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Enhanced phase sensitive amplification towards improving noise immunity Hui Guo(郭辉), Zhi Li(李治), Hengxin Sun(孙恒信), Kui Liu(刘奎), and Jiangrui Gao(郜江瑞) Chin. Phys. B, 2023, 32 (5): 054204.   DOI: 10.1088/1674-1056/acbdeb Abstract （141）   HTML （12）    PDF （1960KB）（130）       Knowledge map    Quantum states are essential resource for quantum-enhanced applications. Loss incurred in the distribution channel, however, dissipates the high signal-to-noise ratio advantage enjoyed by the squeezed state. Here, we first demonstrate noise immunity enhancement by using phase-sensitive amplifier (PSA) with measurement-based noiseless linear amplifier (MB-NLA). We explore the signal transfer capability with the amplifier in a noisy channel. The MB-NLA enhanced PSA has obvious suppression effect on channel noises, especially it has improvement for the noise contaminated signal. Better performance can be achieved by flexibly adjusting amplifier parameters. With the amplifier, it is promising to overcome the entanglement-distribution loss and show its superiority in squeezing based quantum sensing.

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Stability of the topological quantum critical point between multi-Weyl semimetal and band insulator Zhao-Kun Yang(杨兆昆), Jing-Rong Wang(王景荣), and Guo-Zhu Liu(刘国柱) Chin. Phys. B, 2023, 32 (5): 056401.   DOI: 10.1088/1674-1056/acbaf2 Abstract （69）   HTML （5）    PDF （1702KB）（56）       Knowledge map    One could tune a topological double-Weyl semimetal or a topological triple-Weyl semimetal to become a topologically trivial insulator by opening a band gap. This kind of quantum phase transition is characterized by the change of certain topological invariant. A new gapless semimetallic state emerges at each topological quantum critical point. Here we perform a renormalization group analysis to investigate the stability of such critical points against perturbations induced by random scalar potential and random vector potential. We find that the quantum critical point between double-Weyl semimetal and band insulator is unstable and can be easily turned into a compressible diffusive metal by any type of weak disorder. The quantum critical point between triple-Weyl semimetal and band insulator flows to a stable strong-coupling fixed point if the system contains a random vector potential merely along the z-axis, but becomes a compressible diffusive metal when other types of disorders exist.

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Visualizing interface states in In2Se3–WSe2 monolayer lateral heterostructures Da Huo(霍达), Yusong Bai(白玉松), Xiaoyu Lin(林笑宇), Jinghao Deng(邓京昊), Zemin Pan(潘泽敏), Chao Zhu(朱超), Chuansheng Liu(刘传胜), and Chendong Zhang(张晨栋) Chin. Phys. B, 2023, 32 (5): 056803.   DOI: 10.1088/1674-1056/acbaef Abstract （51）   HTML （3）    PDF （1539KB）（32）       Knowledge map    Recent findings of two-dimensional (2D) ferroelectric (FE) materials provide more possibilities for the development of 2D FE heterostructure electronic devices based on van der Waals materials and the application of FE devices under the limit of atomic layer thickness. In this paper, we report the in-situ fabrication and probing of electronic structures of In$_{2}$Se$_{3}$-WSe$_{2}$ lateral heterostructures, compared with most vertical FE heterostructures at present. Through molecular beam epitaxy, we fabricated lateral heterostructures with monolayer WSe$_{2}$ (three atomic layers) and monolayer In$_{2}$Se$_{3}$ (five atomic layers). Type-II band alignment was found to exist in either the lateral heterostructure composed of anti-FE $\beta '$-In$_{2}$Se$_{3}$ and WSe$_{2}$ or the lateral heterostructure composed of FE $\beta^*$-In$_{2}$Se$_{3}$ and WSe$_{2}$, and the band offsets could be modulated by ferroelectric polarization. More interestingly, interface states in both lateral heterostructures acted as narrow gap quantum wires, and the band gap of the interface state in the $\beta^*$-In$_{2}$Se$_{3}$-WSe$_{2}$ heterostructure was smaller than that in the $\beta '$-In$_{2}$Se$_{3}$ heterostructure. The fabrication of 2D FE heterostructure and the modulation of interface state provide a new platform for the development of FE devices.

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Prediction of LiCrTe2 monolayer as a half-metallic ferromagnet with a high Curie temperature Li-Man Xiao(肖丽蔓), Huan-Cheng Yang(杨焕成), and Zhong-Yi Lu(卢仲毅) Chin. Phys. B, 2023, 32 (5): 057505.   DOI: 10.1088/1674-1056/acbe2e Abstract （62）   HTML （5）    PDF （2878KB）（33）       Knowledge map    By using first-principles electronic structure calculations, we predict a new two-dimensional half-metallic ferromagnet (2DHMF) with distorted square structure, i.e., the LiCrTe2 monolayer. The results show that the LiCrTe2 monolayer is dynamically, thermally, and mechanically stable, and takes a large in-plane magnetic anisotropy, a wide spin gap, a large magnetization, and a very high Curie temperature. Under a biaxial strain ranging from -5% to +5%, the ferromagnetism, half-metallicity, and high Curie temperature are maintained well. Both tensile and compressive strains can significantly increase the magnitude of the magnetocrystalline anisotropy energy (MAE) and a transition from in-plane easy-x(y)-axis to out-of-plane easy-z-axis occurs when the compressive strain exceeds 1%. Our systematic study of the LiCrTe2 monolayer enables its promising applications in spintronics.

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Spin reorientation in easy-plane kagome ferromagnet Li9Cr3(P2O7)3(PO4)2 Yuanhao Dong(董元浩), Ying Fu(付盈), Yixuan Liu(刘以轩), Zhanyang Hao(郝占阳), Le Wang(王乐), Cai Liu(刘才), Ke Deng(邓可), and Jiawei Mei(梅佳伟) Chin. Phys. B, 2023, 32 (5): 057506.   DOI: 10.1088/1674-1056/acc2b3 Abstract （40）   HTML （8）    PDF （1666KB）（62）       Knowledge map    We report the successful growth and characterization of Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ single crystal, and investigate its magnetic properties under external magnetic fields via magnetization and heat capacity measurements. Our study reveals that Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ is an easy-plane kagome ferromagnet with $S=3/2$, as evidenced by the Curie-Weiss temperature of 6 K which implies a ferromagnetic exchange coupling in the material. Under zero magnetic field, Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ undergoes a magnetic transition at $T_{\rm C} = 2.7$ K from a paramagnetic state to a ferromagnetically ordered state with the magnetic moment lying in the kagome plane. By applying a $c$-axis directional magnetic field to rotate the spin alignment from the kagome plane to the $c$-axis, we observe a reduction in the magnetic transition temperature as the field is increased. We construct a magnetic phase diagram as a function of temperature and magnetic field applied parallel to the $c$-axis of Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ and find that the phase boundary is linear over a certain temperature range. Regarding that theoretically, the field-induced phase transition of the spin reorientation in the easy-plane ferromagnet can be viewed as the ferromagnetic magnon Bose-Einstein condensation (BEC), the phase boundary scaling of field-induced ($B \parallel c$) magnetic transition in Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ can be described as the quasi-2D magnon BEC, which has been observed in other ferromagnetic materials such as K$_2$CuF$_4$.

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Strong spin frustration and magnetism in kagomé antiferromagnets LnCu3(OH)6Br3 (Ln=Nd, Sm, and Eu) Jin-Qun Zhong(钟金群), Zhen-Wei Yu(余振伟), Xiao-Yu Yue(岳小宇), Yi-Yan Wang(王义炎), Hui Liang(梁慧), Yan Sun(孙燕), Dan-Dan Wu(吴丹丹), Zong-Ling Ding(丁宗玲), Jin Sun(孙进), Xue-Feng Sun(孙学峰), and Qiu-Ju Li(李秋菊) Chin. Phys. B, 2023, 32 (4): 047505.   DOI: 10.1088/1674-1056/acb9e8 Abstract （300）   HTML （155）    PDF （2462KB）（317）       Knowledge map    To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties, we grew high-quality single crystals of $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ ($Ln={\rm Nd}$, Sm, and Eu) by hydrothermal method and studied their crystal structures and magnetic properties. The refinements of the crystal structure referred to the powder x-ray diffraction data show that $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ adopt a Kapellasite-type layer structure, which is isostructural to their chlorine analogue. Magnetic susceptibilities demonstrate that $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ have strong antiferromagnetic coupling and a pronounced magnetic frustration effect. Magnetization measurements indicate canted antiferromagnetic ordering of Cu$^{2+}$ ions around 16 K within the kagomé plane and weak ferromagnetic coupling. Moreover, shoulder-like anomalies in specific heat around 16 K could be a signature of emergent of magnetic ordering. The low-temperature negative magnetization and specific heat of $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ ($Ln={\rm Nd}$, Sm, and Eu) indicate that $Ln^{3+}$ ions induce more exotic magnetic ground state properties.

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Tunable phonon-atom interaction in a hybrid optomechanical system Yao Li(李耀), Chuang Li(李闯), Jiandong Zhang(张建东), Ying Dong(董莹), and Huizhu Hu(胡慧珠) Chin. Phys. B, 2023, 32 (4): 044213.   DOI: 10.1088/1674-1056/acb9ea Abstract （252）   HTML （18）    PDF （738KB）（205）       Knowledge map    We theoretically analyze a hybrid system consisting of a levitated neutral atom and a nanoparticle coupled to a cavity. The mechanical oscillator and the atom are effectively coupled to each other through the cavity photons as a bus. By adjusting the driving lasers, we can conveniently switch the phonon-atom coupling between Jaynes-Cummings (JC) and anti-JC forms, which can be used to manipulate the motional states of the mechanical oscillator. As an application, we prepare a superposition state of the mechanical oscillator via the effective phonon-atom interaction and investigate the effects of dissipation on the state generation.

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Modeling of thermal conductivity for disordered carbon nanotube networks Hao Yin(殷浩), Zhiguo Liu(刘治国), and Juekuan Yang(杨决宽) Chin. Phys. B, 2023, 32 (4): 044401.   DOI: 10.1088/1674-1056/acb0be Abstract （119）   HTML （5）    PDF （861KB）（66）       Knowledge map    Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube (CNT) networks. However, these models overestimated the thermal conductivity significantly. In this paper, we claimed that a CNT network can be considered as a contact thermal resistance network. In the contact thermal resistance network, the temperature of an individual CNT is nonuniform and the intrinsic thermal resistance of CNTs can be ignored. Compared with the previous models, the model we proposed agrees well with the experimental results of single-walled CNT networks.

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Conductive path and local oxygen-vacancy dynamics: Case study of crosshatched oxides Z W Liang(梁正伟), P Wu(吴平), L C Wang(王利晨), B G Shen(沈保根), and Zhi-Hong Wang(王志宏) Chin. Phys. B, 2023, 32 (4): 047303.   DOI: 10.1088/1674-1056/acb421 Abstract （115）   HTML （6）    PDF （3660KB）（60）       Knowledge map    By employing scanning probe microscopy, conductive path and local oxygen-vacancy dynamics have been investigated in crosshatched La0.7Sr0.3MnO3 thin films grown onto flat and vicinal LaAlO3(001) single crystal substrates. Consistent with prior studies, the crosshatch topography was observed first by dynamical force microscopy as the epi-stain started to release with increasing film thickness. Second, by using conductive atomic force microscopy (CAFM), conductive crosshatch and dots (locally aligned or random) were unravelled, however, not all of which necessarily coincided with that shown in the in situ atomic force microscopy. Furthermore, the current-voltage responses were probed by CAFM, revealing the occurrence of threshold and/or memristive switchings. Our results demonstrate that the resistive switching relies on the evolution of the local profile and concentration of oxygen vacancies, which, in the crosshatched films, are modulated by both the misfit and threading dislocations.

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Effects of phonon bandgap on phonon-phonon scattering in ultrahigh thermal conductivity θ-phase TaN Chao Wu(吴超) and Chenhan Liu(刘晨晗) Chin. Phys. B, 2023, 32 (4): 046502.   DOI: 10.1088/1674-1056/acb201 Abstract （105）   HTML （8）    PDF （2411KB）（91）       Knowledge map    Phonon bandgap typically has a significant effect on phonon-phonon scattering process. In this work, the effects of mass modified phonon bandgap in θ -phase TaN are systemically investigated by the means of first-principles calculations with linearized Boltzmann transport equation. Through detailed calculations, we find that phonon bandgap has a significant effect on three-phonon process while exhibits a much weaker effect on four-phonon process. The reason for the ultrahigh thermal conductivity of θ -phase TaN is the long lifetime of phonons including both three-phonon and four-phonon processes, which originates from the weak phonon anharmonicity and large phonon bandgap-induced small phonon-phonon scattering phase space. This work advances the understanding of phonon bandgap effects on phonon transport.

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Reconstruction and functionalization of aerogels by controlling mesoscopic nucleation to greatly enhance macroscopic performance Chen-Lu Jiao(焦晨璐), Guang-Wei Shao(邵光伟), Yu-Yue Chen(陈宇岳), and Xiang-Yang Liu(刘向阳) Chin. Phys. B, 2023, 32 (3): 038103.   DOI: 10.1088/1674-1056/acb912 Abstract （435）   HTML （19）    PDF （7614KB）（445）       Knowledge map    This work presents a strategy for the mesoscopic engineering of hierarchically structured sodium alginate (SA) aerogels to enhance the macroscopic performance. The strategy was implemented by meso-functionalizing and reorganizing SA aerogels via controlled heterogeneous nucleation, in which microcrystalline cellulose-manganese dioxide (MCC-MnO2) nano-crystallites worked as template. Due to the short rod-like structure and abundant hydroxyl groups of MCC-MnO2, the organized mesostructure of SA aerogels was reconstructed during the assembly of SA molecule chains, which gave rise to a significant enhancement in macroscopic performance of SA areogels. For instance, the functionalized and reconstructed MCC-MnO2/SA aerogels acquired a more than 70% increase in mechanical strength with an excellent deformation recovery. Furthermore, an almost double enhancement of removal capacity for metal ions (i.e., Cu2+ and Pb2+) and organic dyes (i.e., congo red and methylene blue) was obtained for MnO2/SA aerogels, with an 87% repossession of the pollutants removal performance after 5 operation cycles.

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Transition frequencies between 2S and 2P states of lithium-like ions Liming Wang(王黎明), Tongtong Liu(刘仝彤), Weiqing Yang(杨为青), and Zong-Chao Yan Chin. Phys. B, 2023, 32 (3): 033102.   DOI: 10.1088/1674-1056/acad6f Abstract （195）   HTML （1）    PDF （584KB）（199）       Knowledge map    The Schrödinger equation for the $2$S and $2$P states of the lithium-like ions $Z=5$-7, 9-10 is solved by using the Rayleigh-Ritz variational method in Hylleraas coordinates. The leading-order relativistic and QED corrections are calculated perturbatively and higher-order corrections are estimated. The transition frequencies between the $2{\rm S}_{1/2}$ and $2{\rm P}_J$ ($J=1/2, 3/2$) states are determined and compared with experimental and other theoretical results. Specifically, isotope shifts are also calculated for B$^{2+}$.

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Superconductivity in epitaxially grown LaVO3/KTaO3(111) heterostructures Yuan Liu(刘源), Zhongran Liu(刘中然), Meng Zhang(张蒙), Yanqiu Sun(孙艳秋), He Tian(田鹤), and Yanwu Xie(谢燕武) Chin. Phys. B, 2023, 32 (3): 037305.   DOI: 10.1088/1674-1056/acac1b Abstract （242）   HTML （0）    PDF （1230KB）（211）       Knowledge map    Complex oxide heterointerfaces can host a rich of emergent phenomena, and epitaxial growth is usually at the heart of forming these interfaces. Recently, a strong crystalline-orientation-dependent two-dimensional superconductivity was discovered at interfaces between KTaO3 single-crystal substrates and films of other oxides. Unexpectedly, rare of these oxide films was epitaxially grown. Here, we report the existence of superconductivity in epitaxially grown LaVO3/KTaO3(111) heterostructures, with a superconducting transition temperature of ～ 0.5 K. Meanwhile, no superconductivity was detected in the (001)- and (110)-orientated LaVO3/KTaO3 heterostructures down to 50 mK. Moreover, we find that for the LaVO3/KTaO3(111) interfaces to be conducting, an oxygen-deficient growth environment and a minimum LaVO3 thickness of ～ 0.8 nm (～ 2 unit cells) are needed.

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Bismuth doping enhanced tunability of strain-controlled magnetic anisotropy in epitaxial Y3Fe5O12(111) films Yunpeng Jia(贾云鹏), Zhengguo Liang(梁正国), Haolin Pan(潘昊霖), Qing Wang(王庆), Qiming Lv(吕崎鸣), Yifei Yan(严轶非), Feng Jin(金锋), Dazhi Hou(侯达之), Lingfei Wang(王凌飞), and Wenbin Wu(吴文彬) Chin. Phys. B, 2023, 32 (2): 027501.   DOI: 10.1088/1674-1056/ac67cc Abstract （426）   HTML （3）    PDF （893KB）（336）       Knowledge map    Y3Fe5O12 (YIG) and BiY2Fe5O12 (Bi:YIG) films were epitaxially grown on a series of (111)-oriented garnet substrates using pulsed laser deposition. Structural and ferromagnetic resonance characterizations demonstrated the high epitaxial quality, extremely low magnetic loss and coherent strain state in these films. Using these epitaxial films as model systems, we systematically investigated the evolution of magnetic anisotropy (MA) with epitaxial strain and chemical doping. For both the YIG and Bi:YIG films, the compressive strain tends to align the magnetic moment in the film plane while the tensile strain can compete with the demagnetization effect and stabilize perpendicular MA. We found that the strain-induced lattice elongation/compression along the out-of-plane [111] axis is the key parameter that determines the MA. More importantly, the strain-induced tunability of MA can be enhanced significantly by Bi doping; meanwhile, the ultralow damping feature persists. We clarified that the cooperation between strain and chemical doping could realize an effective control of MA in garnet-type ferrites, which is essential for spintronic applications.

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A novel monoclinic phase and electrically tunable magnetism of van der Waals layered magnet CrTe2 Qidi Ren(任启迪), Kang Lai(赖康), Jiahao Chen(陈家浩), Xiaoxiang Yu(余晓翔), and Jiayu Dai(戴佳钰) Chin. Phys. B, 2023, 32 (2): 027201.   DOI: 10.1088/1674-1056/ac9b37 Abstract （262）   HTML （1）    PDF （1943KB）（184）       Knowledge map    Exploring the novel structural phase of van der Waals (vdW) magnets would promote the development of spintronics. Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrTe2, which is one of the popular vdW magnets normally exhibiting a trigonal structure. The new monoclinic phase emerges from a switchable magnetic state between ferromagnetism and antiferromagnetism through changing hole doping concentration, which suggests a practical approach to obtain such a structure. The results of phonon dispersion and energy analysis convince us that the monoclinic structure is a metastable phase even without hole doping. When the hole doping concentration increases, the stability analysis indicates the preference for a novel monoclinic phase rather than a conventional trigonal phase, and meanwhile, the magnetic properties are accordingly tuned. This work provides new insights into the phase engineering of the chalcogenide family and the electrical control of magnetism of vdW layered magnets.

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Magnetic triangular bubble lattices in bismuth-doped yttrium iron garnet Tao Lin(蔺涛), Chengxiang Wang(王承祥), Zhiyong Qiu(邱志勇), Chao Chen(陈超), Tao Xing(邢弢), Lu Sun(孙璐), Jianhui Liang(梁建辉), Yizheng Wu(吴义政), Zhong Shi(时钟), and Na Lei(雷娜) Chin. Phys. B, 2023, 32 (2): 027505.   DOI: 10.1088/1674-1056/aca604 Abstract （256）   HTML （3）    PDF （2430KB）（177）       Knowledge map    Magnetic bubbles have again become a subject of significant attention following the experimental observation of topologically nontrivial magnetic skyrmions. In recent work, tailoring the shape of the bubbles is considered a key factor for their dynamics in spintronic devices. In addition to the reported circular, elliptical, and square bubbles, here we observe triangular bubble domains in bismuth-doped yttrium iron garnet (Bi-YIG) using Kerr microscopy. The bubble domains evolve from discrete circular to latticed triangular and hexagonal shapes. Further, the orientation of the triangular bubbles in the hexagonal lattices can be flipped by decreasing the magnetic field. The sixfold in-plane magnetic anisotropy of Bi-YIG(111) crystal, which is presumably the mechanism underlying the triangular shape of the bubbles, is measured as 1179 erg/cm3. The study of the morphologies of topologically trivial bubbles in YIG offers insight into nontrivial spin textures, which is appealing for future spintronic applications.

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Different roles of surfaces' interaction on lattice mismatched/matched surfaces in facilitating ice nucleation Xuanhao Fu(傅宣豪) and Xin Zhou(周昕) Chin. Phys. B, 2023, 32 (2): 028202.   DOI: 10.1088/1674-1056/aca202 Abstract （193）   HTML （0）    PDF （4059KB）（129）       Knowledge map    The freezing of water is one of the most common processes in nature and affects many aspects of human activity. Ice nucleation is a crucial part of the freezing process and usually occurs on material surfaces. There is still a lack of clear physical pictures about the central question how various features of material surfaces affect their capability in facilitating ice nucleation. Via molecular dynamics simulations, here we show that the detailed features of surfaces, such as atomic arrangements, lattice parameters, hydrophobicity, and function forms of surfaces' interaction to water molecules, generally affect the ice nucleation through the average adsorption energy per unit-area surfaces to individual water molecules, when the lattice of surfaces mismatches that of ice. However, for the surfaces whose lattice matches ice, even the detailed function form of the surfaces' interaction to water molecules can largely regulate the icing ability of these surfaces. This study provides new insights into understanding the diverse relationship between various microscopic features of different material surfaces and their nucleation efficacy.

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Variational quantum simulation of thermal statistical states on a superconducting quantum processer Xue-Yi Guo(郭学仪), Shang-Shu Li(李尚书), Xiao Xiao(效骁), Zhong-Cheng Xiang(相忠诚), Zi-Yong Ge(葛自勇), He-Kang Li(李贺康), Peng-Tao Song(宋鹏涛), Yi Peng(彭益), Zhan Wang(王战), Kai Xu(许凯), Pan Zhang(张潘), Lei Wang(王磊), Dong-Ning Zheng(郑东宁), and Heng Fan(范桁) Chin. Phys. B, 2023, 32 (1): 010307.   DOI: 10.1088/1674-1056/aca7f3 Abstract （435）   HTML （8）    PDF （3465KB）（466）       Knowledge map    Quantum computers promise to solve finite-temperature properties of quantum many-body systems, which is generally challenging for classical computers due to high computational complexities. Here, we report experimental preparations of Gibbs states and excited states of Heisenberg $XX$ and $XXZ$ models by using a 5-qubit programmable superconducting processor. In the experiments, we apply a hybrid quantum-classical algorithm to generate finite temperature states with classical probability models and variational quantum circuits. We reveal that the Hamiltonians can be fully diagonalized with optimized quantum circuits, which enable us to prepare excited states at arbitrary energy density. We demonstrate that the approach has a self-verifying feature and can estimate fundamental thermal observables with a small statistical error. Based on numerical results, we further show that the time complexity of our approach scales polynomially in the number of qubits, revealing its potential in solving large-scale problems.

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Superconducting properties of the C15-type Laves phase ZrIr2 with an Ir-based kagome lattice Qing-Song Yang(杨清松), Bin-Bin Ruan(阮彬彬), Meng-Hu Zhou(周孟虎), Ya-Dong Gu(谷亚东), Ming-Wei Ma(马明伟), Gen-Fu Chen(陈根富), and Zhi-An Ren(任治安) Chin. Phys. B, 2023, 32 (1): 017402.   DOI: 10.1088/1674-1056/aca3a2 Abstract （225）   HTML （10）    PDF （2233KB）（231）       Knowledge map    We report systematic studies on superconducting properties of the Laves phase superconductor ZrIr$_2$. It crystallizes in a C15-type (cubic MgCu$_2$-type, space group $Fd\overline{3}m$) structure in which the Ir atoms form a kagome lattice, with cell parameters $a=b=c=7.3596(1)$ Å. Resistivity and magnetic susceptibility measurements indicate that ZrIr$_2$ is a type-II superconductor with a transition temperature of 4.0 K. The estimated lower and upper critical fields are 12.8 mT and 4.78 T, respectively. Heat capacity measurements confirm the bulk superconductivity in ZrIr$_2$. ZrIr$_2$ is found to possibly host strong-coupled s-wave superconductivity with the normalized specific heat change $\Delta C_{\rm e}/\gamma T_{\rm c} \sim 1.86$ and the coupling strength $\Delta_0/k_{\rm B}T_{\rm c} \sim 1.92$. First-principles calculations suggest that ZrIr$_2$ has three-dimensional Fermi surfaces with simple topologies, and the states at Fermi level mainly originate from the Ir-5d and Zr-4d orbitals. Similar to SrIr$_2$ and ThIr$_2$, spin--orbit coupling has dramatic influences on the band structure in ZrIr$_2$.

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Fabrication of honeycomb AuTe monolayer with Dirac nodal line fermions Qin Wang(汪琴), Jie Zhang(张杰), Jierui Huang(黄杰瑞), Jinan Shi(时金安), Shuai Zhang(张帅), Hui Guo(郭辉), Li Huang(黄立), Hong Ding(丁洪), Wu Zhou(周武), Yan-Fang Zhang(张艳芳), Xiao Lin(林晓), Shixuan Du(杜世萱), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2023, 32 (1): 016102.   DOI: 10.1088/1674-1056/aca14a Abstract （216）   HTML （3）    PDF （2193KB）（173）       Knowledge map    Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions (DNLFs). Here, we successfully synthesized a gold telluride (AuTe) monolayer by direct tellurizing an Au(111) substrate. Low energy electron diffraction measurements reveal that it is (2×2) AuTe layer stacked onto (3×3) Au(111) substrate. Moreover, scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure. Scanning transmission electron microscopy reveals that it is a single-atom layer. In addition, first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry, which is validated by angle-resolved photoemission spectra. Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.

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