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Probing a Dissipative Phase Transition with a Trapped Ion through Reservoir Engineering
M.-L. Cai, Z.-D. Liu, Y. Jiang, Y.-K. Wu, Q.-X. Mei, W.-D. Zhao, L. He, X. Zhang, Z.-C. Zhou, and L.-M. Duan
Chin. Phys. Lett. 2022, 39 (2):
020502
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DOI: 10.1088/0256-307X/39/2/020502
Dissipation is often considered as a detrimental effect in quantum systems for unitary quantum operations. However, it has been shown that suitable dissipation can be useful resources in both quantum information and quantum simulation. Here, we propose and experimentally simulate a dissipative phase transition (DPT) model using a single trapped ion with an engineered reservoir. We show that the ion's spatial oscillation mode reaches a steady state after the alternating application of unitary evolution under a quantum Rabi model Hamiltonian and sideband cooling of the oscillator. The average phonon number of the oscillation mode is used as the order parameter to provide evidence for the DPT. Our work highlights the suitability of trapped ions for simulating open quantum systems and shall facilitate further investigations of DPT with various dissipation terms.
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High Temperature Melting Curve of Basaltic Glass by Laser Flash Heating
Yukai Zhuang, Junwei Li, Wenhua Lu, Xueping Yang, Zhixue Du, and Qingyang Hu
Chin. Phys. Lett. 2022, 39 (2):
020701
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DOI: 10.1088/0256-307X/39/2/020701
Basalt is an igneous rock originating from the cooling and solidification of magma and covers approximately 70% of Earth's surface. Basaltic glass melting in the deep Earth is a fundamental subject of research for understanding geophysics, geochemistry, and geodynamic processes. In this study, we design a laser flash heating system using two-dimensional, four-color multi-wavelength imaging radiometry to measure the basaltic glass melting temperature under high pressure conditions in diamond anvil cells. Our experiment not only determines the temperature at the center of heating but also constructs a temperature distribution map for the surface heating area, and enables us to assess the temperature gradient. Through precise temperature measurements, we observe that the basaltic glass melting temperature is higher than those in previous reports, which is near the normal upper-mantle isotherm, approaching the hot geotherm. This suggests that basalt should not melt in most of the normal upper mantle and the basaltic melts could exist in some hot regions.
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Identification of Above-Threshold Ionization by Imaging Photoelectrons from Ammonia Molecules in an Intense Femtosecond Laser Field
Qin Yang, Jing Leng, Yan-Hui Wang, Ya-Nan Sun, Hai-Bin Du, Dong-Dong Zhang, Le-Le Song, Lan-Hai He, and Fu-Chun Liu
Chin. Phys. Lett. 2022, 39 (2):
023301
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DOI: 10.1088/0256-307X/39/2/023301
The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from $1.6 \times 10^{13}$ to $5.7 \times 10^{13}$ W/cm$^{2}$. Channel switching under different laser intensities is observed and identified in the photoelectron kinetic energy spectra of ammonia. Based on the photoelectron kinetic energy distributions and the photoelectron angular distributions, the characteristic peaks observed are exclusively assigned to the multiphoton resonance through certain intermediate states, followed by multiphoton above-threshold ionization.
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First-Principles Calculations about Elastic and Li$^{+}$ Transport Properties of Lithium Superoxides under High Pressure and High Temperature
Yufeng Li, Shichuan Sun, Yu He, and Heping Li
Chin. Phys. Lett. 2022, 39 (2):
026101
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DOI: 10.1088/0256-307X/39/2/026101
Lithium superoxides, Li$_{2}$O$_{3}$, LiO$_{2}$, and LiO$_{4}$, have been synthesized under high pressure. These materials have potential applications in energy storage devices. Here, we use first-principles calculations to investigate the elastic and Li$^{+}$ transport properties of these oxides at high pressure and high temperature. The elastic constants are calculated at 20–80 GPa, and they satisfy the Born stability criteria, indicating the good mechanical stability of these oxides. Their sound velocities calculated with elastic constants are close to each other, but difference in velocity anisotropy is obvious. LiO$_{2}$ presents significant shear sound wave anisotropy over 80%. The Li$^{+}$ transport properties are investigated using first principles molecular dynamics (FPMD) and climbing-image nudged elastic band methods. The lowest Li$^{+}$ migration barrier energies increase from 0.93, 0.86 and 1.22 eV at 20 GPa to 1.43, 1.12 and 1.77 eV at 50 GPa for Li$_{2}$O$_{3}$, LiO$_{2}$, and LiO$_{4}$, respectively. The most favorable path for LiO$_{2}$ and LiO$_{4}$ is along the [001] direction. The FPMD results suggest that these oxides become unstable with increasing temperature up to 2000 K due to O–O dimer clusters in these superoxides. Consequently, a superionic transition is not observed in the simulations.
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Evidence for a High-Pressure Isostructural Transition in Nitrogen
Chunmei Fan, Shan Liu, Jingyi Liu, Binbin Wu, Qiqi Tang, Yu Tao, Meifang Pu, Feng Zhang, Jianfu Li, Xiaoli Wang, Duanwei He, Chunyin Zhou, and Li Lei
Chin. Phys. Lett. 2022, 39 (2):
026401
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DOI: 10.1088/0256-307X/39/2/026401
We observed an isostructural phase transition in the solid nitrogen $\lambda$-N$_{2}$ at approximately 50 GPa accompanied by anomalies in lattice parameters, atomic volume and Raman vibron modes. The anomalies are ascribed to a slight reorientation of the nitrogen molecules, which does not seem to affect the monoclinic symmetry (space group $P2_{1}/c$). Our ab initio calculations further confirm the phenomena, and suggest an optimized structure for the $\lambda$-N$_{2}$ phase. In addition, a new high-pressure amorphous phase of $\eta '$-N$_{2}$ was also discovered by a detailed investigation of the pressure-temperature phase diagram of nitrogen with the aim of probing the phase stability of $\lambda$-N$_{2}$. Our result may provide helpful information about the crystallographic nature of dissociation transitions in diatomic molecular crystals (H$_{2}$, O$_{2}$, N$_{2}$, etc).
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Superconductivity with a Violation of Pauli Limit and Evidences for Multigap in $\eta$-Carbide Type Ti$_4$Ir$_2$O
Bin-Bin Ruan, Meng-Hu Zhou, Qing-Song Yang, Ya-Dong Gu, Ming-Wei Ma, Gen-Fu Chen, and Zhi-An Ren
Chin. Phys. Lett. 2022, 39 (2):
027401
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DOI: 10.1088/0256-307X/39/2/027401
We report the synthesis, crystal structure, and superconductivity of Ti$_4$Ir$_2$O. The title compound crystallizes in an $\eta$-carbide type structure of the space group $Fd\bar{3}m$ (No. 227), with lattice parameters $a=b=c=11.6194(1)$ Å. The superconducting temperature $T_{\rm c}$ is found to be 5.1–5.7 K. Most surprisingly, Ti$_4$Ir$_2$O hosts an upper critical field of 16.45 T, which is far beyond the Pauli paramagnetic limit. Strong coupled superconductivity with evidences for multigap is revealed by the measurements of heat capacity and upper critical field. First-principles calculations suggest that the density of states near the Fermi level originates from the hybridization of Ti-3$d$ and Ir-5$d$ orbitals, and the effect of spin-orbit coupling on the Fermi surfaces is prominent. Large values of the Wilson ratio ($R_{\rm W} \sim 3.9$), the Kadowaki–Woods ratio [$A/\gamma^2 \sim 9.0 \times 10^{-6}$ $µ\Omega\cdot$cm/(mJ$\cdot$mol$^{-1}\cdot$K$^{-1}$)$^2$], and the Sommerfeld coefficient ($\gamma = 33.74$ mJ$\cdot$mol$^{-1}\cdot$K$^{-2}$) all suggest strong electron correlations (similar to heavy fermion systems) in Ti$_4$Ir$_2$O. The violation of Pauli limit is possibly due to a combination of strong-coupled superconductivity and large spin-orbit scattering. With these intriguing behaviors, Ti$_4$Ir$_2$O serves as a candidate for unconventional superconductor.
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Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate $\alpha$-RuCl$_3$
Kejing Ran, Jinghui Wang, Song Bao, Zhengwei Cai, Yanyan Shangguan, Zhen Ma, Wei Wang, Zhao-Yang Dong, P. Čermák, A. Schneidewind, Siqin Meng, Zhilun Lu, Shun-Li Yu, Jian-Xin Li, and Jinsheng Wen
Chin. Phys. Lett. 2022, 39 (2):
027501
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DOI: 10.1088/0256-307X/39/2/027501
It is known that $\alpha$-RuCl$_3$ has been studied extensively because of its proximity to the Kitaev quantum-spin-liquid (QSL) phase and the possibility of approaching it by tuning the competing interactions. Here we present the first polarized inelastic neutron scattering study on $\alpha$-RuCl$_3$ single crystals to explore the scattering continuum around the $\varGamma$ point at the Brillouin zone center, which was hypothesized to be resulting from the Kitaev QSL state but without concrete evidence. With polarization analyses, we find that, while the spin-wave excitations around the $M$ point vanish above the transition temperature $T_{\rm N}$, the pure magnetic continuous excitations around the $\varGamma$ point are robust against temperature. Furthermore, by calculating the dynamical spin-spin correlation function using the cluster perturbation theory, we derive magnetic dispersion spectra based on the $K$–$\varGamma$ model, which involves with a ferromagnetic Kitaev interaction of $-7.2$ meV and an off-diagonal interaction of $5.6$ meV. We find this model can reproduce not only the spin-wave excitation spectra around the $M$ point, but also the non-spin-wave continuous magnetic excitations around the $\varGamma$ point. These results provide evidence for the existence of fractional excitations around the $\varGamma$ point originating from the Kitaev QSL state, and further support the validity of the $K$–$\varGamma$ model as the effective minimal spin model to describe $\alpha$-RuCl$_3$.
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Wet Mechanical Milling Induced Phase Transition to Cubic Anti-Perovskite Li$_{2}$OHCl
Di-Xing Ni, Yao-Dong Liu, Zhi Deng, Dian-Cheng Chen, Xin-Xin Zhang, Tao Wang, Shuai Li, and Yu-Sheng Zhao
Chin. Phys. Lett. 2022, 39 (2):
028201
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DOI: 10.1088/0256-307X/39/2/028201
Anti-perovskite solid-state electrolyte Li$_{2}$OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature. However, its ionic conductivity increases greatly when the temperature is up to 40 ℃, while it goes through an orthorhombic-to-cubic phase transition. The cubic Li$_{2}$OHCl with high ionic conductivity is stabilized at room temperature and even lower temperature about 10 ℃ by a simple synthesis method of wet mechanical milling. The cubic Li$_{2}$OHCl prepared by this method performs an ionic conductivity of $4.27 \times 10^{-6}$ S/cm at room temperature, about one order of magnitude higher than that of the orthorhombic Li$_{2}$OHCl. The phase-transition temperature is decreased to around 10 ℃. Moreover, it can still remain cubic phase after heat treatment at 210 ℃. This work delivers a huge potential of fabricating high ionic conductivity phase anti-perovskite solid-state electrolyte materials by wet mechanical milling.
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Electrochemical Role of Transition Metals in Sn–Fe Alloy Revealed by Operando Magnetometry
Le-Qing Zhang, Qing-Tao Xia, Zhao-Hui Li, Yuan-Yuan Han, Xi-Xiang Xu, Xin-Long Zhao, Xia Wang, Yuan-Yuan Pan, Hong-Sen Li, and Qiang Li
Chin. Phys. Lett. 2022, 39 (2):
028202
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DOI: 10.1088/0256-307X/39/2/028202
As promising materials, alloy-type anode materials have been intensively investigated in both academia and industry. To release huge volume expansion during alloying/dealloying process, they are usually doped with transition metals. However, the electrochemical role of transition metals has not been fully understood. Here, pure Sn$_{3}$Fe films were deposited by sputtering, and the electrochemical mechanism was systematically investigated by operando magnetometry. We confirmed that Fe particles liberated by Li insertion recombine partially with Sn during the delithiation, while the stepwise increase in magnetization with the cycles demonstrates growth of Fe nanoparticles. In addition, we also found an unconventional increase of magnetization in the charging process, which can be attributed to the space charge storage at the interface of Fe/Li$_{x}$Sn. These critical findings pave the way for the mechanism understanding and development of high-performance Sn based alloy electrode materials.
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15 articles
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