The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson ef...The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor junctions.Here we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin polarizations.For the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor interfaces.For the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane polarizations.The symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.展开更多
Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-...Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-dibromochrysene(DBCh),we successfully constructed and characterized the large-area two-dimensional chiral networks on Au(111)and one-dimensional metal-liganded chiral chains on Cu(111)respectively.The reasons and processes of chiral transformation of chiral networks on Au(111)were analyzed.We used scanning tunneling spectroscopy(STS)to analyze the electronic state information of this chiral structure.This work combines scanning tunneling microscopy(STM)with non-contact atomic force microscopy(nc-AFM)techniques to achieve ultra-high-resolution characterization of chiral structures on low-dimensional surfaces,which may be applied to the bond analysis of functional nanofilms.Density functional theory(DFT)was used to simulate the adsorption behavior of the molecular and energy analysis in order to verify the experimental results.展开更多
The understanding and reduction of turbulent transport in magneticconfinement devices is not only an academic task, but also the matter of practical interest, sincehigh confinement is chosen as the regime for ITER and...The understanding and reduction of turbulent transport in magneticconfinement devices is not only an academic task, but also the matter of practical interest, sincehigh confinement is chosen as the regime for ITER and possible future reactors it reduces both thesize and the cost. Since the pioneering work on CCT a lot of work has been devoted to the effect ofelectric field biasing carried out on many tokamaks, which in general leads to a strongly varyingradial electric fields as a function of radius and a resulting sheared E x B flow, giving rise toimproved confinement properties. The issue of plasma flows is utterly fundamental for understandingof tokamaks aimed at the achievement of fusion energy. This appears in the well known neoclassicaltheory as the most accomplished and self-consistent basis for understanding of fusion plasmas. Itpertains to the novel concept of 'zonal flows' emerging from the recent development of gyro-kinetictransport codes. The poloidal and toroidal flows are also crucial for the concept of the electricfield shear suppression of plasma turbulence in tokamaks. Yet, this timely and topical issue hasremained largely unaddressed experimentally because of great difficulties of measuring flows inplasmas. Recently, the team of scientists from all over the world developed innovative configurationof probes yielding the flow velocity locally. This timely and topical diagnostics has beensuccessfully applied on many tokamaks ranging from the huge JET through medium TEXTOR to a smallCASTOR due to the excellent collaboration and coordination between research teams. Results causedlarge interest of fusion community born out by numerous invited talks delivered at the majorinternational meetings.展开更多
The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi_(2)T...The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi_(2)Te_(4).By using low-temperature scanning tunneling microscopy and spectroscopy,we observed a localized bound state around the Mn-Bi antisite defect at the Teterminated surface of the antiferromagnetic topological insulator MnBi_(2)Te_(4).When applying a magnetic field perpendicular to the surface(Bz)from–1.5 to 3.0 T,the bound state shifts linearly to a lower energy with increasing Bz,which is attributed to the Zeeman effect.Remarkably,when applying a large range of Bz from–8.0 to 8.0 T,the magnetic field induced reorientation of surface magnetic moments results in an abrupt jump in the local density of states(LDOS),which is characterized by LDOSchange-ratio■quantitatively.Interestingly,two asymmetric critical field,–2.0 and 4.0 T determined by the two peaks in■are observed,which is consistent with simulated results according to a Mills-model,describing a surface spin flop transition(SSF).Our results provide a new flatform for studying the interplay between magnetic order and topological phases in magnetic topological materials.展开更多
An in teg rated approach combi ning den sity functional theory(DFT)calculati ons and atomic resol utio n sea nning tun neling microscopy(STM)is used to study well-defined iron-doped cobalt oxide nanoislands supported ...An in teg rated approach combi ning den sity functional theory(DFT)calculati ons and atomic resol utio n sea nning tun neling microscopy(STM)is used to study well-defined iron-doped cobalt oxide nanoislands supported on Au(111).The focus is on the structure and distribution of Fe dopants within these nanoislands of CoO as a function of Fe to Co ratio.The DFT and STM results agree strongly and complement each other to allow for a more complete un dersta nding of the dopa nt structure trends on the nano scale.Using Fe as a marker,we first find that the stacki ng seque nee of the moire structure of the host cobalt oxide nano islands can be ide ntified un ambiguously through a combinati on of DFT and STM.Using the distinct con trast of the embedded Fe dopa nt atoms as observed with atom-resolved STM,we find correlatio ns betwee n Fe dopa nt positi on and the CoO/Au(111)moire patter n at varyi ng Fe dopa nt den sities.Formatio n of Fe-dopa nt clusters within the nano islands is investigated in detail through DFT and found to agree with the dopant patter ns observed in STM.We find that the structural effects of Fe dopants throughout the nanoislands with the basal planes and the two types of edges—the oxygen and metal edges—have different nature.Both DFT calculations and STM images show a strong preferenee for Fe dopants to be located directly on or near the oxygen edge of the nanoislands as opposed to being directly on or n ear the metal edge.Take n together,our results illustrate that Fe dopa nt incorporati on and distributi on within CoO nanoislands are highly an isotropic and gover ned by both the moire structure of the basal planes as well as nano-size effects present at the under-coordinated edges of different local geometry and chemistries.展开更多
The phase transition of 2,5-distyrylpyrazine （DSP） adsorbed on Au（111） substrate was studied as a function of the substrate potential in 0.1 M HC104, using an in situ scanning tunneling microscope （STM）. Dependi...The phase transition of 2,5-distyrylpyrazine （DSP） adsorbed on Au（111） substrate was studied as a function of the substrate potential in 0.1 M HC104, using an in situ scanning tunneling microscope （STM）. Depending on the applied electric field, DSP formed three distinctly different, two-dimensionally （2D） ordered, supramolecular nanostructures on the Au（111） surface. In the potential range of 0.55 V 〈 E 〈 0.75 V, the DSP molecules formed a close-packed stripe pattern with the adlayer structure （81 ）. When theptentiawareducedt45V〈E〈.55Varidge-ikepaernbuitfrmdimersubunitswasb- 4 5）. decreasing in the electrode potential to 0.2 V 〈 E 〈 0.45 V caused the served, with the adlayer structure -12 Further fn appearance of a herringbone-like pattern consisting of dimer subunits, with the adlayer structure The potential-induced phase transitions revealed the structure-determining role of substrate-adsorbate coordination and intermolecular interaction in forming the distinct 2D adlayer motifs.展开更多
A systematic study is performed on time-dependent dynamic transport characteristics of a side-coupled double-quantum-impurity system based on the hierarchical equations of motion.It is found that the transport current...A systematic study is performed on time-dependent dynamic transport characteristics of a side-coupled double-quantum-impurity system based on the hierarchical equations of motion.It is found that the transport current behaves like a single quantum dot when the coupling strength is low during tunneling or Coulomb coupling.For the case of only tunneling transition,the dynamic current oscillates due to the temporal coherence of the electron tunneling device.The oscillation frequency of the transport current is related to the step voltage applied by the lead,while temperature T,electron-electron interaction U and the bandwidth W have little influence.The amplitude of the current oscillation exists in positive correlation with W and negative correlation with U.With the increase in coupling t_(12) between impurities,the ground state of the system changes from a Kondo singlet of one impurity to a spin singlet of two impurities.Moreover,lowering the temperature could promote the Kondo effect to intensify the oscillation of the dynamic current.When only the Coulomb transition is coupled,it is found that the two split-off Hubbard peaks move upward and have different interference effects on the Kondo peak at the Fermi surface with the increase in U_(12),from the dynamics point of view.展开更多
Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like str...Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like structure possess exotic electronic structures.Here,we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111)and annealing.Few intrinsic defects are observed and studied by scanning tunneling microscopy,indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary.Then,the monolayer AgTe can serve as the template for the following growth of Te film.Meanwhile,some Te atoms are observed in the form of chains on the top of the bottom Te film.Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.展开更多
The reconstructed structures of Cu（100） surface induced by O2 dissociative adsorption were investigated by low energy electron diffraction and scanning tunneling microscopy. At lower oxygen coverage, it was found th...The reconstructed structures of Cu（100） surface induced by O2 dissociative adsorption were investigated by low energy electron diffraction and scanning tunneling microscopy. At lower oxygen coverage, it was found that two reconstructed structures, i.e. c（2×2）-O and （√2×2√2）R45°-O are coexistent. The domain size of the c（2×2）-O structure decreased with the increasing of O2 exposure. The reconstructed structure at very small coverage was also investigated and a “zigzag” structure was observed at this stage. The “zigzag” structure was identified as boundaries of local c（2×2） domains. It was found that the strip region shows much stronger molecule-substrate interaction than that of oxygen covered regions, making it a proper template for patterned organic films. The sequence of the thermal stability was found as zigzag structure〉c（2×2）〉（√2×2√2）R45°-O.展开更多
By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K...By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1403601).
文摘The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor junctions.Here we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin polarizations.For the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor interfaces.For the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane polarizations.The symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.
基金supported by the National Natural Science Foundation of China(Nos.51861020,61901200 and 12064020)the National Recruitment Program for Young Professionals(No.132310976002)+4 种基金the Yunnan Province Science and Technology Plan Project(No.2019FD041)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB30010000)the Reserve Talents for Yunnan Young and Middle Aged Academic and Technical Leaders(No.2017HB010)the Yunnan Province for Recruiting High-Caliber Technological Talents(No.1097816002)Yunnan Fundamental Research Projects(No.202101AU070043).
文摘Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-dibromochrysene(DBCh),we successfully constructed and characterized the large-area two-dimensional chiral networks on Au(111)and one-dimensional metal-liganded chiral chains on Cu(111)respectively.The reasons and processes of chiral transformation of chiral networks on Au(111)were analyzed.We used scanning tunneling spectroscopy(STS)to analyze the electronic state information of this chiral structure.This work combines scanning tunneling microscopy(STM)with non-contact atomic force microscopy(nc-AFM)techniques to achieve ultra-high-resolution characterization of chiral structures on low-dimensional surfaces,which may be applied to the bond analysis of functional nanofilms.Density functional theory(DFT)was used to simulate the adsorption behavior of the molecular and energy analysis in order to verify the experimental results.
文摘The understanding and reduction of turbulent transport in magneticconfinement devices is not only an academic task, but also the matter of practical interest, sincehigh confinement is chosen as the regime for ITER and possible future reactors it reduces both thesize and the cost. Since the pioneering work on CCT a lot of work has been devoted to the effect ofelectric field biasing carried out on many tokamaks, which in general leads to a strongly varyingradial electric fields as a function of radius and a resulting sheared E x B flow, giving rise toimproved confinement properties. The issue of plasma flows is utterly fundamental for understandingof tokamaks aimed at the achievement of fusion energy. This appears in the well known neoclassicaltheory as the most accomplished and self-consistent basis for understanding of fusion plasmas. Itpertains to the novel concept of 'zonal flows' emerging from the recent development of gyro-kinetictransport codes. The poloidal and toroidal flows are also crucial for the concept of the electricfield shear suppression of plasma turbulence in tokamaks. Yet, this timely and topical issue hasremained largely unaddressed experimentally because of great difficulties of measuring flows inplasmas. Recently, the team of scientists from all over the world developed innovative configurationof probes yielding the flow velocity locally. This timely and topical diagnostics has beensuccessfully applied on many tokamaks ranging from the huge JET through medium TEXTOR to a smallCASTOR due to the excellent collaboration and coordination between research teams. Results causedlarge interest of fusion community born out by numerous invited talks delivered at the majorinternational meetings.
基金This work is supported by the National Natural Science Foundation of China(Nos.61888102 and 52022105)National Key Research and Development Projects of China(Nos.2018YFA0305800 and 2019YFA0308500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB30000000 and XDB28000000)CAS Project for Young Scientists in Basic Research(No.YSBR-003)the University of Chinese Academy of Sciences.
文摘The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi_(2)Te_(4).By using low-temperature scanning tunneling microscopy and spectroscopy,we observed a localized bound state around the Mn-Bi antisite defect at the Teterminated surface of the antiferromagnetic topological insulator MnBi_(2)Te_(4).When applying a magnetic field perpendicular to the surface(Bz)from–1.5 to 3.0 T,the bound state shifts linearly to a lower energy with increasing Bz,which is attributed to the Zeeman effect.Remarkably,when applying a large range of Bz from–8.0 to 8.0 T,the magnetic field induced reorientation of surface magnetic moments results in an abrupt jump in the local density of states(LDOS),which is characterized by LDOSchange-ratio■quantitatively.Interestingly,two asymmetric critical field,–2.0 and 4.0 T determined by the two peaks in■are observed,which is consistent with simulated results according to a Mills-model,describing a surface spin flop transition(SSF).Our results provide a new flatform for studying the interplay between magnetic order and topological phases in magnetic topological materials.
基金A.V.acknowledges the Canadian Institute for Advanced Research(CIFAR)for support through the Bio-inspired Solar Energy Program.J.V.L.and J.R.-F.acknowledge the VILLUM foundation.Z.Z.S.would like to acknowledge financial support from the China Scholarship Council(CSC).L.Z.,T.T.,and A.V.would like to acknowledge the use of the computer time allocation at the National Energy Research Scientific Computing Center(NERSC),a DOE Office of Science User Facility supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231the Extreme Science and Engineering Discovery Environment(XSEDE)supported through National Science Foundation Energy under Award Number CHE160084.
文摘An in teg rated approach combi ning den sity functional theory(DFT)calculati ons and atomic resol utio n sea nning tun neling microscopy(STM)is used to study well-defined iron-doped cobalt oxide nanoislands supported on Au(111).The focus is on the structure and distribution of Fe dopants within these nanoislands of CoO as a function of Fe to Co ratio.The DFT and STM results agree strongly and complement each other to allow for a more complete un dersta nding of the dopa nt structure trends on the nano scale.Using Fe as a marker,we first find that the stacki ng seque nee of the moire structure of the host cobalt oxide nano islands can be ide ntified un ambiguously through a combinati on of DFT and STM.Using the distinct con trast of the embedded Fe dopa nt atoms as observed with atom-resolved STM,we find correlatio ns betwee n Fe dopa nt positi on and the CoO/Au(111)moire patter n at varyi ng Fe dopa nt den sities.Formatio n of Fe-dopa nt clusters within the nano islands is investigated in detail through DFT and found to agree with the dopant patter ns observed in STM.We find that the structural effects of Fe dopants throughout the nanoislands with the basal planes and the two types of edges—the oxygen and metal edges—have different nature.Both DFT calculations and STM images show a strong preferenee for Fe dopants to be located directly on or near the oxygen edge of the nanoislands as opposed to being directly on or n ear the metal edge.Take n together,our results illustrate that Fe dopa nt incorporati on and distributi on within CoO nanoislands are highly an isotropic and gover ned by both the moire structure of the basal planes as well as nano-size effects present at the under-coordinated edges of different local geometry and chemistries.
基金supported by the Chinese Academy of Sciences (KZCX2-YW-QN407)the National 973 Program (2009CB421606)+2 种基金the National Natural Science Foundation of China (51078346, 21177141)Youth Innovation Promotion Association, CASthe Project sponsored by SRF for ROCS, SEM
文摘The phase transition of 2,5-distyrylpyrazine （DSP） adsorbed on Au（111） substrate was studied as a function of the substrate potential in 0.1 M HC104, using an in situ scanning tunneling microscope （STM）. Depending on the applied electric field, DSP formed three distinctly different, two-dimensionally （2D） ordered, supramolecular nanostructures on the Au（111） surface. In the potential range of 0.55 V 〈 E 〈 0.75 V, the DSP molecules formed a close-packed stripe pattern with the adlayer structure （81 ）. When theptentiawareducedt45V〈E〈.55Varidge-ikepaernbuitfrmdimersubunitswasb- 4 5）. decreasing in the electrode potential to 0.2 V 〈 E 〈 0.45 V caused the served, with the adlayer structure -12 Further fn appearance of a herringbone-like pattern consisting of dimer subunits, with the adlayer structure The potential-induced phase transitions revealed the structure-determining role of substrate-adsorbate coordination and intermolecular interaction in forming the distinct 2D adlayer motifs.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11774418 and 11374363)。
文摘A systematic study is performed on time-dependent dynamic transport characteristics of a side-coupled double-quantum-impurity system based on the hierarchical equations of motion.It is found that the transport current behaves like a single quantum dot when the coupling strength is low during tunneling or Coulomb coupling.For the case of only tunneling transition,the dynamic current oscillates due to the temporal coherence of the electron tunneling device.The oscillation frequency of the transport current is related to the step voltage applied by the lead,while temperature T,electron-electron interaction U and the bandwidth W have little influence.The amplitude of the current oscillation exists in positive correlation with W and negative correlation with U.With the increase in coupling t_(12) between impurities,the ground state of the system changes from a Kondo singlet of one impurity to a spin singlet of two impurities.Moreover,lowering the temperature could promote the Kondo effect to intensify the oscillation of the dynamic current.When only the Coulomb transition is coupled,it is found that the two split-off Hubbard peaks move upward and have different interference effects on the Kondo peak at the Fermi surface with the increase in U_(12),from the dynamics point of view.
基金This project was supported by the Ministry of Science and Technology(MOST)of China(No.2016YFA0200700)the National Natural Science Foundation of China(NSFC)(Nos.61674045 and 61911540074)+2 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences(Chinese Academy of Sciences,CAS)(Nos.XDB30000000 and QYZDB-SSW-SYS031)Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Nos.JP16H06327,JP16H06504,JP17H01061,and JP17H010610)Osaka University’s International Joint Research Promotion Program(Nos.J171013014,J171013007,J181013006,and Ja19990011).Z.H.C.was supported by the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(No.21XNLG27).
文摘Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like structure possess exotic electronic structures.Here,we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111)and annealing.Few intrinsic defects are observed and studied by scanning tunneling microscopy,indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary.Then,the monolayer AgTe can serve as the template for the following growth of Te film.Meanwhile,some Te atoms are observed in the form of chains on the top of the bottom Te film.Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.60506019）.
文摘The reconstructed structures of Cu（100） surface induced by O2 dissociative adsorption were investigated by low energy electron diffraction and scanning tunneling microscopy. At lower oxygen coverage, it was found that two reconstructed structures, i.e. c（2×2）-O and （√2×2√2）R45°-O are coexistent. The domain size of the c（2×2）-O structure decreased with the increasing of O2 exposure. The reconstructed structure at very small coverage was also investigated and a “zigzag” structure was observed at this stage. The “zigzag” structure was identified as boundaries of local c（2×2） domains. It was found that the strip region shows much stronger molecule-substrate interaction than that of oxygen covered regions, making it a proper template for patterned organic films. The sequence of the thermal stability was found as zigzag structure〉c（2×2）〉（√2×2√2）R45°-O.
基金financially supported by the National Natural Science Foundation of China(Grants Nos.11790311,92165205,51902152,11874210,and 11774149)the National Key R&D Program of China(Grants No.2021YFA1400403)。
文摘By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.
