Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with hon...Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with honeycomb-like arrays of low-defect hexagonal nanopores by observing room-temperature ferromagnetism and spin-based phenomena arising from the zigzag-pore edges. Here, we apply extremely high electric fields to the ferromagnetic (FM) GNMs using an ionic-liquid gate. A large on/off-ratio for hole current is observed for even small applied ionic-liquid gate voltages (Vig). Observations of the magnetoresistance behavior reveal high carrier densities of ~1013 cm-2 at large Vig values. We find a maximum conductance peak in the high -Vig region and its separation into two peaks upon applying a side-gate (in-plane external) voltage (Vex). It is discussed that localized edge-π band with excess-density electrons induced by Vig and its spin splitting for majority and minority of spins by Vex (half-metallicity model) lead to these phenomena. The results must realize critical-element-free novel spintronic devices.展开更多
We report a tunable transverse magnetoresistance of the planar Hall effect(PHE),up to 48%in the Ni80Fe20/HfO2 heterostructures.This control is achieved by applying a gate voltage with an ionic liquid technique at ultr...We report a tunable transverse magnetoresistance of the planar Hall effect(PHE),up to 48%in the Ni80Fe20/HfO2 heterostructures.This control is achieved by applying a gate voltage with an ionic liquid technique at ultra-low voltage,which exhibits a gate-dependent PHE.Moreover,in the range of 0-V to 1-V gate voltage,transverse magnetoresistance of PHE can be continuously regulated.Ferromagnetic resonance(FMR)also demonstrates the shift of the resonance field at low gate voltage.This provides a new method for the design of the electric field continuous control spintronics device with ultra-low energy consumption.展开更多
Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle...Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.展开更多
Manipulating the superconducting states of high transition temperature(high-Tc)cuprate superconductors in an efficient and reliable way is of great importance for their applications in next-generation electronics.Here...Manipulating the superconducting states of high transition temperature(high-Tc)cuprate superconductors in an efficient and reliable way is of great importance for their applications in next-generation electronics.Here,employing ionic liquid gating,a selective control of volatile and non-volatile superconductivity is achieved in pristine insulating Pr2CuO4±δ(PCO)films,based on two distinct mechanisms.Firstly,with positive electric fields,the film can be reversibly switched between superconducting and non-superconducting states,attributed to the carrier doping effect.Secondly,the film becomes more resistive by applying negative bias voltage up to-4V,but strikingly,a non-volatile superconductivity is achieved once the gate voltage is removed.Such phenomenon represents a distinctive route of manipulating superconductivity in PCO,resulting from the doping healing of oxygen vacancies in copper-oxygen planes as unravelled by high-resolution scanning transmission electron microscope and in situ X-ray diffraction experiments.The effective manipulation of volatile/non-volatile superconductivity in the same parent cuprate brings more functionalities to superconducting electronics,as well as supplies flexible samples for investigating the nature of quantum phase transitions in high-Tcsuperconductors.展开更多
Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based...Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based artificial structures play a crucial role owing to their extreme flexibility and tunability in lattice symmetry,chemical composition,and crystal dimensionality.In this article,we present an overview of the recent progress regarding iridate-based artificial structures.We first explicitly introduce several essential concepts in iridates.Then,we illustrate important findings on representative SrIrO_(3)/SrTiO_(3) superlattices,heterostructures comprised of SrIrO3 and magnetic oxides,and their response to external electric-field stimuli.Finally,we comment on existing problems and promising future directions in this exciting field.展开更多
The discovery of superconducting states in the nickelate thin film with infinite-layer structure has paved a new way for studying unconventional superconductivity.So far,research in this field is still very limited du...The discovery of superconducting states in the nickelate thin film with infinite-layer structure has paved a new way for studying unconventional superconductivity.So far,research in this field is still very limited due to difficulties in sample preparation.Here we report the successful preparation of the superconducting state of Nd_(0.8)Sr_(0.2)NiO_(2)thin film(T_(c)=8.0-11.1 K)and study the stability of such films in the ambient environment,water,and under electrochemical conditions.Our work demonstrates that the superconducting state of Nd_(0.8)Sr_(0.2)NiO_(2)is remarkably stable,which can last for at least 47-day continuous exposure to air at 20°C and 35%relative humidity.We also show that the superconductivity disappears after being immersed in de-ionized water at room temperature for 5 h.Surprisingly,it can also survive under ionic liquid gating conditions with an applied voltage of about 4 V,which is even more stable than conventional perovskite complex oxides.展开更多
Rare-earth nickelates possess intrinsic charge order,orbital order,and electron-lattice coupling,which make them very interesting for applications in oxide-based electronic devices.In this study,we grew NdNiO_(3-δ)(N...Rare-earth nickelates possess intrinsic charge order,orbital order,and electron-lattice coupling,which make them very interesting for applications in oxide-based electronic devices.In this study,we grew NdNiO_(3-δ)(NNO) films with oxygen pressures changing from 27 to 10^(-5) Pa.With decreasing oxygen pressure,the antiferromagnetic state of the NNO film becomes a ferromagnetic state,and the resistance increases significantly.According to combined X-ray absorption spectro scopy and X-ray linear dichroism measurements,the ratio of Ni^(2+)-ions increases with decreasing oxygen-pressure,and the preferred orbital occupation changes from x^(2)-y^(2) to 3 z^(2)-r^(2).In addition,using the ionic-liquid gating method to control the migration of oxygen vacancies,both the magnetic properties and resistance of NNO films can be modulated reversibly.The oxygen vacancy induces a valence in the Ni ions and the orbital occupation changes,which alters the magnetic properties and the electronic transport in these NNO films.This study describes a novel tunable method for electronic devices that use NdNiO_(3-δ) films,and opens new doors for future improvements and functionalities.展开更多
文摘Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with honeycomb-like arrays of low-defect hexagonal nanopores by observing room-temperature ferromagnetism and spin-based phenomena arising from the zigzag-pore edges. Here, we apply extremely high electric fields to the ferromagnetic (FM) GNMs using an ionic-liquid gate. A large on/off-ratio for hole current is observed for even small applied ionic-liquid gate voltages (Vig). Observations of the magnetoresistance behavior reveal high carrier densities of ~1013 cm-2 at large Vig values. We find a maximum conductance peak in the high -Vig region and its separation into two peaks upon applying a side-gate (in-plane external) voltage (Vex). It is discussed that localized edge-π band with excess-density electrons induced by Vig and its spin splitting for majority and minority of spins by Vex (half-metallicity model) lead to these phenomena. The results must realize critical-element-free novel spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51671099 and 11974149)the Open Foundation Project of Jiangsu Key Laboratory of Thin Films(Grant No.KJS1745)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT16R35)the Fundamental Research Funds for the Central Universities,China.
文摘We report a tunable transverse magnetoresistance of the planar Hall effect(PHE),up to 48%in the Ni80Fe20/HfO2 heterostructures.This control is achieved by applying a gate voltage with an ionic liquid technique at ultra-low voltage,which exhibits a gate-dependent PHE.Moreover,in the range of 0-V to 1-V gate voltage,transverse magnetoresistance of PHE can be continuously regulated.Ferromagnetic resonance(FMR)also demonstrates the shift of the resonance field at low gate voltage.This provides a new method for the design of the electric field continuous control spintronics device with ultra-low energy consumption.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62074036,61674038,and 11574302)the Foreign Cooperation Project of Fujian Province,China(Grant No.2023I0005)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(Grant No.KF202108)the National Key Research and Development Program of China(Grant No.2016YFB0402303)the Foundation of Fujian Provincial Department of Industry and Information Technology of China(Grant No.82318075)。
文摘Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.
基金supported by the National Key Basic Research Program of China(2015CB921000,2016YFA0300301,2017YFA0302902,2017YFA0303003 and 2018YFB0704102)the National Natural Science Foundation of China(11674374 and 11834016)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB25000000)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-SLH008 and QYZDY-SSW-SLH001)CAS Interdisciplinary Innovation Teambenefited from the bilateral collaboration F.R.S.-FNRS/NSFC(V4/345-DeM-229)。
文摘Manipulating the superconducting states of high transition temperature(high-Tc)cuprate superconductors in an efficient and reliable way is of great importance for their applications in next-generation electronics.Here,employing ionic liquid gating,a selective control of volatile and non-volatile superconductivity is achieved in pristine insulating Pr2CuO4±δ(PCO)films,based on two distinct mechanisms.Firstly,with positive electric fields,the film can be reversibly switched between superconducting and non-superconducting states,attributed to the carrier doping effect.Secondly,the film becomes more resistive by applying negative bias voltage up to-4V,but strikingly,a non-volatile superconductivity is achieved once the gate voltage is removed.Such phenomenon represents a distinctive route of manipulating superconductivity in PCO,resulting from the doping healing of oxygen vacancies in copper-oxygen planes as unravelled by high-resolution scanning transmission electron microscope and in situ X-ray diffraction experiments.The effective manipulation of volatile/non-volatile superconductivity in the same parent cuprate brings more functionalities to superconducting electronics,as well as supplies flexible samples for investigating the nature of quantum phase transitions in high-Tcsuperconductors.
基金support from the National Natural Science Foundation of China(NSFC)under grant No.51872155 and 52025024the Beijing Nature Science Foundation(Z200007)+4 种基金the Ministry of Science and Technology of China(2021YFE0107900 and 2021YFA1400300)support from the High Magnetic Field Laboratory of Anhui Province(AHHM-FX-2021-03)the NSFC under Grant No.12104460support from the NSFC under Grant No.92163113 and No.52250418support from the National Science Foundation under Grant No.DMR1848269.
文摘Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based artificial structures play a crucial role owing to their extreme flexibility and tunability in lattice symmetry,chemical composition,and crystal dimensionality.In this article,we present an overview of the recent progress regarding iridate-based artificial structures.We first explicitly introduce several essential concepts in iridates.Then,we illustrate important findings on representative SrIrO_(3)/SrTiO_(3) superlattices,heterostructures comprised of SrIrO3 and magnetic oxides,and their response to external electric-field stimuli.Finally,we comment on existing problems and promising future directions in this exciting field.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11774044,52072059,and 11822411).
文摘The discovery of superconducting states in the nickelate thin film with infinite-layer structure has paved a new way for studying unconventional superconductivity.So far,research in this field is still very limited due to difficulties in sample preparation.Here we report the successful preparation of the superconducting state of Nd_(0.8)Sr_(0.2)NiO_(2)thin film(T_(c)=8.0-11.1 K)and study the stability of such films in the ambient environment,water,and under electrochemical conditions.Our work demonstrates that the superconducting state of Nd_(0.8)Sr_(0.2)NiO_(2)is remarkably stable,which can last for at least 47-day continuous exposure to air at 20°C and 35%relative humidity.We also show that the superconductivity disappears after being immersed in de-ionized water at room temperature for 5 h.Surprisingly,it can also survive under ionic liquid gating conditions with an applied voltage of about 4 V,which is even more stable than conventional perovskite complex oxides.
基金Project supported by the National Natural Science Foundation of China(51871137,51901118,61434002)the Graduate Student Innovation Project in Shanxi Province(010903010050)。
文摘Rare-earth nickelates possess intrinsic charge order,orbital order,and electron-lattice coupling,which make them very interesting for applications in oxide-based electronic devices.In this study,we grew NdNiO_(3-δ)(NNO) films with oxygen pressures changing from 27 to 10^(-5) Pa.With decreasing oxygen pressure,the antiferromagnetic state of the NNO film becomes a ferromagnetic state,and the resistance increases significantly.According to combined X-ray absorption spectro scopy and X-ray linear dichroism measurements,the ratio of Ni^(2+)-ions increases with decreasing oxygen-pressure,and the preferred orbital occupation changes from x^(2)-y^(2) to 3 z^(2)-r^(2).In addition,using the ionic-liquid gating method to control the migration of oxygen vacancies,both the magnetic properties and resistance of NNO films can be modulated reversibly.The oxygen vacancy induces a valence in the Ni ions and the orbital occupation changes,which alters the magnetic properties and the electronic transport in these NNO films.This study describes a novel tunable method for electronic devices that use NdNiO_(3-δ) films,and opens new doors for future improvements and functionalities.
