Manipulating emergent quantum phenomena is a key issue for understanding the underlying physics and contributing to possible applications.Here we study the evolution of insulating ground states of Ta_(2)Pu_(3)Te_(5) a...Manipulating emergent quantum phenomena is a key issue for understanding the underlying physics and contributing to possible applications.Here we study the evolution of insulating ground states of Ta_(2)Pu_(3)Te_(5) and Ta_(2)Ni_(3)Te_(5) under in-situ surface potassium deposition via angle-resolved photoemission spectroscopy.Our results confirm the excitonic insulator character of Ta_(2)d_(3)Te_(5).Upon surface doping,the size of its global gap decreases obviously.After a deposition time of more than 7 min,the potassium atoms induce a metal-insulator phase transition and make the system recover to a normal state.In contrast,our results show that the isostructural compound Ta_(2)Ni_(3)Te_(5) is a conventional insulator.The size of its global gap decreases upon surface doping,but persists positive throughout the doping process.Our results not only confirm the excitonic origin of the band gap in Ta_(2)Pd_(3)Te_(5),but also offer an effective method for designing functional quantum devices in the future.展开更多
It is becoming increasingly clear that the exotic properties displayed by correlated electronic materials such as high- Tc superconductivity in cuprates, colossal magnetoresistance （CMR） in manganites, and heavy-fer...It is becoming increasingly clear that the exotic properties displayed by correlated electronic materials such as high- Tc superconductivity in cuprates, colossal magnetoresistance （CMR） in manganites, and heavy-fermion compounds are intimately related to the coexistence of competing nearly degenerate states which couple simultaneously active degrees of freedom---charge, lattice, orbital, and spin states. The striking phenomena associated with these materials are due in a large part to spatial electronic inhomogeneities, or electronic phase separation （EPS）. In many of these hard materials, the functionality is a result of the soft electronic component that leads to self-organization. In this paper, we review our recent work on a novel spatial confinement technique that has led to some fascinating new discoveries about the role of EPS in manganites. Using lithographic techniques to confine manganite thin films to length scales of the EPS domains that reside within them, it is possible to simultaneously probe EPS domains with different electronic states. This method allows for a much more complete view of the phases residing in a material and gives vital information on phase formation, movement, and fluctuation. Pushing this trend to its limit, we propose to control the formation process of the EPS using external local fields, which include magnetic exchange field, strain field, and electric field. We term the ability to pattern EPS ＂electronic nanofabrication.＂ This method allows us to control the global physical properties of the system at a very fundamental level, and greatly enhances the potential for realizing true oxide electronics.展开更多
Micro-patterning is considered to be a promising way to analyze phase-separated manganites. We investigate resistance in micro-patterned La0.325Pr0.3Ca0.375MnO3 wires with width of 10 μm, which is comparable to the p...Micro-patterning is considered to be a promising way to analyze phase-separated manganites. We investigate resistance in micro-patterned La0.325Pr0.3Ca0.375MnO3 wires with width of 10 μm, which is comparable to the phase separation scale in this material. A reentrant of insulating state at the metal-insulator temperature Tp is observed and a giant resistance change of over 90% driven by electric field is achieved by suppression of this insulating state. This resistance change is mostly reversible, The I-V characteristics are measured in order to analyze the origin of the giant electroresistance and two possible explanations are proposed.展开更多
The physical properties of most 2D materials are highly dependent on the nature of their interlayer interaction.In-depth studies of the interlayer interaction are beneficial to the understanding of the physical proper...The physical properties of most 2D materials are highly dependent on the nature of their interlayer interaction.In-depth studies of the interlayer interaction are beneficial to the understanding of the physical properties of 2D materials and permit the development of related devices.Layered magnetic NiPS_(3)has unique magnetic and electronic properties.The electronic band structure and corresponding magnetic state of NiPS_(3)are expected to be sensitive to the interlayer interaction,which can be tuned by external pressure.Here,we report an insulator-metal transition accompanied by the collapse of magnetic order during the 2D-3D structural crossover induced by hydrostatic pressure.A two-stage phase transition from a monoclinic(C2/m)to a trigonal(P31m)lattice is identified via ab initio simulations and confirmed via high-pressure X-ray diffraction and Raman scattering;this transition corresponds to a layer-by-layer slip mechanism along the a-axis.Temperature-dependent resistance measurements and room temperature infrared spectroscopy under different pressures demonstrate that the insulator-metal transition and the collapse of the magnetic order occur at~20 GPa,which is confirmed by low-temperature Raman scattering measurements and theoretical calculations.These results establish a strong correlation between the structural change,electric transport,and magnetic phase transition and expand our understanding of layered magnetic materials.Moreover,the structural transition caused by the interlayer displacement has significance for designing similar devices at ambient pressure.展开更多
The quantum limit, where only the lowest Landau level is occupied by electrons, can be achieved under a high magnetic field when the Landau level splitting is comparable with the Fermi energy. The rather small Fermi p...The quantum limit, where only the lowest Landau level is occupied by electrons, can be achieved under a high magnetic field when the Landau level splitting is comparable with the Fermi energy. The rather small Fermi pockets and Fermi energy in CaFeAsF reported recently make this compound a good candidate for investigating the electrical transport near the quantum limit.Here, we report high-field experiments up to 65 T on a single-crystalline CaFeAsF, which shows a metal-insulator quantum phase transition tuned by the out-of-plane magnetic field. The obtained critical exponent zν through the finite-size scaling analysis is very close to 4/3. This transition is closely associated with the evolution of electronic states approaching the quantum limit.The resistivity behaviors as a function of field and temperature were evaluated based on Adams-Holstein theory(A-H theory).Moreover, the in-plane component of the field, which does not affect the transport behavior in the classical region, suppressed the magnetoresistance near the quantum limit.展开更多
基金Project supported by the Ministry of Science and Technology of China (Grant No. 2022YFA1403800)the National Natural Science Foundation of China (Grant Nos. U2032204,12188101, and U22A6005)+2 种基金the Chinese Academy of Sciences (Grant No. XDB33000000)the Synergetic Extreme Condition User Facility (SECUF)the Center for Materials Genome。
文摘Manipulating emergent quantum phenomena is a key issue for understanding the underlying physics and contributing to possible applications.Here we study the evolution of insulating ground states of Ta_(2)Pu_(3)Te_(5) and Ta_(2)Ni_(3)Te_(5) under in-situ surface potassium deposition via angle-resolved photoemission spectroscopy.Our results confirm the excitonic insulator character of Ta_(2)d_(3)Te_(5).Upon surface doping,the size of its global gap decreases obviously.After a deposition time of more than 7 min,the potassium atoms induce a metal-insulator phase transition and make the system recover to a normal state.In contrast,our results show that the isostructural compound Ta_(2)Ni_(3)Te_(5) is a conventional insulator.The size of its global gap decreases upon surface doping,but persists positive throughout the doping process.Our results not only confirm the excitonic origin of the band gap in Ta_(2)Pd_(3)Te_(5),but also offer an effective method for designing functional quantum devices in the future.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB921801)the National Natural Science Foundation of China(Grant Nos.91121002and11274071)+1 种基金US DOE Office of Basic Energy Sciences,Scientific User Facilities Division,and the US DOE grant DE-SC0002136the US DOE Office of Basic Energy Sciences,Materials Sciences and Engineering Division,through the Oak Ridge National Laboratory
文摘It is becoming increasingly clear that the exotic properties displayed by correlated electronic materials such as high- Tc superconductivity in cuprates, colossal magnetoresistance （CMR） in manganites, and heavy-fermion compounds are intimately related to the coexistence of competing nearly degenerate states which couple simultaneously active degrees of freedom---charge, lattice, orbital, and spin states. The striking phenomena associated with these materials are due in a large part to spatial electronic inhomogeneities, or electronic phase separation （EPS）. In many of these hard materials, the functionality is a result of the soft electronic component that leads to self-organization. In this paper, we review our recent work on a novel spatial confinement technique that has led to some fascinating new discoveries about the role of EPS in manganites. Using lithographic techniques to confine manganite thin films to length scales of the EPS domains that reside within them, it is possible to simultaneously probe EPS domains with different electronic states. This method allows for a much more complete view of the phases residing in a material and gives vital information on phase formation, movement, and fluctuation. Pushing this trend to its limit, we propose to control the formation process of the EPS using external local fields, which include magnetic exchange field, strain field, and electric field. We term the ability to pattern EPS ＂electronic nanofabrication.＂ This method allows us to control the global physical properties of the system at a very fundamental level, and greatly enhances the potential for realizing true oxide electronics.
基金supported by the National Basic Research Program of China(Grant Nos.2011CBA00106 and 2014CB921401)the National Natural Science Foundation of China(Grant Nos.11174342,91321208,and 11374344)
文摘Micro-patterning is considered to be a promising way to analyze phase-separated manganites. We investigate resistance in micro-patterned La0.325Pr0.3Ca0.375MnO3 wires with width of 10 μm, which is comparable to the phase separation scale in this material. A reentrant of insulating state at the metal-insulator temperature Tp is observed and a giant resistance change of over 90% driven by electric field is achieved by suppression of this insulating state. This resistance change is mostly reversible, The I-V characteristics are measured in order to analyze the origin of the giant electroresistance and two possible explanations are proposed.
文摘采用磁控溅射法在STO(001)基片上沉积钙钛矿结构LCMO薄膜,研究了退火温度对LCMO薄膜微结构及电输运特性的影响.研究结果表明,随退火温度的升高,薄膜中氧含量及Mn4+/Mn3+比逐渐升高,LCMO薄膜中的Mn4+/Mn3+比与薄膜中的氧含量有关,当氧含量增大时,Mn4+/Mn3+比相应增大.LCMO薄膜的电阻率随退火温度升高而逐渐减小,而LCMO薄膜的金属-绝缘相变温度随退火温度升高而逐渐升高,经850℃退火处理的LCMO薄膜的金属-绝缘相变温度可达257 K.
基金the National Key Research and Development Program of China(Grant Nos.2016YFA0401503,2018YFA0305700,2017YFA0302904,2020YFA0711502,and 2016YFA0300500)the National Natural Science Foundation of China(Grant Nos.11575288,11974387,U1932215,U1930401,12004014,22090041,and 11774419)+3 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.XDB33000000,XDB25000000,and QYZDBSSW-SLH013)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y202003)the CAS Interdisciplinary Innovation Team(Grant No.JCTD-2019-01)ADXRD measurements were performed at 4W2 High Pressure Station,Beijing Synchrotron Radiation Facility(BSRF),which is supported by the Chinese Academy of Sciences(Grant Nos.KJCX2-SW-N20,and KJCX2-SW-N03)。
文摘The physical properties of most 2D materials are highly dependent on the nature of their interlayer interaction.In-depth studies of the interlayer interaction are beneficial to the understanding of the physical properties of 2D materials and permit the development of related devices.Layered magnetic NiPS_(3)has unique magnetic and electronic properties.The electronic band structure and corresponding magnetic state of NiPS_(3)are expected to be sensitive to the interlayer interaction,which can be tuned by external pressure.Here,we report an insulator-metal transition accompanied by the collapse of magnetic order during the 2D-3D structural crossover induced by hydrostatic pressure.A two-stage phase transition from a monoclinic(C2/m)to a trigonal(P31m)lattice is identified via ab initio simulations and confirmed via high-pressure X-ray diffraction and Raman scattering;this transition corresponds to a layer-by-layer slip mechanism along the a-axis.Temperature-dependent resistance measurements and room temperature infrared spectroscopy under different pressures demonstrate that the insulator-metal transition and the collapse of the magnetic order occur at~20 GPa,which is confirmed by low-temperature Raman scattering measurements and theoretical calculations.These results establish a strong correlation between the structural change,electric transport,and magnetic phase transition and expand our understanding of layered magnetic materials.Moreover,the structural transition caused by the interlayer displacement has significance for designing similar devices at ambient pressure.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant Nos. 2015187, and 2016215)National Natural Science Foundation of China (Grant Nos. 11574338, 11204338, and 11404359)and the ”Strategic Priority Research Program (B)” of the Chinese Academy of Sciences (Grant No. XDB04040300)
文摘The quantum limit, where only the lowest Landau level is occupied by electrons, can be achieved under a high magnetic field when the Landau level splitting is comparable with the Fermi energy. The rather small Fermi pockets and Fermi energy in CaFeAsF reported recently make this compound a good candidate for investigating the electrical transport near the quantum limit.Here, we report high-field experiments up to 65 T on a single-crystalline CaFeAsF, which shows a metal-insulator quantum phase transition tuned by the out-of-plane magnetic field. The obtained critical exponent zν through the finite-size scaling analysis is very close to 4/3. This transition is closely associated with the evolution of electronic states approaching the quantum limit.The resistivity behaviors as a function of field and temperature were evaluated based on Adams-Holstein theory(A-H theory).Moreover, the in-plane component of the field, which does not affect the transport behavior in the classical region, suppressed the magnetoresistance near the quantum limit.
