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Coherent Coupling between Microwave and Optical Fields via Cold Atoms
Zhen-Tao Liang, Qing-Xian Lv, Shan-Chao Zhang, Wei-Tao Wu, Yan-Xiong Du, Hui Yan, Shi-Liang Zhu
Chin. Phys. Lett. 2019, 36 (8):
080301
.
DOI: 10.1088/0256-307X/36/8/080301
We demonstrate a long-coherent-time coupling between microwave and optical fields through cold atomic ensembles. The phase information of the microwave field is stored in a coherent superposition state of a cold atomic ensemble and is then read out by two optical fields after 12 ms. A similar operation of mapping the phase of optical fields into a cold atomic ensemble and then retrieving by microwave is also demonstrated. These studies demonstrate that long-coherent-time cold atomic ensembles could resonantly couple with microwave and optical fields simultaneously, which paves the way for realizing high-efficiency, high-bandwidth, and noiseless atomic quantum converters.
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A Quasi-1D Potential for Bose Gas Phase Fluctuations
Shi-Feng Yang, Zi-Tong Xu, Kai Wang, Xiu-Fei Li, Yue-Yang Zhai, Xu-Zong Chen
Chin. Phys. Lett. 2019, 36 (8):
080302
.
DOI: 10.1088/0256-307X/36/8/080302
An elongated trap potential for cold atoms is designed based on a quadrupole-Ioffe configuration. Phase fluctuations in a Bose–Einstein condensate (BEC), which is confined by the trap, are studied. We simulate the atom density distribution induced by fluctuation after time of flight from this elongated trap potential and study the temperature measurement method related to the distribution. Furthermore, taking advantage of the tight confinement and radio frequency dressing technique, we propose a double well potential for splitting BECs. Our results are helpful for improving understanding of low-dimensional quantum gases and provide important guidance for atomic interferometry.
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Oscillation and Migration of Bubbles within Ultrasonic Field
Wen-Hua Wu, Peng-Fei Yang, Wei Zhai, Bing-Bo Wei
Chin. Phys. Lett. 2019, 36 (8):
084302
.
DOI: 10.1088/0256-307X/36/8/084302
The oscillation and migration of bubbles within an intensive ultrasonic field are important issues concerning acoustic cavitation in liquids. We establish a selection map of bubble oscillation mode related to initial bubble radius and driving sound pressure under 20 kHz ultrasound and analyze the individual-bubble migration induced by the combined effects of pressure gradient and acoustic streaming. Our results indicate that the pressure threshold of stable and transient cavitation decreases with the increasing initial bubble radius. At the pressure antinode, the Bjerknes force dominates the bubble migration, resulting in the large bubbles gathering toward antinode center, whereas small bubbles escape from antinode. By contrast, at the pressure node, the bubble migration is primarily controlled by acoustic streaming, which effectively weakens the bubble adhesion on the container walls, thereby enhancing the cavitation effect in the whole liquid.
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Magnetic Sensing inside a Diamond Anvil Cell via Nitrogen-Vacancy Center Spins
Yan-Xing Shang, Fang Hong, Jian-Hong Dai, Hui-Yu, Ya-Nan Lu, En-Ke Liu, Xiao-Hui Yu, Gang-Qin Liu, Xin-Yu Pan
Chin. Phys. Lett. 2019, 36 (8):
086201
.
DOI: 10.1088/0256-307X/36/8/086201
The diamond anvil cell-based high-pressure technique is a unique tool for creating new states of matter and for understanding the physics underlying some exotic phenomena. In situ sensing of spin and charge properties under high pressure is crucially important but remains technically challenging. While the nitrogen-vacancy (NV) center in diamond is a promising quantum sensor under extreme conditions, its spin dynamics and the quantum control of its spin states under high pressure remain elusive. In this study, we demonstrate coherent control, spin relaxation, and spin dephasing measurements for ensemble NV centers up to 32.8 GPa. With this in situ quantum sensor, we investigate the pressure-induced magnetic phase transition of a micron-size permanent magnet Nd$_{2}$Fe$_{14}$B sample in a diamond anvil cell, with a spatial resolution of $\sim$2 μm, and sensitivity of $\sim$20 $\mu$T/Hz$^{1/2}$. This scheme could be generalized to measure other parameters such as temperature, pressure and their gradients under extreme conditions. This will be beneficial for frontier research of condensed matter physics and geophysics.
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Reexploration of Structural Changes in Element Bromine through Pressure-Induced Decomposition of Solid HBr
Ming-Kun Liu, De-Fang Duan, Yan-Ping Huang, Yong-Fu Liang, Xiao-Li Huang, Tian Cui
Chin. Phys. Lett. 2019, 36 (8):
086401
.
DOI: 10.1088/0256-307X/36/8/086401
Simple molecular solids have been an important subject in condensed matter physics, particularly for research of pressure-induced molecular dissociation. We re-explore the structural changes of element bromine through pressure-induced decomposition of solid HBr. The phase changes in HBr are investigated by Raman spectroscopy and synchrotron x-ray diffraction up to 125 GPa at room temperature. By applying pressure, HBr decomposes into solid bromine in the pressure range of 18.7–38 GPa. The solid bromine changes from molecular phase to incommensurate phase at 81 GPa, and finally to monatomic phase at 91 GPa. During the process of pressure-induced molecular dissociation, the intermediate incommensurate phase of element bromine is confirmed for the first time from the x-ray diffraction studies. The decomposition of HBr is irreversible since HBr cannot form again upon pressure decompression.
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Superconductivity in Topological Semimetal $\theta$-TaN at High Pressure
Ya-Ting Jia, Jian-Fa Zhao, Si-Jia Zhang, Shuang Yu, Guang-Yang Dai, Wen-Min Li, Lei Duan, Guo-Qiang Zhao, Xian-Cheng Wang, Xu Zheng, Qing-Qing Liu, You-Wen Long, Zhi Li, Xiao-Dong Li, Hong-Ming Weng, Run-Ze Yu, Ri-Cheng Yu, Chang-Qing Jin
Chin. Phys. Lett. 2019, 36 (8):
087401
.
DOI: 10.1088/0256-307X/36/8/087401
Recently, $\theta$-TaN was proposed to be a topological semimetal with a new type of triply degenerate nodal points. Here, we report studies of pressure dependence of transport, Raman spectroscopy and synchrotron x-ray diffraction on $\theta$-TaN up to 61 GPa. We find that $\theta$-TaN becomes superconductive above 24.6 GPa with $T_{\rm c}$ at 3.1 K. The $\theta$-TaN is of n-type carrier nature with carrier density about $1.1\times 10^{20}$/cm$^{3}$ at 1.2 GPa and 20 K, while the carrier density increases with the pressure and saturates at about 40 GPa in the measured range. However, there is no crystal structure transition with pressure up to 39 GPa, suggesting the topological nature of the pressure induced superconductivity.
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Fabrication and Characterization of GaN-Based Micro-LEDs on Silicon Substrate
Qi Wang, Jun-Chi Yu, Tao Tao, Bin Liu, Ting Zhi, Xu Cen, Zi-Li Xie, Xiang-Qian Xiu, Yu-Gang Zhou, You-Dou Zheng, Rong Zhang
Chin. Phys. Lett. 2019, 36 (8):
088501
.
DOI: 10.1088/0256-307X/36/8/088501
GaN-based micro light emitting diodes (micro-LEDs) on silicon (Si) substrates with 40 μm in diameter are developed utilizing standard photolithography and inductively coupled plasma etching techniques. From current-voltage curves, the relatively low turn-on voltage of 2.8 V and low reverse leakage current in the order of 10$^{-8}$ A/cm$^{2}$ indicate good electrical characteristics. As the injection current increases, the electroluminescence emission wavelength hardly shifts at around 433 nm, and the relative external quantum efficiency slightly decays, because the impact of quantum-confined Stark effect is not serious in violet-blue micro-LEDs. Since GaN-LEDs are cost effective on large-area Si and suitable for substrate transfer or vertical device structures, the fabricated micro-LEDs on Si should have promising applications in the fields of high-resolution display and optical communication.
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Erratum: Experimental Realization of an Intrinsic Magnetic Topological Insulator [Chin. Phys. Lett. 36(2019)076801]
Yan Gong, Jingwen Guo, Jiaheng Li, Kejing Zhu, Menghan Liao, Xiaozhi Liu, Qinghua Zhang, Lin Gu, Lin Tang, Xiao Feng, Ding Zhang, Wei Li, Canli Song, Lili Wang, Pu Yu, Xi Chen, Yayu Wang, Hong Yao, Wenhui Duan, Yong Xu , Shou-Cheng Zhang, Xucun Ma, Qi-Kun Xue , Ke He
Chin. Phys. Lett. 2019, 36 (8):
089901
.
DOI: 10.1088/0256-307X/36/8/089901
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20 articles
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