Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging ...Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging of materials.Scanning SQUID microscopy(SSM)combines both high spatial resolution and high magnetic field sensitivity and is especially suitable for studying low dimensional materials with small sensing volumes.Here,we briefly review the fabrication of different types of nano-SQUIDs and the recent progress of utilizing them for scanning microscopy of quantum materials.We focus on but are not limited to topological states,unconventional superconductivity and exotic magnetism with a particular interest in two-dimensional materials.The magnet-ometry,susceptometry and current imaging modes of the SSM coupled with the external tuning of the material by magnetic field,electrical field gating and strain reveals a multitude of information beyond the scopes of charge-sensing probes.展开更多
In two-dimensional(2D) ferromagnets, anisotropy is essential for the magnetic ordering as dictated by the Mermin-Wagner theorem. But when competing anisotropies are present, the phase transition becomes nontrivial. He...In two-dimensional(2D) ferromagnets, anisotropy is essential for the magnetic ordering as dictated by the Mermin-Wagner theorem. But when competing anisotropies are present, the phase transition becomes nontrivial. Here, utilizing highly sensitive susceptometry of scanning superconducting quantum interference device microscopy, we probe the spin correlations of ABC-stacked Cr Br3under zero magnetic field. We identify a plateau feature in susceptibility above the critical temperature(TC) in thick samples.It signifies a crossover regime induced by the competition between easy-plane intralayer exchange anisotropy versus uniaxial interlayer anisotropy. The evolution of the critical behavior from the bulk to 2D shows that the competition between the anisotropies is magnified in the reduced dimension. It leads to a strongly frustrated ferromagnetic transition in the bilayer with fluctuation on the order of TC, which is distinct from both the monolayer and the bulk. Our observation demonstrates unconventional 2D critical behavior on a honeycomb lattice.展开更多
基金Yihua Wang would like to acknowledge support by Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the National Key R&D Program of China(Grant No.2021YFA1400100)+2 种基金the National Natural Science Foundation of China(Grant No.12150003)Hao Li thanks the National Natural Science Foundation of China(Grant No.62201556)the Shanghai Pujiang Program(Grant No.22PJ1415200)for financial support.
文摘Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging of materials.Scanning SQUID microscopy(SSM)combines both high spatial resolution and high magnetic field sensitivity and is especially suitable for studying low dimensional materials with small sensing volumes.Here,we briefly review the fabrication of different types of nano-SQUIDs and the recent progress of utilizing them for scanning microscopy of quantum materials.We focus on but are not limited to topological states,unconventional superconductivity and exotic magnetism with a particular interest in two-dimensional materials.The magnet-ometry,susceptometry and current imaging modes of the SSM coupled with the external tuning of the material by magnetic field,electrical field gating and strain reveals a multitude of information beyond the scopes of charge-sensing probes.
基金support by the National Key R&D Program of China (2021YFA1400100)the National Natural Science Foundation of China (11827805 and 12150003)+12 种基金Shanghai Municipal Science and Technology Major Project (2019SHZDZX01)support by the National Key R&D Program of China (2018YFE0202600)Beijing Natural Science Foundation (Z200005)support from JSPS KAKENHI (19H05790, 20H00354, and 21H05233)A3 Foresight by JSPSfinancial support from the National Natural Science Foundation of China (11874115)financial support from the Ministry of Science and Technology (MOST) of China (2018YFE0202700)the National Natural Science Foundation of China (11974422)the Strategic Priority Research Program of Chinese Academy of Sciences (XDB30000000)the Fundamental Research Funds for the Central Universities, Chinathe Research Funds of Renmin University of China (22XNKJ30)supported by the National Natural Science Foundation of China (12104504)the China Postdoctoral Science Foundation (2021 M693479)。
文摘In two-dimensional(2D) ferromagnets, anisotropy is essential for the magnetic ordering as dictated by the Mermin-Wagner theorem. But when competing anisotropies are present, the phase transition becomes nontrivial. Here, utilizing highly sensitive susceptometry of scanning superconducting quantum interference device microscopy, we probe the spin correlations of ABC-stacked Cr Br3under zero magnetic field. We identify a plateau feature in susceptibility above the critical temperature(TC) in thick samples.It signifies a crossover regime induced by the competition between easy-plane intralayer exchange anisotropy versus uniaxial interlayer anisotropy. The evolution of the critical behavior from the bulk to 2D shows that the competition between the anisotropies is magnified in the reduced dimension. It leads to a strongly frustrated ferromagnetic transition in the bilayer with fluctuation on the order of TC, which is distinct from both the monolayer and the bulk. Our observation demonstrates unconventional 2D critical behavior on a honeycomb lattice.
