The electronic doping effect on both the superconductivity and the nematic order in the FeSe nanoflake are investigated by using the electric-double-layer transistor configuration. The superconductivity can be effecti...The electronic doping effect on both the superconductivity and the nematic order in the FeSe nanoflake are investigated by using the electric-double-layer transistor configuration. The superconductivity can be effectively controlled by electronic doping, and the onset superconducting transition temperature Tc reaches as high as 45 K at a gate voltage Of Vg = 4 V. Meanwhile, the nematic phase is gradually suppressed with the increase of electronic doping （or Vg）. The results provide an effective method with variable charge doping for investigation of the rich physics in the FeSe superconductor.展开更多
The superconducting state typically favors a uniform spatial distribution akin to ferromagnetism.Nevertheless,the pair-densitywave state exhibits sign changes in the pairing order,leading to potential frustrations in ...The superconducting state typically favors a uniform spatial distribution akin to ferromagnetism.Nevertheless,the pair-densitywave state exhibits sign changes in the pairing order,leading to potential frustrations in phase coherence.We propose a mechanism to the sextetting order stemming from the frustrations in the phase coherence of a pair-density-wave state,whose spatial modulation manifests a vortex-antivortex honeycomb lattice.The classical ground state configurations are mapped to Baxter's three-coloring model,revealing a macroscopic degeneracy accompanied by extensive entropy.The phase coherence problem intertwines the U(1)phases and the vorticity variables.While the resultant color and phase fluctuations suppress the pair-densitywave order,they maintain the sextetting order above the superconducting transition temperature(T_(c)).The 1/3-fractional vortex emerges as the fundamental topological defect in the sextetting order.This novel mechanism of frustrated superconductivity provides an alternative explanation for the experimental observed fractional oscillations in CsV_(3)Sb_(5).展开更多
Superconductivity and magnetism have been interesting topics in condensed mater physics and they have been studied experimentally and theoretically for many years. These two cooperative phenomena are antagonistic unti...Superconductivity and magnetism have been interesting topics in condensed mater physics and they have been studied experimentally and theoretically for many years. These two cooperative phenomena are antagonistic until the discovery of some rare earth ternary compounds that show the coexistence of superconductivity and magnetism. In some of the recently discovered iron-based layered superconductors, superconductivity and magnetism coexist. In the present work we examine the possibility of coexistence of antiferromagnetism and superconductivity in samarium arsenide oxide superconductor (SmAsO1-xFxFe). Using a model of the Hamiltonian and retarded double time Greens function formalism, we found expressions AFM order Parameter (η) and AFM transition temperature (Tm). We obtained the phase diagrams (Tc vs η) and(Tm vs η) to obtain the region where orders, i.e., superconductivity and AFM (antiferromagnetism), coexisted. The region under the intersection of the two merged graphs shows that superconductivity and AFM coexist in the system (SmAsO1-xFxFe).展开更多
We consider a highly unconventional superconducting state with chiral d-wave symmetry in doped graphene under strain with the Gutzwiller–RVB method in the momentum space. It is shown that flat bands emerge in the nor...We consider a highly unconventional superconducting state with chiral d-wave symmetry in doped graphene under strain with the Gutzwiller–RVB method in the momentum space. It is shown that flat bands emerge in the normal state for reasonable strain. As a result, the superconducting critical temperature is found to be linearly proportional to the strength of the electron–electron interaction. Furthermore, the chiral d-wave superconducting state is shown with coexistence of the charge density wave and the pair density wave. There are different coexisting states with those orders under different doping levels.展开更多
It was found that selenium doping can suppress the charge-density-wave（CDW） order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point...It was found that selenium doping can suppress the charge-density-wave（CDW） order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point（QCP） in ZrTe3-xSex near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe（3-x）Sex single crystals（x = 0.044 and 0.051） down to 80 m K. For both samples, the residual linear term κ0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe（3-x）Sex,which indicates conventional superconductivity despite of the existence of a CDW QCP.展开更多
The one-band t–J model captures strong correlations in cuprate high-temperature superconductors.It accounts for the various intertwined spin and charge orders,and the superconductivity in the phase diagrams.To see th...The one-band t–J model captures strong correlations in cuprate high-temperature superconductors.It accounts for the various intertwined spin and charge orders,and the superconductivity in the phase diagrams.To see the correlation effect on the intertwined orders,we implement the density matrix renormalization group method to simulate the t–J model in a small J case with t/J=10,which is in a deeper Mott region than that with t/J?3 in cuprate superconducting compounds.We examine the results on a six-leg lattice with both the nearest and next-nearest-neighbor hoppings and antiferromagnetic coupling,and find the absence of superconductivity and enhanced intertwined spin and charge orders in the phase diagram.Besides the stripe phases,we find a new SDW+CDW phase in which the spin modulation is a(π,π)antiferromagnetism,while the wavelength of the charge modulation is shorter than that of the stripe phases.Our results suggest the enhanced intertwined orders and suppressed superconductivity in the deep Mott region.展开更多
In iron-based superconductors,FeSe has the simplest crystal structure which consists solely of the basic building block,the FeSe layers,that dictates the superconductivity.It undergoes a structural phase transition at...In iron-based superconductors,FeSe has the simplest crystal structure which consists solely of the basic building block,the FeSe layers,that dictates the superconductivity.It undergoes a structural phase transition at around 90 K to enter a nematic state but without a long-range magnetic order.So,FeSe is an ideal system to investigate the nematicity and superconducting mechanism in iron-based superconductors,It represents a unique system that superconductivity and nematicity coexist in the superconducting stale,giving rise to its distinct electronic structure and superconducting gap structure.展开更多
Nematic phase intertwines closely with high-Tc superconductivity in iron-based superconductors.Its mechanism,which is closely related to the pairing mechanism of superconductivity,still remains controversial.Comprehen...Nematic phase intertwines closely with high-Tc superconductivity in iron-based superconductors.Its mechanism,which is closely related to the pairing mechanism of superconductivity,still remains controversial.Comprehensive characterization of the electronic state reconstruction in the nematic phase is thus crucial.However,most experiments focus only on the reconstruction of band dispersions.Another important characteristic of electronic state,the spectral weight,has not been studied in details so far.Here,we studied the spectral weight transfer in the nematic phase of FeSe0.9S0.1 using angle-resolved photoemission spectroscopy and in-situ detwinning technique.There are two elliptical electron pockets overlapping with each other orthogonally at the Brillouin zone corner.We found that,upon cooling,one electron pocket loses spectral weight and fades away,while the other electron pocket gains spectral weight and becomes pronounced.Our results show that the symmetry breaking of the electronic state is manifested by not only the anisotropic band dispersion but also the band-selective modulation of the spectral weight.Our observation completes our understanding of the nematic electronic state,and put strong constraints on the theoretical models.It further provides crucial clues to understand the gap anisotropy and orbital-selective pairing in iron-selenide superconductors.展开更多
In the present theoretical work, superconducting order parameter (∆) and electronic specific heat (C<sub>es</sub>) of SmOFeAs iron pnictide (IP) superconductor has been studied using multiband (M...In the present theoretical work, superconducting order parameter (∆) and electronic specific heat (C<sub>es</sub>) of SmOFeAs iron pnictide (IP) superconductor has been studied using multiband (MB) model of IP superconductors. Attempt has been made to use the MB structure of IP superconductors and expressions for critical temperature (T<sub>c</sub>) and C<sub>es</sub> are obtained, calculations being made for one, two and three bands of SmOFeAs. It has been found that MB results are close to the experimental value of T<sub>c</sub> for this compound. C<sub>es</sub> calculations show jump of 1.5 × 10<sup>-5</sup> eV/atom K, 4 × 10<sup>-5</sup> eV/atom K and 4 × 10<sup>-5</sup> eV/atom K for one, two and three band models respectively. The study brings out the importance of MB structure in IPs, highlighting the fact that increasing the number of bands, increases T<sub>c</sub>. The specific heat jump (∆C) does not correspond to the BCS value, thereby proving that IPs are unconventional in nature.展开更多
金属磁微量能计(Metallic Magnetic Calorimeter,MMC)是一种具有极高能量分辨率的低温光子探测器。它通过顺磁材料磁化率在低温下随温度急剧变化的特性来实现对光子能量的精确测量。金属磁微量能计通常使用超导量子干涉器进行信号读出...金属磁微量能计(Metallic Magnetic Calorimeter,MMC)是一种具有极高能量分辨率的低温光子探测器。它通过顺磁材料磁化率在低温下随温度急剧变化的特性来实现对光子能量的精确测量。金属磁微量能计通常使用超导量子干涉器进行信号读出。研究介绍了一种用于金属磁微量能计信号读出的两级超导量子干涉器电路。初级放大器的设计采用了二阶梯度计构型,测试结果显示该设计方案有效的抑制了环境噪声的干扰。在液氦温度下,两级放大电路在磁通锁定环模式下实现了27400 V/A的跨阻增益,白噪声水平达到11.5 pA/Hz^(1/2)。展开更多
Recently,the coexistence of topology and superconductivity has garnered considerable attention.Specifically,the dimensionality of these materials is crucial for the realization of topological quantum computation.Howev...Recently,the coexistence of topology and superconductivity has garnered considerable attention.Specifically,the dimensionality of these materials is crucial for the realization of topological quantum computation.However,the naturally grown materials,especially with one-dimensional feature that exhibits the coexistence of topology and superconductivity,still face challenges in terms of experimental realization and scalability,which hinders the fundamental research development and the potential to revolutionize quantum computing.Here,we report the first experimental synthesis of quasi-one-dimensional InNbS_(2)nanoribbons that exhibit the coexistence of topological order and superconductivity via a chemical vapor transport method.Especially,the inplane upper critical field of InNbS_(2)nanoribbons exceeds the Pauli paramagnetic limit by more than 2.2 times,which can be attributed to the enhanced spin-orbit coupling and the weakened interlayer interaction between the NbS_(2)layers induced by the insertion of In atoms,making InNbS_(2)exhibit spin-momentum locking similar to that of monolayer NbS_(2).Moreover,for the first time,we report the superconducting diode effect in a quasi-one-dimensional superconductor system without any inherent geometric imperfections.The measured maximum efficiency is manifested as 14%,observed atμ0H≈±60 mT,and we propose that the superconducting diode effect can potentially be attributed to the presence of the nontrivial topological band.Our work provides a platform for studying exotic phenomena in condensed matter physics and potential applications in quantum computing and quantum information processing.展开更多
Many issues concerning the origin of high-temperature superconductivity(HTS)are still under debate.For example,how the magnetic order varies with doping and its relationship with the superconducting temperature(Tc);an...Many issues concerning the origin of high-temperature superconductivity(HTS)are still under debate.For example,how the magnetic order varies with doping and its relationship with the superconducting temperature(Tc);and why Tcalways peaks near the quantum critical point.In this paper,taking hole-doped La_(2)CuO_(4)as a classical example,we employ the first-principles band structure and total energy calculations with Monte Carlo simulations to explore how the symmetry-breaking magnetic ground state evolves with hole doping and the origin of a dome-shaped superconductivity region in the phase diagram.We demonstrate that the local antiferromagnetic order and doping play key roles in determining the electron-phonon coupling,thus Tc.Initially,the La_(2)CuO_(4)possesses a checkerboard local antiferromagnetic ground state.As the hole doping increases,Tcincreases with the enhanced electron-phonon coupling strength.But as the doping increases further,the strength of the antiferromagnetic interaction weakens and spin fluctuation increases.At the critical doping level,a magnetic phase transition occurs that reduces the local antiferromagnetism-assisted electron-phonon coupling,thus diminishing the Tc.The superconductivity disappears in the heavily overdoped region when the ferromagnetic order dominates.These observations could account for why cuprates have a dome-shaped superconductivity region in the phase diagram.Our study,thus,contributes to a fundamental understanding of the correlation between doping,local magnetic order,and superconductivity of HTS.展开更多
针对脉宽调制电流源型换流器(pulse-width modulated current source converter,PWM-CSC)的超导磁储能(superconducting magnetic energy storage,SMES)系统,设计了一款自适应分数阶滑模控制(adaptive fractional-order sliding-mode co...针对脉宽调制电流源型换流器(pulse-width modulated current source converter,PWM-CSC)的超导磁储能(superconducting magnetic energy storage,SMES)系统,设计了一款自适应分数阶滑模控制(adaptive fractional-order sliding-mode control,AFOSMC)策略。首先,将SMES系统的非线性、参数不确定性、未建模动态、以及外部扰动聚合成一个广义扰动,并利用滑模状态扰动观测器(sliding-mode state and perturbation observer,SMSPO)在线估计该扰动值。随后,通过分数阶滑模控制(fractional-order sliding-mode control,FOSMC)实时地对该扰动进行完全补偿,从而显著提高SMES系统的鲁棒性并获得全局一致的控制性能。同时,AFOSMC仅需测量SMES系统的d-q轴电流,并且采用扰动的实时估计值替代上限值进行补偿,因而其易于实现且具有更为合理的控制成本。该文进行了4种算例研究,即:1)有功功率和无功功率调节;2)电网故障下的系统恢复;3)新能源接入的功率波动平抑;4)参数不确定时的鲁棒性。仿真结果表明,AFOSMC相较于其他算法,具有最强的鲁棒性和最佳的动态响应性能。最后,基于dSpace的硬件在环(hardware-in-loop,HIL)实验验证了其硬件可行性。展开更多
超导HEB(Hot Electron Bolometer)热电子混频器是1THz以上灵敏度最高的相干探测器,为了进一步提高其灵敏度,有效减小射频信号在传输路径中的损耗,实现超导HEB混频器的超宽带混频功能,设计高耦合效率的射频匹配电路尤为重要。首先提出了...超导HEB(Hot Electron Bolometer)热电子混频器是1THz以上灵敏度最高的相干探测器,为了进一步提高其灵敏度,有效减小射频信号在传输路径中的损耗,实现超导HEB混频器的超宽带混频功能,设计高耦合效率的射频匹配电路尤为重要。首先提出了混频器耦合电路的理论模型,然后采用三维电磁场仿真软件HFSS和类似于准光学天线的集总源法,设计了一种超宽带、低损耗的太赫兹信号耦合电路,对超导HEB混频器的嵌入阻抗在整个0.9～1.3THz的工作频带范围内进行了详细的分析。系统研究了低通滤波器中高低阻抗线结构,波导到微带转换中存在的高次模对射频信号传输的影响,并模拟仿真了实验中可能出现的磨片厚度误差对嵌入阻抗的影响。分析结果表明,该混频器的嵌入阻抗为35Ω-j10Ω左右,在整个工作频带内变化缓慢,能够实现超宽频带匹配,混频器的相对工作带宽可达到36%,仿真结果和理论模型计算结果完全一致。该研究结果对研制超宽带高灵敏度的超导HEB混频器具有很好的指导意义。展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11174294,11174291,11374302,11304319,U1332209,U1432251 and U1532153the China Postdoctoral Science Foundation under Grant No 2015M582020+1 种基金the Program of Users with Excellence,the Hefei Science Center of Chinese Academy of Sciencesthe CAS/SAFEA International Partnership Program for Creative Research Teams of China
文摘The electronic doping effect on both the superconductivity and the nematic order in the FeSe nanoflake are investigated by using the electric-double-layer transistor configuration. The superconductivity can be effectively controlled by electronic doping, and the onset superconducting transition temperature Tc reaches as high as 45 K at a gate voltage Of Vg = 4 V. Meanwhile, the nematic phase is gradually suppressed with the increase of electronic doping （or Vg）. The results provide an effective method with variable charge doping for investigation of the rich physics in the FeSe superconductor.
基金supported by the National Natural Science Foundation of China(Grant Nos.12234016 and 12174317)supported by the National Natural Science Foundation of China(Grant No.12074031)+1 种基金supported by the National Natural Science Foundation of China(Grant No.12304180)supported by the New Cornerstone Science Foundation。
文摘The superconducting state typically favors a uniform spatial distribution akin to ferromagnetism.Nevertheless,the pair-densitywave state exhibits sign changes in the pairing order,leading to potential frustrations in phase coherence.We propose a mechanism to the sextetting order stemming from the frustrations in the phase coherence of a pair-density-wave state,whose spatial modulation manifests a vortex-antivortex honeycomb lattice.The classical ground state configurations are mapped to Baxter's three-coloring model,revealing a macroscopic degeneracy accompanied by extensive entropy.The phase coherence problem intertwines the U(1)phases and the vorticity variables.While the resultant color and phase fluctuations suppress the pair-densitywave order,they maintain the sextetting order above the superconducting transition temperature(T_(c)).The 1/3-fractional vortex emerges as the fundamental topological defect in the sextetting order.This novel mechanism of frustrated superconductivity provides an alternative explanation for the experimental observed fractional oscillations in CsV_(3)Sb_(5).
文摘Superconductivity and magnetism have been interesting topics in condensed mater physics and they have been studied experimentally and theoretically for many years. These two cooperative phenomena are antagonistic until the discovery of some rare earth ternary compounds that show the coexistence of superconductivity and magnetism. In some of the recently discovered iron-based layered superconductors, superconductivity and magnetism coexist. In the present work we examine the possibility of coexistence of antiferromagnetism and superconductivity in samarium arsenide oxide superconductor (SmAsO1-xFxFe). Using a model of the Hamiltonian and retarded double time Greens function formalism, we found expressions AFM order Parameter (η) and AFM transition temperature (Tm). We obtained the phase diagrams (Tc vs η) and(Tm vs η) to obtain the region where orders, i.e., superconductivity and AFM (antiferromagnetism), coexisted. The region under the intersection of the two merged graphs shows that superconductivity and AFM coexist in the system (SmAsO1-xFxFe).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804213 and 11605109)
文摘We consider a highly unconventional superconducting state with chiral d-wave symmetry in doped graphene under strain with the Gutzwiller–RVB method in the momentum space. It is shown that flat bands emerge in the normal state for reasonable strain. As a result, the superconducting critical temperature is found to be linearly proportional to the strength of the electron–electron interaction. Furthermore, the chiral d-wave superconducting state is shown with coexistence of the charge density wave and the pair density wave. There are different coexisting states with those orders under different doping levels.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB821402 and 2015CB921401)the National Natural Science Foundation of China(Grant Nos.91421101,11422429,and 11204312)+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,China,STCSM of China(Grant No.15XD1500200)Work at Brookhaven National Laboratory was supported by the US DOE under Contract No.DESC00112704
文摘It was found that selenium doping can suppress the charge-density-wave（CDW） order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point（QCP） in ZrTe3-xSex near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe（3-x）Sex single crystals（x = 0.044 and 0.051） down to 80 m K. For both samples, the residual linear term κ0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe（3-x）Sex,which indicates conventional superconductivity despite of the existence of a CDW QCP.
基金the National Key R&D Program of China(Grant No.2022YFA1403700)the National Natural Science Foundation of China(Grant No.12141402)+2 种基金the Science,Technology and Innovation Commission of Shenzhen Municipality(Grant No.ZDSYS20190902092905285)Guangdong Basic and Applied Basic Research Foundation(Grant No.2020B1515120100)Center for Computational Science and Engineering at Southern University of Science and Technology。
文摘The one-band t–J model captures strong correlations in cuprate high-temperature superconductors.It accounts for the various intertwined spin and charge orders,and the superconductivity in the phase diagrams.To see the correlation effect on the intertwined orders,we implement the density matrix renormalization group method to simulate the t–J model in a small J case with t/J=10,which is in a deeper Mott region than that with t/J?3 in cuprate superconducting compounds.We examine the results on a six-leg lattice with both the nearest and next-nearest-neighbor hoppings and antiferromagnetic coupling,and find the absence of superconductivity and enhanced intertwined spin and charge orders in the phase diagram.Besides the stripe phases,we find a new SDW+CDW phase in which the spin modulation is a(π,π)antiferromagnetism,while the wavelength of the charge modulation is shorter than that of the stripe phases.Our results suggest the enhanced intertwined orders and suppressed superconductivity in the deep Mott region.
文摘In iron-based superconductors,FeSe has the simplest crystal structure which consists solely of the basic building block,the FeSe layers,that dictates the superconductivity.It undergoes a structural phase transition at around 90 K to enter a nematic state but without a long-range magnetic order.So,FeSe is an ideal system to investigate the nematicity and superconducting mechanism in iron-based superconductors,It represents a unique system that superconductivity and nematicity coexist in the superconducting stale,giving rise to its distinct electronic structure and superconducting gap structure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11888101,91421107,and 11574004)the National Key Research and Development Program of China(Grant Nos.2016YFA0301003 and 2018YFA0305602).
文摘Nematic phase intertwines closely with high-Tc superconductivity in iron-based superconductors.Its mechanism,which is closely related to the pairing mechanism of superconductivity,still remains controversial.Comprehensive characterization of the electronic state reconstruction in the nematic phase is thus crucial.However,most experiments focus only on the reconstruction of band dispersions.Another important characteristic of electronic state,the spectral weight,has not been studied in details so far.Here,we studied the spectral weight transfer in the nematic phase of FeSe0.9S0.1 using angle-resolved photoemission spectroscopy and in-situ detwinning technique.There are two elliptical electron pockets overlapping with each other orthogonally at the Brillouin zone corner.We found that,upon cooling,one electron pocket loses spectral weight and fades away,while the other electron pocket gains spectral weight and becomes pronounced.Our results show that the symmetry breaking of the electronic state is manifested by not only the anisotropic band dispersion but also the band-selective modulation of the spectral weight.Our observation completes our understanding of the nematic electronic state,and put strong constraints on the theoretical models.It further provides crucial clues to understand the gap anisotropy and orbital-selective pairing in iron-selenide superconductors.
文摘In the present theoretical work, superconducting order parameter (∆) and electronic specific heat (C<sub>es</sub>) of SmOFeAs iron pnictide (IP) superconductor has been studied using multiband (MB) model of IP superconductors. Attempt has been made to use the MB structure of IP superconductors and expressions for critical temperature (T<sub>c</sub>) and C<sub>es</sub> are obtained, calculations being made for one, two and three bands of SmOFeAs. It has been found that MB results are close to the experimental value of T<sub>c</sub> for this compound. C<sub>es</sub> calculations show jump of 1.5 × 10<sup>-5</sup> eV/atom K, 4 × 10<sup>-5</sup> eV/atom K and 4 × 10<sup>-5</sup> eV/atom K for one, two and three band models respectively. The study brings out the importance of MB structure in IPs, highlighting the fact that increasing the number of bands, increases T<sub>c</sub>. The specific heat jump (∆C) does not correspond to the BCS value, thereby proving that IPs are unconventional in nature.
文摘金属磁微量能计(Metallic Magnetic Calorimeter,MMC)是一种具有极高能量分辨率的低温光子探测器。它通过顺磁材料磁化率在低温下随温度急剧变化的特性来实现对光子能量的精确测量。金属磁微量能计通常使用超导量子干涉器进行信号读出。研究介绍了一种用于金属磁微量能计信号读出的两级超导量子干涉器电路。初级放大器的设计采用了二阶梯度计构型,测试结果显示该设计方案有效的抑制了环境噪声的干扰。在液氦温度下,两级放大电路在磁通锁定环模式下实现了27400 V/A的跨阻增益,白噪声水平达到11.5 pA/Hz^(1/2)。
基金supported by Innovation Program for Quantum Science and Technology(No.2021ZD0302800)the National Natural Science Foundation of China(Nos.52373309 and 12374177)+1 种基金University of Macao Start-up research grant(No.SRG2023-00057-IAPME)National Synchrotron Radiation Laboratory(No.KY2060000177).
文摘Recently,the coexistence of topology and superconductivity has garnered considerable attention.Specifically,the dimensionality of these materials is crucial for the realization of topological quantum computation.However,the naturally grown materials,especially with one-dimensional feature that exhibits the coexistence of topology and superconductivity,still face challenges in terms of experimental realization and scalability,which hinders the fundamental research development and the potential to revolutionize quantum computing.Here,we report the first experimental synthesis of quasi-one-dimensional InNbS_(2)nanoribbons that exhibit the coexistence of topological order and superconductivity via a chemical vapor transport method.Especially,the inplane upper critical field of InNbS_(2)nanoribbons exceeds the Pauli paramagnetic limit by more than 2.2 times,which can be attributed to the enhanced spin-orbit coupling and the weakened interlayer interaction between the NbS_(2)layers induced by the insertion of In atoms,making InNbS_(2)exhibit spin-momentum locking similar to that of monolayer NbS_(2).Moreover,for the first time,we report the superconducting diode effect in a quasi-one-dimensional superconductor system without any inherent geometric imperfections.The measured maximum efficiency is manifested as 14%,observed atμ0H≈±60 mT,and we propose that the superconducting diode effect can potentially be attributed to the presence of the nontrivial topological band.Our work provides a platform for studying exotic phenomena in condensed matter physics and potential applications in quantum computing and quantum information processing.
基金supported by the National Natural Science Foundation of China(Grant Nos.61922077,11874347,11991060,12088101,61927901U2230402)+3 种基金the National Key Research and Development Program of China(Grant Nos.2018YFB2200100,and 2020YFB1506400)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0460000)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-026)supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y2021042)。
文摘Many issues concerning the origin of high-temperature superconductivity(HTS)are still under debate.For example,how the magnetic order varies with doping and its relationship with the superconducting temperature(Tc);and why Tcalways peaks near the quantum critical point.In this paper,taking hole-doped La_(2)CuO_(4)as a classical example,we employ the first-principles band structure and total energy calculations with Monte Carlo simulations to explore how the symmetry-breaking magnetic ground state evolves with hole doping and the origin of a dome-shaped superconductivity region in the phase diagram.We demonstrate that the local antiferromagnetic order and doping play key roles in determining the electron-phonon coupling,thus Tc.Initially,the La_(2)CuO_(4)possesses a checkerboard local antiferromagnetic ground state.As the hole doping increases,Tcincreases with the enhanced electron-phonon coupling strength.But as the doping increases further,the strength of the antiferromagnetic interaction weakens and spin fluctuation increases.At the critical doping level,a magnetic phase transition occurs that reduces the local antiferromagnetism-assisted electron-phonon coupling,thus diminishing the Tc.The superconductivity disappears in the heavily overdoped region when the ferromagnetic order dominates.These observations could account for why cuprates have a dome-shaped superconductivity region in the phase diagram.Our study,thus,contributes to a fundamental understanding of the correlation between doping,local magnetic order,and superconductivity of HTS.
文摘针对脉宽调制电流源型换流器(pulse-width modulated current source converter,PWM-CSC)的超导磁储能(superconducting magnetic energy storage,SMES)系统,设计了一款自适应分数阶滑模控制(adaptive fractional-order sliding-mode control,AFOSMC)策略。首先,将SMES系统的非线性、参数不确定性、未建模动态、以及外部扰动聚合成一个广义扰动,并利用滑模状态扰动观测器(sliding-mode state and perturbation observer,SMSPO)在线估计该扰动值。随后,通过分数阶滑模控制(fractional-order sliding-mode control,FOSMC)实时地对该扰动进行完全补偿,从而显著提高SMES系统的鲁棒性并获得全局一致的控制性能。同时,AFOSMC仅需测量SMES系统的d-q轴电流,并且采用扰动的实时估计值替代上限值进行补偿,因而其易于实现且具有更为合理的控制成本。该文进行了4种算例研究,即:1)有功功率和无功功率调节;2)电网故障下的系统恢复;3)新能源接入的功率波动平抑;4)参数不确定时的鲁棒性。仿真结果表明,AFOSMC相较于其他算法,具有最强的鲁棒性和最佳的动态响应性能。最后,基于dSpace的硬件在环(hardware-in-loop,HIL)实验验证了其硬件可行性。
文摘超导HEB(Hot Electron Bolometer)热电子混频器是1THz以上灵敏度最高的相干探测器,为了进一步提高其灵敏度,有效减小射频信号在传输路径中的损耗,实现超导HEB混频器的超宽带混频功能,设计高耦合效率的射频匹配电路尤为重要。首先提出了混频器耦合电路的理论模型,然后采用三维电磁场仿真软件HFSS和类似于准光学天线的集总源法,设计了一种超宽带、低损耗的太赫兹信号耦合电路,对超导HEB混频器的嵌入阻抗在整个0.9～1.3THz的工作频带范围内进行了详细的分析。系统研究了低通滤波器中高低阻抗线结构,波导到微带转换中存在的高次模对射频信号传输的影响,并模拟仿真了实验中可能出现的磨片厚度误差对嵌入阻抗的影响。分析结果表明,该混频器的嵌入阻抗为35Ω-j10Ω左右,在整个工作频带内变化缓慢,能够实现超宽频带匹配,混频器的相对工作带宽可达到36%,仿真结果和理论模型计算结果完全一致。该研究结果对研制超宽带高灵敏度的超导HEB混频器具有很好的指导意义。
