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Molecular Nature of $X(3872)$ in $B^0 \to K^0 X(3872)$ and $B^+ \to K^+ X(3872)$ Decays
Hao-Nan Wang, Li-Sheng Geng, Qian Wang, and Ju-Jun Xie
Chin. Phys. Lett. 2023, 40 (2):
021301
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DOI: 10.1088/0256-307X/40/2/021301
We investigate the decays of $B^0 \to K^0 X(3872)$ and $B^+ \to K^+ X(3872)$ based on the picture where the $X(3872)$ resonance is strongly coupled to the $D\bar{D}^* + c.c.$ channel. In addition to the decay mechanism where the $X(3872)$ resonance is formed from the $c\bar{c}$ pair hadronization with the short-distance interaction, we have also considered the $D\bar{D}^*$ rescattering diagrams in the long-distance scale, where $D$ and $\bar{D}^*$ are formed from $c$ and $\bar{c}$ separately. Because of the difference of the mass thresholds of charged and neutral $D\bar{D}^*$ channels, and the rather narrow width of the $X(3872)$ resonance, at the $X(3872)$ mass, the loop functions of $D^0\bar{D}^{*0}$ and $D^+\bar{D}^{*-}$ are much different. Taking this difference into account, the ratio of $\mathcal{B}[B^0\to K^0X(3872)]/\mathcal{B}[B^+ \to K^+ X(3872)] \simeq 0.5$ can be naturally obtained. Based on this result, we also evaluate the decay widths of $B_s^0 \to \eta(\eta') X(3872)$. It is expected that future experimental measurements of these decays can be used to elucidate the nature of the $X(3872)$ resonance.
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Tunable Dual-Wavelength Fiber Laser in a Novel High Entropy van der Waals Material
Wen-Wen Cui, Xiao-Wei Xing, Yue-Qian Chen, Yue-Jia Xiao, Han Ye, and Wen-Jun Liu
Chin. Phys. Lett. 2023, 40 (2):
024201
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DOI: 10.1088/0256-307X/40/2/024201
Fiber lasers with different net dispersion cavity values can produce some types of solitons, and rich nonlinear dynamics phenomena can be achieved by selecting different saturable absorbers. A new layered high-entropy van der Waals material (HEX) (Mn,Fe,Co,Ni)PS$_{3}$ was selected as a saturable absorber to achieve a high-power laser output of 34 mW. In addition, the wavelength can be dynamically tuned from 1560 nm to 1531 nm with significant dual-wavelength phenomena at 460 fs pulse duration.
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Anomalous Second Magnetization Peak in 12442-Type RbCa$_2$Fe$_4$As$_4$F$_2$ Superconductors
Xiaolei Yi, Xiangzhuo Xing, Yan Meng, Nan Zhou, Chunlei Wang, Yue Sun, and Zhixiang Shi
Chin. Phys. Lett. 2023, 40 (2):
027401
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DOI: 10.1088/0256-307X/40/2/027401
The second magnetization peak (SMP) appears in most superconductors and is crucial for the understanding of vortex physics as well as the application. Although it is well known that the SMP is related to the type and quantity of disorder/defects, the mechanism has not been universally understood. We selected three stoichiometric superconducting RbCa$_2$Fe$_4$As$_4$F$_2$ single crystals with identical superconducting critical temperature $T_{\rm c} \sim 31$ K and similar self-field critical current density $J_{\rm c}$, but with different amounts of disorder/defects, to study the SMP effect. It is found that only the sample S2 with moderate disorder/defects shows significant SMP effect. The evolution of the normalized pinning force density $f_{\rm p}$ demonstrates that the dominant pinning mechanism changes from the weak pinning at low temperatures to strong pinning at high temperatures. The microstructure study for sample S2 reveals some expanded Ca$_2$F$_2$ layers and dislocation defects in RbFe$_2$As$_2$ layers. The normalized magnetic relaxation results indicate that the SMP is strongly associated with the elastic to plastic (E-P) vortex transition. As temperature increases, the SMP gradually evolves into a step-like shape and then becomes a sharp peak near the irreversibility field similar to what is usually observed in low-temperature superconductors. Our findings connect the low field SMP of high-temperature superconductors and the high field peak of low-temperature superconductors, revealing the possible universal origin related to the E-P phase transition.
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Framework for Contrastive Learning Phases of Matter Based on Visual Representations
Xiao-Qi Han, Sheng-Song Xu, Zhen Feng, Rong-Qiang He, and Zhong-Yi Lu
Chin. Phys. Lett. 2023, 40 (2):
027501
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DOI: 10.1088/0256-307X/40/2/027501
A main task in condensed-matter physics is to recognize, classify, and characterize phases of matter and the corresponding phase transitions, for which machine learning provides a new class of research tools due to the remarkable development in computing power and algorithms. Despite much exploration in this new field, usually different methods and techniques are needed for different scenarios. Here, we present SimCLP: a simple framework for contrastive learning phases of matter, which is inspired by the recent development in contrastive learning of visual representations. We demonstrate the success of this framework on several representative systems, including non-interacting and quantum many-body, conventional and topological. SimCLP is flexible and free of usual burdens such as manual feature engineering and prior knowledge. The only prerequisite is to prepare enough state configurations. Furthermore, it can generate representation vectors and labels and hence help tackle other problems. SimCLP therefore paves an alternative way to the development of a generic tool for identifying unexplored phase transitions.
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Topological Magnons in Kitaev Magnets with Finite Dzyaloshinskii–Moriya Interaction at High Field
Kangkang Li
Chin. Phys. Lett. 2023, 40 (2):
027502
.
DOI: 10.1088/0256-307X/40/2/027502
There have been intensive studies on Kitaev materials for the sake of realization of exotic states such as quantum spin liquid and topological orders. In realistic materials, the Kitaev interaction may coexist with the Dzyaloshinskii–Moriya interaction, and it is of challenge to distinguish their magnitudes separately. Here, we study the topological magnon excitations and related thermal Hall conductivity of kagome magnet exhibiting Heisenberg, Kitaev and Dzyaloshinskii–Moriya interactions exposed to a magnetic field. In a strong magnetic field perpendicular to the plane of the lattice ([111] direction) that brings the system into a fully polarized paramagnetic phase, we find that the magnon bands carry nontrivial Chern numbers in the full region of the phase diagram. Furthermore, there are phase transitions related to two topological phases with opposite Chern numbers, which lead to the sign changes of the thermal Hall conductivity. In the phase with negative thermal conductivity, the Kitaev interaction is relatively large and the width of the phase increases with the strength of Dzyaloshinskii–Moriya interaction. Hence, the present study will contribute to the understanding of related compounds.
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Low-Temperature Aqueous Na-Ion Batteries: Strategies and Challenges of Electrolyte Design
Qiubo Guo, Shuai Han, Yaxiang Lu, Liquan Chen, and Yong-Sheng Hu
Chin. Phys. Lett. 2023, 40 (2):
028801
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DOI: 10.1088/0256-307X/40/2/028801
Aqueous Na-ion batteries (ANIBs) are considered to be promising secondary battery systems for grid-scale energy storage applications and have attracted widespread attention due to their unique merits of rich resources of Na, as well as the inherent safety and low cost of aqueous electrolytes. However, the narrow electrochemical stability widow and high freezing point of traditional dilute aqueous electrolytes restrict their multi-scenario applications. Considering the charge-storage mechanism of ANIBs, the optimization and design of aqueous Na-based electrolytes dominate their low-temperature performance, which is also hot off the press in this field. In this review, we first systematically comb the research progress of the novel electrolytes and point out their remaining challenges in ANIBs. Then our perspectives on how to further improve the low-temperature performance of ANIBs will also be discussed. Finally, this review briefly sheds light on the potential direction of low-temperature ANIBs, which would guide the future design of high-performance aqueous rechargeable batteries.
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Erratum: Evidence of Electronic Phase Separation in the Strongly Correlated Semiconductor YbB$_{12}$ [Chin. Phys. Lett. 39, 127302 (2022)]
A. Azarevich, N. Bolotina, O. Khrykina, A. Bogach, E. Zhukova, B. Gorshunov, A. Melentev, Z. Bedran, A. Alyabyeva, M. Belyanchikov, V. Voronov, N. Yu. Shitsevalova, V. B. Filipov, and N. Sluchanko
Chin. Phys. Lett. 2023, 40 (2):
029901
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DOI: 10.1088/0256-307X/40/2/029901
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Erratum: Frustrated Magnetic Interactions and Quenched Spin Fluctuations in CrAs [Chin. Phys. Lett. 39, 127501 (2022)]
Yayuan Qin, Yao Shen, Yiqing Hao, Hongliang Wo, Shoudong Shen, Russell A. Ewings, Yang Zhao, Leland W. Harriger, Jeffrey W. Lynn, and Jun Zhao
Chin. Phys. Lett. 2023, 40 (2):
029902
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DOI: 10.1088/0256-307X/40/2/029902
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13 articles
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