Chin. Phys. B
Citation Search Quick Search

ISSN 1674-1056 (Print)
CN 11-5639/O4
   » About CPB
   » Editorial Board
   » SCI IF
   » Staff
   » Contact
Browse CPB
   » In Press
   » Current Issue
   » Earlier Issues
   » View by Fields
   » Top Downloaded
   » Sci Top Cited
   » Submit an Article
   » Manuscript Tracking
   » Call for Papers
   » Scope
   » Instruction for Authors
   » Copyright Agreement
   » Templates
   » Author FAQs
   » PACS
   » Review Policy
   » Referee Login
   » Referee FAQs
   » Editor in Chief Login
   » Editor Login
   » Office Login

Giant enhancement of superconductivity in few layers MoTe2 Hot!

Yuan Gan(甘远)1,2, Chang-Woo Cho2, Alei Li(李阿蕾)2, Jian Lyu(吕坚)2, Xu Du(杜序)3, Jin-Sheng Wen(温锦生)1, Li-Yuan Zhang(张立源)2
Chin. Phys. B, 2019, 28 (11): 117401 doi: 10.1088/1674-1056/ab457f
Full Text: [PDF 908 KB] (74) RICH HTML
Show Abstract

Recently, the layered transition metal dichalcogenide 1T' MoTe2 has attracted considerable attention due to its non-saturating magnetoresistance, type-II Weyl semimetal properties, superconductivity, and potential candidate for two-dimensional (2D) topological insulator in the single-and few-layer limit. Here in this work, we perform systematic transport measurements on thin flakes of MoTe2 prepared by mechanical exfoliation. We find that MoTe2 flakes are superconducting and have an onset superconducting transition temperature Tc up to 5.3 K, which significantly exceeds that of its bulk counterpart. The in-plane upper critical field (Hc2||) is much higher than the Pauli paramagnetic limit, implying that the MoTe2 flakes have Zeeman-protected Ising superconductivity. Furthermore, the Tc and Hc2 can be tuned by up to 320 mK and 400 mT by applying a gate voltage. Our result indicates that MoTe2 flake is a good candidate for studying exotic superconductivity with nontrivial topological properties.

Plasmon reflection reveals local electronic properties of natural graphene wrinkles Hot!

Runkun Chen(陈闰堃)1, Cui Yang(杨翠)1, Yuping Jia(贾玉萍)2,3, Liwei Guo(郭丽伟)4,5,6, Jianing Chen(陈佳宁)1,6
Chin. Phys. B, 2019, 28 (11): 117302 doi: 10.1088/1674-1056/ab46a2
Full Text: [PDF 6231 KB] (59) RICH HTML
Show Abstract

We systematically studied surface plasmons reflection by graphene wrinkles with different heights on SiC substrate. Combined with numerical simulation, we found that the geometry corrugation of a few nanometer height wrinkle alone does not causes a reflection of graphene plasmons. Instead, the separated wrinkle from substrate exhibits a nonlinear spatial Fermi energy distribution along the wrinkle, which acts as a heterojunction. Therefor a higher graphene wrinkle induces a stronger damped region when propagating graphene surface plasmons encounter the wrinkle and get reflected.

Disorder induced phase transition in magnetic higher-order topological insulator: A machine learning study Hot!

Zixian Su(苏子贤)1, Yanzhuo Kang(康艳卓)2, Bofeng Zhang(张博峰)1, Zhiqiang Zhang(张智强)1, Hua Jiang(江华)1,3
Chin. Phys. B, 2019, 28 (11): 117301 doi: 10.1088/1674-1056/ab4582
Full Text: [PDF 2314 KB] (24) RICH HTML
Show Abstract
Previous studies presented the phase diagram induced by the disorder existing separately either in the higher-order topological states or in the topological trivial states, respectively. However, the influence of disorder on the system with the coexistence of the higher-order topological states and other traditional topological states has not been investigated. In this paper, we investigate the disorder induced phase transition in the magnetic higher-order topological insulator. By using the convolutional neural network and non-commutative geometry methods, two independent phase diagrams are calculated. With the comparison between these two diagrams, a topological transition from the normal insulator to the Chern insulator is confirmed. Furthermore, the network based on eigenstate wavefunction studies also presents a transition between the higher-order topological insulator and the Chern insulator.

Atom-pair tunneling and quantum phase transition in asymmetry double-well trap in strong-interaction regime Hot!

Ji-Li Liu(刘吉利)1, Jiu-Qing Liang(梁九卿)2
Chin. Phys. B, 2019, 28 (11): 110304 doi: 10.1088/1674-1056/ab44b6
Full Text: [PDF 487 KB] (62) RICH HTML
Show Abstract

The quantum effect of nonlinear co-tunnelling process, which is dependent on atom-pair tunneling and asymmetry of an double-well trap, is studied by using an asymmetrical extended Bose-Hubbard model. Due to the existence of atom-pair tunneling that describes quantum phenomena of ultracold atom-gas clouds in an asymmetrical double-well trap, the asymmetrical extended Bose-Hubbard model is better than the previous Bose-Hubbard model model by comparing with the experimental data cited from the literature. The dependence of dynamics and quantum phase transition on atom-pair tunneling and asymmetry are investigated. Importantly, it shows that the asymmetry of the extended Bose-Hubbard model, corresponding to the bias between double wells, leads to a number of resonance tunneling processes, which tunneling is renamed conditional resonance tunneling, and corrects the atom-number parity effect by controlling the bias between double wells.

Influence of matrigel on the shape and dynamics of cancer cells Hot!

Teng Ye(叶腾), Feng Qiu(邱峰)
Chin. Phys. B, 2019, 28 (10): 108704 doi: 10.1088/1674-1056/ab4275
Full Text: [PDF 1190 KB] (47) RICH HTML
Show Abstract

The interaction between extracellular matrices and cancer cells plays an important role in regulating cancer cell behaviors. In this article, we use matrigel to mimic extracellular matrices and investigate experimentally how matrigel influences the shape and dynamics of breast cancer cells (MDA-MB-231-GFP cells). We find that matrigel facilitates cancer cells' migration and shape deformation. The influences of the matrigel concentration are also reported.

Robust two-gap strong coupling superconductivity associated with low-lying phonon modes in pressurized Nb5Ir3O superconductors Hot!

Bosen Wang(王铂森), Yaoqing Zhang(张尧卿), Shuxiang Xu(徐淑香), Kento Ishigaki, Kazuyuki Matsubayashi, Jin-Guang Cheng(程金光), Hideo Hosono, Yoshiya Uwatoko
Chin. Phys. B, 2019, 28 (10): 107401 doi: 10.1088/1674-1056/ab4047
Full Text: [PDF 3284 KB] (53) RICH HTML
Show Abstract

We report robust superconducting state and gap symmetry of Nb5Ir3O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb5Ir3O is a strongly coupled superconductor with ΔC/γnTc~1.91 and double s-wave superconducting gaps of 2L(0)/kBTc~6.56 and 2S(0)/kBTc~2.36 accounting for 90% and 10%, respectively. The (Cp-γnT)/T3 vs. T plot shows a broad peak at~23 K, indicating phonon softening and the appearance of low-lying phonon mode associated with the interstitial oxygen. This behavior explains the monotonic increase of Tc in Nb5Ir3O(1-δ) by strengthening the electron-phonon coupling and enlarging the density of states at Fermi level. The Hall coefficient is temperature independent below 200 K, and changes its sign from positive to negative above 250 K, suggesting that carrier is across the hole- to electron-dominant regions and the multi-band electronic structures. On warming, the resistivity shows a gradual crossover from T2- to T3-dependence at a critical temperature T*, and a broad peak at a temperature Tp. The reduced Tc under pressure is linearly correlated with lattice parameters c/a ratio and Tp, suggesting the important phonon contributions in Nb5Ir3O as a phonon-medicated superconductor. Possible physical mechanisms are proposed.

Electronic structure of molecular beam epitaxy grown 1T'-MoTe2 film and strain effect Hot!

Xue Zhou(周雪), Zeyu Jiang(姜泽禹), Kenan Zhang(张柯楠), Wei Yao(姚维), Mingzhe Yan(颜明哲), Hongyun Zhang(张红云), Wenhui Duan(段文晖), Shuyun Zhou(周树云)
Chin. Phys. B, 2019, 28 (10): 107307 doi: 10.1088/1674-1056/ab43ba
Full Text: [PDF 1919 KB] (67) RICH HTML
Show Abstract

Atomically thin transition metal dichalcogenide films with distorted trigonal (1T') phase have been predicted to be candidates for realizing quantum spin Hall effect. Growth of 1T' film and experimental investigation of its electronic structure are critical. Here we report the electronic structure of 1T'-MoTe2 films grown by molecular beam epitaxy (MBE). Growth of the 1T'-MoTe2 film depends critically on the substrate temperature, and successful growth of the film is indicated by streaky stripes in the reflection high energy electron diffraction (RHEED) and sharp diffraction spots in the low energy electron diffraction (LEED). Angle-resolved photoemission spectroscopy (ARPES) measurements reveal a metallic behavior in the as-grown film with an overlap between the conduction and valence bands. First principles calculation suggests that a suitable tensile strain along the a-axis direction is needed to induce a gap to make it an insulator. Our work not only reports the electronic structure of MBE grown 1T'-MoTe2 films, but also provides insights for strain engineering to make it possible for quantum spin Hall effect.

Structural and electronic properties of transition-metal chalcogenides Mo5S4 nanowires Hot!

Ming-Shuai Qiu(邱明帅), Huai-Hong Guo(郭怀红), Ye Zhang(张也), Bao-Juan Dong(董宝娟), Sajjad Ali(阿里.萨贾德), Teng Yang(杨腾)
Chin. Phys. B, 2019, 28 (10): 106103 doi: 10.1088/1674-1056/ab3f9a
Full Text: [PDF 3987 KB] (42) RICH HTML
Show Abstract

Transition-metal chalcogenide nanowires (TMCN) as a viable candidate for nanoscale applications have been attracting much attention for the last few decades. Starting from the rigid building block of M6 octahedra (M=transition metal), depending on the way of connection between M6 and decoration by chalcogenide atoms, multiple types of extended TMCN nanowires can be constructed based on some basic rules of backbone construction proposed here. Note that the well-known Chevrel-phase based M6X6 and M6X9 (X=chalcogenide atom) nanowires, which are among our proposed structures, have been successfully synthesized by experiment and well studied. More interestingly, based on the construction principles, we predict three new structural phases (the cap, edge, and C&E phases) of Mo5S4, one of which (the edge phase) has been obtained by top-down electron beam lithography on two-dimensional MoS2, and the C&E phase is yet to be synthesized but appears more stable than the edge phase. The stability of the new phases of Mo5S4 is further substantiated by crystal orbital overlapping population (COOP), phonon dispersion relation, and thermodynamic calculation. The barrier of the structural transition between different phases of Mo5S4 shows that it is very likely to realize an conversion from the experimentally achieved structure to the most stable C&E phase. The calculated electronic structure shows an interesting band nesting between valence and conduction bands of the C&E Mo5S4 phase, suggesting that such a nanowire structure can be well suitable for optoelectronic sensor applications.

Characterize and optimize the four-wave mixing in dual-interferometer coupled silicon microrings Hot!

Chao Wu(吴超), Yingwen Liu(刘英文), Xiaowen Gu(顾晓文), Shichuan Xue(薛诗川), Xinxin Yu(郁鑫鑫), Yuechan Kong(孔月婵), Xiaogang Qiang(强晓刚), Junjie Wu(吴俊杰), Zhihong Zhu(朱志宏), Ping Xu(徐平)
Chin. Phys. B, 2019, 28 (10): 104211 doi: 10.1088/1674-1056/ab3f9b
Full Text: [PDF 1142 KB] (55) RICH HTML
Show Abstract

By designing and fabricating a series of dual-interferometer coupled silicon microrings, the coupling condition of the pump, signal, and idler beams can be engineered independently and then we carried out both the continuous-wave and pulse pumped four-wave mixing experiments to verify the dependence of conversion efficiency on the coupling conditions of the four interacting beams, respectively. Under the continuous-wave pump, the four-wave mixing efficiency gets maximized when both the pump and signal/idler beams are closely operated at the critical coupling point, while for the pulse pump case, the efficiency can be enhanced greatly when the pump and converted idler beams are all overcoupled. These experiment results agree well with our theoretical calculations. Our design provides a platform for explicitly characterizing the four-wave mixing under different pumping conditions, and offers a method to optimize the four-wave mixing, which will facilitate the development of on-chip all-optical signal processing with a higher efficiency or reduced pump power.

Manipulation of superconducting qubit with direct digital synthesis Hot!

Zhi-Yuan Li(李志远), Hai-Feng Yu(于海峰), Xin-Sheng Tan(谭新生), Shi-Ping Zhao(赵士平), Yang Yu(于扬)
Chin. Phys. B, 2019, 28 (9): 098505 doi: 10.1088/1674-1056/ab37f9
Full Text: [PDF 823 KB] (101) RICH HTML
Show Abstract

We investigate the XY control and manipulation of the superconducting qubit state using direct digital synthesis (DDS) for the microwave pulse signal generation. The decoherence time, gate fidelity, and other qubit properties are measured and carefully characterized, and compared with the results obtained by using the traditional mixing technique for the microwave pulse generation. In particular, the qubit performance in the state manipulation with respect to the sampling rate of DDS is studied. Our results demonstrate that the present technique provides a simple and effective method for the XY control and manipulation of the superconducting qubit state. Realistic applications of the technique for the possible future scalable superconducting quantum computation are discussed.

Dipole-dipole interactions enhance non-Markovianity and protect information against dissipation Hot!

Munsif Jan, Xiao-Ye Xu(许小冶), Qin-Qin Wang(王琴琴), Zhe Chen(陈哲), Yong-Jian Han(韩永建), Chuan-Feng Li(李传锋), Guang-Can Guo(郭光灿)
Chin. Phys. B, 2019, 28 (9): 090303 doi: 10.1088/1674-1056/ab37f2
Full Text: [PDF 555 KB] (89) RICH HTML
Show Abstract

Preserving non-Markovianity and quantum entanglement from decoherence effect is of theoretical and practical significance in the quantum information processing technologies. In this context, we study a system S that is initially correlated with an ancilla A, which interacts with the environment E via an amplitude damping channel. We also consider dipole-dipole interactions (DDIs) between the system and ancilla, which are responsible for strong correlations. We investigate the impact of DDIs and detuning on the non-Markovianity and information exchange in different environments. We show that DDIs are not only better than detuning at protecting the information (without destroying the memory effect) but also induce memory by causing a transition from Markovian to non-Markovian dynamics. In contrast, although detuning also protects the information, it causes a transition from non-Markovian to the Markovian dynamics. In addition, we demonstrate that the non-Markovianity grows with increasing DDI strength and diminishes with increasing detuning. We also show that the effects of negative detuning and DDIs can cancel out each other, causing a certain loss of coherence and information.

Attacking a high-dimensional quantum key distribution system with wavelength-dependent beam splitter Hot!

Ge-Hai Du(杜舸海), Hong-Wei Li(李宏伟), Yang Wang(汪洋), Wan-Su Bao(鲍皖苏)
Chin. Phys. B, 2019, 28 (9): 090301 doi: 10.1088/1674-1056/ab343c
Full Text: [PDF 1104 KB] (82) RICH HTML
Show Abstract

The unconditional security of quantum key distribution (QKD) can be guaranteed by the nature of quantum physics. Compared with the traditional two-dimensional BB84 QKD protocol, high-dimensional quantum key distribution (HD-QKD) can be applied to generate much more secret key. Nonetheless, practical imperfections in realistic systems can be exploited by the third party to eavesdrop the secret key. The practical beam splitter has a correlation with wavelength, where different wavelengths have different coupling ratios. Using this property, we propose a wavelength-dependent attack towards time-bin high-dimensional QKD system. What is more, we demonstrate that this attacking protocol can be applied to arbitrary d-dimensional QKD system, and higher-dimensional QKD system is more vulnerable to this attacking strategy.

SymTopo:An automatic tool for calculating topological properties of nonmagnetic crystalline materials Hot!

Yuqing He(贺雨晴), Yi Jiang(蒋毅), Tiantian Zhang(张田田), He Huang(黄荷), Chen Fang(方辰), Zhong Jin(金钟)
Chin. Phys. B, 2019, 28 (8): 087102 doi: 10.1088/1674-1056/28/8/087102
Full Text: [PDF 1222 KB] (168) RICH HTML
Show Abstract

Topological materials have novel properties both in their bulk and boundaries, thereby attracting a wide interest in the theoretical and experimental communities. The recent development of the topological quantum chemistry and symmetry-based indicator theory in this field has significantly simplified the procedure for determining the topological properties of nonmagnetic crystalline materials. Accordingly, a large number of new topological materials have been found by scanning large crystal databases. This study provides details on the algorithm used in the Catalogue of Topological Electronic Materials. Moreover, based on the algorithm, we develop an automatic package named SymTopo, which calculates the symmetry representations of any given nonmagnetic crystalline material and predicts its topological properties. This package may facilitate the discovery of more topological materials in the future.

First-principles study of the band gap tuning and doping control in CdSexTe1-x alloy for high efficiency solar cell Hot!

Jingxiu Yang(杨竞秀), Su-Huai Wei(魏苏淮)
Chin. Phys. B, 2019, 28 (8): 086106 doi: 10.1088/1674-1056/28/8/086106
Full Text: [PDF 526 KB] (114) RICH HTML
Show Abstract

CdTe is one of the leading materials for low cost, high efficiency thin-film solar cells with a nearly ideal band gap of 1.48 eV. However, its solar to electricity power conversion efficiency (PCE) is hindered by the relatively low open circuit voltage (VOC) due to intrinsic defect related issues. Here, we propose that alloying CdTe with CdSe could possibly improve the solar cell performance by reducing the “ideal” band gap of CdTe to gain more short-circuit current from long-wavelength absorption without sacrificing much VOC. Using the hybrid functional calculation, we find that the minimum band gap of the CdTe1-xSex alloy can be reduced from 1.48 eV at x=0 to 1.39 eV at x=0.32, and most of the change come from the lowering of the conduction band minimum. We also show that the formation of the alloy can improve the p-type doping of CuCd impurity based on the reduced effective formation energy and nearly constant effective transition energy level, thus possibly enhance VOC, thus PCE.

Non-Stokes drag coefficient in single-particle electrophoresis:New insights on a classical problem Hot!

Mai-Jia Liao(廖麦嘉), Ming-Tzo Wei(魏名佐), Shi-Xin Xu(徐士鑫), H Daniel Ou-Yang(歐陽新喬), Ping Sheng(沈平)
Chin. Phys. B, 2019, 28 (8): 084701 doi: 10.1088/1674-1056/28/8/084701
Full Text: [PDF 2317 KB] (68) RICH HTML
Show Abstract

We measured the intrinsic electrophoretic drag coefficient of a single charged particle by optically trapping the particle and applying an AC electric field, and found it to be markedly different from that of the Stokes drag. The drag coefficient, along with the measured electrical force, yield a mobility-zeta potential relation that agrees with the literature. By using the measured mobility as input, numerical calculations based on the Poisson-Nernst-Planck equations, coupled to the Navier-Stokes equation, reveal an intriguing microscopic electroosmotic flow near the particle surface, with a well-defined transition between an inner flow field and an outer flow field in the vicinity of electric double layer's outer boundary. This distinctive interface delineates the surface that gives the correct drag coefficient and the effective electric charge. The consistency between experiments and theoretical predictions provides new insights into the classic electrophoresis problem, and can shed light on new applications of electrophoresis to investigate biological nanoparticles.

Evolution of incommensurate superstructure and electronic structure with Pb substitution in (Bi2-xPbx)Sr2CaCu2O8+δ superconductors Hot!

Jing Liu(刘静), Lin Zhao(赵林), Qiang Gao(高强), Ping Ai(艾平), Lu Zhang(张璐), Tao Xie(谢涛), Jian-Wei Huang(黄建伟), Ying Ding(丁颖), Cheng Hu(胡成), Hong-Tao Yan(闫洪涛), Chun-Yao Song(宋春尧), Yu Xu(徐煜), Cong Li(李聪), Yong-Qing Cai(蔡永青), Hong-Tao Rong(戎洪涛), Ding-Song Wu(吴定松), Guo-Dong Liu(刘国东), Qing-Yan Wang(王庆艳), Yuan Huang(黄元), Feng-Feng Zhang(张丰丰), Feng Yang(杨峰), Qin-Jun Peng(彭钦军), Shi-Liang Li(李世亮), Huai-Xin Yang(杨槐馨), Jian-Qi Li(李建奇), Zu-Yan Xu(许祖彦), Xing-Jiang Zhou(周兴江)
Chin. Phys. B, 2019, 28 (7): 077403 doi: 10.1088/1674-1056/28/7/077403
Full Text: [PDF 4430 KB] (214) RICH HTML
Show Abstract

High-quality Bi2-xPbxSr2CaCu2O8+δ (Bi2212) single crystals have been successfully grown by the traveling solvent floating zone technique with a wide range of Pb substitution (x=0-0.8). The samples are characterized by transmission electron microscope (TEM) and measured by high resolution laser-based angle-resolved photoemission spectroscopy (ARPES) with different photon energies. A systematic evolution of the electronic structure and superstructure with Pb substitution has been revealed for the first time. The superstructure shows a significant change with Pb substitution and the incommensurate modulation vector (Q) decreases with increasing Pb substitution. In the meantime, the superstructure intensity from ARPES measurements also decreases dramatically with increasing Pb concentration. The superstructure in Bi2212 can be effectively suppressed by Pb substitution and it nearly disappears with a Pb substitution of x=0.8. We also find that the superstructure bands in ARPES measurements depend sensitively on the photon energy of lasers used; they can become even stronger than the main band when using a laser photon energy of 10.897 eV. These results provide important information on the origin of the incommensurate superstructure and its control and suppression in bismuth-based high temperature superconductors.

A simple rule for finding Dirac cones in bilayered perovskites Hot!

Xuejiao Chen(陈雪娇), Lei Liu(刘雷), Dezhen Shen(申德振)
Chin. Phys. B, 2019, 28 (7): 077106 doi: 10.1088/1674-1056/28/7/077106
Full Text: [PDF 2231 KB] (120) RICH HTML
Show Abstract

A simple rule for finding Dirac cone electronic states in solids is proposed, which is neglecting those lattice atoms inert to particular electronic bands, and pursuing the two-dimensional (2D) graphene-like quasi-atom lattices with s- and p-bindings by considering the equivalent atom groups in the unit cell as quasi-atoms. Taking CsPbBr3 and Cs3Bi2Br9 bilayers as examples, we prove the effectiveness and generality of this rule with the density functional theory (DFT) calculations. We demonstrate that both bilayers have Dirac cones around the Fermi level and reveal that their corresponding Fermi velocities can reach as high as~0.2×106 m/s. This makes these new 2D layered materials very promising in making new ultra-fast ionic electronic devices.

Fabrication of large-scale graphene/2D-germanium heterostructure by intercalation Hot!

Hui Guo(郭辉), Xueyan Wang(王雪艳), De-Liang Bao(包德亮), Hong-Liang Lu(路红亮), Yu-Yang Zhang(张余洋), Geng Li(李更), Ye-Liang Wang(王业亮), Shi-Xuan Du(杜世萱), Hong-Jun Gao(高鸿钧)
Chin. Phys. B, 2019, 28 (7): 078103 doi: 10.1088/1674-1056/28/7/078103
Full Text: [PDF 950 KB] (104) RICH HTML
Show Abstract

We report a large-scale, high-quality heterostructure composed of vertically-stacked graphene and two-dimensional (2D) germanium. The heterostructure is constructed by the intercalation-assisted technique. We first synthesize large-scale, single-crystalline graphene on Ir(111) surface and then intercalate germanium at the interface of graphene and Ir(111). The intercalated germanium forms a well-defined 2D layer with a 2×2 superstructure with respect to Ir(111). Theoretical calculations demonstrate that the 2D germanium has a double-layer structure. Raman characterizations show that the 2D germanium effectively weakens the interaction between graphene and Ir substrate, making graphene more like the intrinsic one. Further experiments of low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy (XPS) confirm the formation of large-scale and high-quality graphene/2D-germanium vertical heterostructure. The integration of graphene with a traditional 2D semiconductor provides a platform to explore new physical phenomena in the future.

Possible nodeless s±-wave superconductivity intwisted bilayer graphene Hot!

Zhe Liu(刘哲), Yu Li(李宇), Yi-Feng Yang(杨义峰)
Chin. Phys. B, 2019, 28 (7): 077103 doi: 10.1088/1674-1056/28/7/077103
Full Text: [PDF 5418 KB] (203) RICH HTML
Show Abstract

The recent discovery of superconductivity in the twisted bilayer graphene has stimulated numerous theoretical proposals concerning its exact gap symmetry. Among them, the d+ id or p+ ip-wave was believed to be the most plausible solution. Here, considering that the superconductivity emerges near a correlated insulating state and may be induced by antiferromagnetic spin fluctuations, we apply the strong-coupling Eliashberg theory with both inter- and intraband quantum critical pairing interactions and discuss the possible gap symmetry in an effective low-energy four-orbital model. Our calculations reveal a nodeless s±-wave as the most probable candidate for the superconducting gap symmetry in the experimentally relevant parameter range. This solution is distinctly different from previous theoretical proposals. It highlights the multi-gap nature of the superconductivity and puts the twisted bilayer graphene in the same class as the iron-pnictide, electron-doped cuprate, and some heavy fermion superconductors.

Global phase diagram of a spin-orbit-coupled Kondo lattice model on the honeycomb lattice Hot!

Xin Li(李欣), Rong Yu(俞榕), Qimiao Si
Chin. Phys. B, 2019, 28 (7): 077102 doi: 10.1088/1674-1056/28/7/077102
Full Text: [PDF 737 KB] (77) RICH HTML
Show Abstract

Motivated by the growing interest in the novel quantum phases in materials with strong electron correlations and spin-orbit coupling, we study the interplay among the spin-orbit coupling, Kondo interaction, and magnetic frustration of a Kondo lattice model on a two-dimensional honeycomb lattice. We calculate the renormalized electronic structure and correlation functions at the saddle point based on a fermionic representation of the spin operators. We find a global phase diagram of the model at half-filling, which contains a variety of phases due to the competing interactions. In addition to a Kondo insulator, there is a topological insulator with valence bond solid correlations in the spin sector, and two antiferromagnetic phases. Due to the competition between the spin-orbit coupling and Kondo interaction, the direction of the magnetic moments in the antiferromagnetic phases can be either within or perpendicular to the lattice plane. The latter antiferromagnetic state is topologically nontrivial for moderate and strong spin-orbit couplings.

Page 1 of 21 409 records
Copyright © the Chinese Physical Society
Address: Institute of Physics, Chinese Academy of Sciences, P. O. Box 603,Beijing 100190 China(100190)
Tel: 010-82649026   Fax: 010-82649027   E-Mail:
Supported by Beijing Magtech Co. Ltd. Tel: 86-010-62662699 E-mail: