1088/0256-307X/38/1/017301
Abstract   HTML   PDF (2896KB)
The electronic topology is generally related to the Berry curvature, which can induce the anomalous Hall effect in time-reversal symmetry breaking systems. Intrinsic monolayer transition metal dichalcogenides possesses two nonequivalent $K$ and $K'$ valleys, having Berry curvatures with opposite signs, and thus vanishing anomalous Hall effect in this system. Here we report the experimental realization of asymmetrical distribution of Berry curvature in a single valley in monolayer WSe$_2$ via applying uniaxial strain to break $C_{3v}$ symmetry. As a result, although the Berry curvature itself is still opposite in $K$ and $K'$ valleys, the two valleys would contribute equally to nonzero Berry curvature dipole. Upon applying electric field ${\boldsymbol E}$, the emergent Berry curvature dipole ${\boldsymbol D}$ would lead to an out-of-plane orbital magnetization $M \propto {\boldsymbol D} \cdot {\boldsymbol E}$, which further induces an anomalous Hall effect with a linear response to $E^2$, known as nonlinear Hall effect. We show the strain modulated transport properties of nonlinear Hall effect in monolayer WSe$_2$ with moderate hole-doping by gating. The second-harmonic Hall signals show quadratic dependence on electric field, and the corresponding orbital magnetization per current density $M/J$ can reach as large as 60. In contrast to the conventional Rashba–Edelstein effect with in-plane spin polarization, such current-induced orbital magnetization is along the out-of-plane direction, thus promising for high-efficient electrical switching of perpendicular magnetization.
How Does van der Waals Confinement Enhance Phonon Transport?
Xiaoxiang Yu, Dengke Ma, Chengcheng Deng, Xiao Wan, Meng An, Han Meng, Xiaobo Li, Xiaoming Huang, and Nuo Yang
Chin. Phys. Lett.    2021, 38 (1): 014401 .   DOI: 10.1088/0256-307X/38/1/014401
Abstract   HTML   PDF (2162KB)
We study the mechanism of van der Waals (vdW) interactions on phonon transport in atomic scale, which would boost developments in heat management and energy conversion. Commonly, the vdW interactions are regarded as a hindrance in phonon transport. Here we propose that the vdW confinement can enhance phonon transport. Through molecular dynamics simulations, it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon. The quantitative analyses of morphology, local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism. It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes, leading to less phonon scattering and facilitating thermal transport. Our study offers a new strategy to modulate the phonon transport.
Classical-Noise-Free Sensing Based on Quantum Correlation Measurement
Ping Wang , Chong Chen , and Ren-Bao Liu
Chin. Phys. Lett.    2021, 38 (1): 010301 .   DOI: 10.1088/0256-307X/38/1/010301
Abstract   HTML   PDF (791KB)
Quantum sensing, using quantum properties of sensors, can enhance resolution, precision, and sensitivity of imaging, spectroscopy, and detection. An intriguing question is: Can the quantum nature (quantumness) of sensors and targets be exploited to enable schemes that are not possible for classical probes or classical targets? Here we show that measurement of the quantum correlations of a quantum target indeed allows for sensing schemes that have no classical counterparts. As a concrete example, in the case that the second-order classical correlation of a quantum target could be totally concealed by non-stationary classical noise, the higher-order quantum correlations can single out a quantum target from the classical noise background, regardless of the spectrum, statistics, or intensity of the noise. Hence a classical-noise-free sensing scheme is proposed. This finding suggests that the quantumness of sensors and targets is still to be explored to realize the full potential of quantum sensing. New opportunities include sensitivity beyond classical approaches, non-classical correlations as a new approach to quantum many-body physics, loophole-free tests of the quantum foundation, et cetera.
BaCuS$_{2}$: A Superconductor with Moderate Electron-Electron Correlation
Yuhao Gu, Xianxin Wu, Kun Jiang, and Jiangping Hu
Chin. Phys. Lett.    2021, 38 (1): 017501 .   DOI: 10.1088/0256-307X/38/1/017501
Abstract   HTML   PDF (4790KB)
We show that the layered-structure BaCuS$_{2}$ is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors. Theoretical calculations reveal that the in-plane $d$–$p$ $\sigma^*$-bonding bands are isolated near the Fermi level. As the energy separation between the $d$ and $p$ orbitals are much smaller than those in cuprates and iron-based superconductors, BaCuS$_{2}$ is expected to be moderately correlated. We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms, namely the conventional BCS electron-phonon interaction and the electron-electron correlation, which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.
Exciton Vortices in Two-Dimensional Hybrid Perovskite Monolayers
Yingda Chen, Dong Zhang, and Kai Chang
Chin. Phys. Lett.    2020, 37 (11): 117102 .   DOI: 10.1088/0256-307X/37/11/117102
Abstract   HTML   PDF (1191KB)
We study theoretically the exciton Bose–Einstein condensation and exciton vortices in a two-dimensional (2D) perovskite (PEA)${_2}$PbI${_4}$ monolayer. Combining the first-principles calculations and the Keldysh model, the exciton binding energy of in a (PEA)${_2}$PbI${_4}$ monolayer can approach hundreds of meV, which make it possible to observe the excitonic effect at room temperature. Due to the large exciton binding energy, and hence the high density of excitons, we find that the critical temperature of the exciton condensation could approach the liquid nitrogen regime. In the presence of perpendicular electric fields, the dipole-dipole interaction between excitons is found to drive the condensed excitons confined in (PEA)${_2}$PbI${_4}$ monolayer flakes into patterned vortices, as the evolution time of vortex patterns is comparable to the exciton lifetime.
Reaction Rate Weighted Multilayer Nuclear Reaction Network
Huan-Ling Liu, Ding-Ding Han, Peng Ji, and Yu-Gang Ma
Chin. Phys. Lett.    2020, 37 (11): 112601 .   DOI: 10.1088/0256-307X/37/11/112601
Abstract   HTML   PDF (1233KB)
Nuclear reaction rate $\lambda$ is a significant factor in processes of nucleosyntheses. A multi-layer directed-weighted nuclear reaction network, in which the reaction rate is taken as the weight, and neutron, proton, $^4$He and the remainder nuclei as the criteria for different reaction layers, is for the first time built based on all thermonuclear reactions in the JINA REACLIB database. Our results show that with the increase in the stellar temperature $T_{9}$, the distribution of nuclear reaction rates on the R-layer network demonstrates a transition from unimodal to bimodal distributions. Nuclei on the R-layer in the region of $\lambda = [1,2.5\times10^{1}]$ have a more complicated out-going degree distribution than that in the region of $\lambda = [10^{11},10^{13}]$, and the number of involved nuclei at $T_{9} = 1$ is very different from the one at $T_{9} = 3$. The redundant nuclei in the region of $\lambda = [1, 2.5\times10^{1}]$ at $T_{9} = 3$ prefer $(\gamma,{\rm p})$ and $({\gamma,\alpha})$ reactions to the ones at $T_{9}=1$, which produce nuclei around the $\beta$ stable line. This work offers a novel way to the big-data analysis on the nuclear reaction network at stellar temperatures.
Page 1 of 12 115 records