We report transport measurements on Josephson junctions consisting of Bi_(2)Te_(3) topological insulator(TI)thin films contacted by superconducting Nb electrodes.For a device with junction length L=134 nm,the critical...We report transport measurements on Josephson junctions consisting of Bi_(2)Te_(3) topological insulator(TI)thin films contacted by superconducting Nb electrodes.For a device with junction length L=134 nm,the critical supercurrent Ic can be modulated by an electrical gate which tunes the carrier type and density of the TI film.Ic can reach a minimum when the TI is near the charge neutrality regime with the Fermi energy lying close to the Dirac point of the surface state.In the p-type regime the Josephson current can be well described by a short ballistic junction model.In the n-type regime the junction is ballistic at 0.7 K<T<3.8 K while for T<0.7 K the diffusive bulk modes emerge and contribute a larger Ic than the ballistic model.We attribute the lack of diffusive bulk modes in the p-type regime to the formation of p-n junctions.Our work provides new clues for search of Majorana zero mode in TI-based superconducting devices.展开更多
Two-dimensional(2D)magnets provide an ideal platform to explore new physical phenomena in fundamental magnetism and to realize the miniaturization of magnetic devices.The study on its domain structure evolution with t...Two-dimensional(2D)magnets provide an ideal platform to explore new physical phenomena in fundamental magnetism and to realize the miniaturization of magnetic devices.The study on its domain structure evolution with thickness is of great significance for better understanding the 2D magnetism.Here,we investigate the magnetization reversal and domain structure evolution in 2D ferromagnet Fe_(3)GeTe_(2)(FGT)with a thickness range of 11.2-112 nm.Three types of domain structures and their corresponding hysteresis loops can be obtained.The magnetic domain varies from a circular domain via a dendritic domain to a labyrinthian domain with increasing FGT thickness,which is accompanied by a transition from squared to slanted hysteresis loops with reduced coercive fields.These features can be ascribed to the total energy changes from exchange interaction-dominated to dipolar interaction-dominated with increasing FGT thickness.Our finding not only enriches the fundamental magnetism,but also paves a way towards spintronics based on 2D magnet.展开更多
The big data explosion demands novel data storage technology. Among many different approaches, solitonic racetrack memory devices hold great promise for accommodating nonvolatile and low-power functionalities. As repr...The big data explosion demands novel data storage technology. Among many different approaches, solitonic racetrack memory devices hold great promise for accommodating nonvolatile and low-power functionalities. As representative topological solitons, magnetic skyrmions are envisioned as potential information carriers for efficient information processing. While their advantages as memory and logic elements have been vastly exploited from theoretical perspectives, the corresponding experimental efforts are rather limited. These challenges, which are key to versatile skyrmionic devices, will be studied in this work. Through patterning concaved surface topography with designed arrays of indentations on standard Si/SiO_(2) substrates, we demonstrate that the resultant non-flat energy landscape could lead to the formation of hexagonal and square skyrmion lattices in Ta/CoFeB/MgO multilayers. Based on these films, one-dimensional racetrack devices are subsequently fabricated, in which a long-distance deterministic shifting of skyrmions between neighboring indentations is achieved at room temperature. Through separating the word line and the bit line, a prototype shift register device, which can sequentially generate and precisely shift complex skyrmionic data strings, is presented. The deterministic writing and longdistance shifting of skyrmionic bits can find potential applications in transformative skyrmionic memory,logic as well as the in-memory computing devices.展开更多
基金Supported by the Basic Science Center Project of the National Natural Science Foundation of China(Grant No.51788104)the National Key R&D Program of China(Grant No.2017YFA0302900)。
文摘We report transport measurements on Josephson junctions consisting of Bi_(2)Te_(3) topological insulator(TI)thin films contacted by superconducting Nb electrodes.For a device with junction length L=134 nm,the critical supercurrent Ic can be modulated by an electrical gate which tunes the carrier type and density of the TI film.Ic can reach a minimum when the TI is near the charge neutrality regime with the Fermi energy lying close to the Dirac point of the surface state.In the p-type regime the Josephson current can be well described by a short ballistic junction model.In the n-type regime the junction is ballistic at 0.7 K<T<3.8 K while for T<0.7 K the diffusive bulk modes emerge and contribute a larger Ic than the ballistic model.We attribute the lack of diffusive bulk modes in the p-type regime to the formation of p-n junctions.Our work provides new clues for search of Majorana zero mode in TI-based superconducting devices.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFA0206202 and 2019YFA0308000)the National Natural Science Foundation of China(Grant Nos.51871130,62022089,and 11874405)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2019007)。
文摘Two-dimensional(2D)magnets provide an ideal platform to explore new physical phenomena in fundamental magnetism and to realize the miniaturization of magnetic devices.The study on its domain structure evolution with thickness is of great significance for better understanding the 2D magnetism.Here,we investigate the magnetization reversal and domain structure evolution in 2D ferromagnet Fe_(3)GeTe_(2)(FGT)with a thickness range of 11.2-112 nm.Three types of domain structures and their corresponding hysteresis loops can be obtained.The magnetic domain varies from a circular domain via a dendritic domain to a labyrinthian domain with increasing FGT thickness,which is accompanied by a transition from squared to slanted hysteresis loops with reduced coercive fields.These features can be ascribed to the total energy changes from exchange interaction-dominated to dipolar interaction-dominated with increasing FGT thickness.Our finding not only enriches the fundamental magnetism,but also paves a way towards spintronics based on 2D magnet.
基金supported by the National Natural Science Foundation of China under the distinguished Young Scholar program(12225409)the Basic Science Center Project (51788104)+6 种基金the National Key R&D Program of China (2022YFA1405100)the National Key R&D Program of China (2022YFA1403300)the National Natural Science Foundation of China (52271181, 51831005, and 11861131008)supported by the National Natural Science Foundation of China (12204107)the Innovation Program for Quantum Science and Technology (2023ZD0300500)Shanghai Pujiang Program (21PJ1401500)Shanghai Science and Technology Committee (21JC1406200)。
文摘The big data explosion demands novel data storage technology. Among many different approaches, solitonic racetrack memory devices hold great promise for accommodating nonvolatile and low-power functionalities. As representative topological solitons, magnetic skyrmions are envisioned as potential information carriers for efficient information processing. While their advantages as memory and logic elements have been vastly exploited from theoretical perspectives, the corresponding experimental efforts are rather limited. These challenges, which are key to versatile skyrmionic devices, will be studied in this work. Through patterning concaved surface topography with designed arrays of indentations on standard Si/SiO_(2) substrates, we demonstrate that the resultant non-flat energy landscape could lead to the formation of hexagonal and square skyrmion lattices in Ta/CoFeB/MgO multilayers. Based on these films, one-dimensional racetrack devices are subsequently fabricated, in which a long-distance deterministic shifting of skyrmions between neighboring indentations is achieved at room temperature. Through separating the word line and the bit line, a prototype shift register device, which can sequentially generate and precisely shift complex skyrmionic data strings, is presented. The deterministic writing and longdistance shifting of skyrmionic bits can find potential applications in transformative skyrmionic memory,logic as well as the in-memory computing devices.
