The reversal of perpendicular magnetization(PM)by electric control is crucial for high-density integration of low-power magnetic random-access memory.Although the spin-transfer torque and spin-orbit torque technologie...The reversal of perpendicular magnetization(PM)by electric control is crucial for high-density integration of low-power magnetic random-access memory.Although the spin-transfer torque and spin-orbit torque technologies have been used to switch the magnetization of a free layer with perpendicular magnetic anisotropy,the former has limited endurance because of the high current density directly through the junction,while the latter requires an external magnetic field or unconventional configuration to break the symmetry.Here we propose and realize the orbit-transfer torque(OTT),that is,exerting torque on the magnetization using the orbital magnetic moments,and thus demonstrate a new strategy for current-driven PM reversal without external magnetic field.The perpendicular polarization of orbital magnetic moments is generated by a direct current in a few-layer WTe_(2)due to the existence of nonzero Berry curvature dipole,and the polarization direction can be switched by changing the current polarity.Guided by this principle,we construct the WTe_(2)/Fe_(3)GeTe_(2)heterostructures to achieve the OTT driven field-free deterministic switching of PM.展开更多
We report an efficient and economical way for mass production of large-scale graphene films with high quality and uniformity.By using the designed scrolled copper-graphite structure,a continuous graphene film with typ...We report an efficient and economical way for mass production of large-scale graphene films with high quality and uniformity.By using the designed scrolled copper-graphite structure,a continuous graphene film with typical area of 200×39 cm^2 could be obtained in 15 min,and the production rate of the graphene film and space utilization rate of the CVD reactor can reach 520 cm 2⋅min−1 and 0.38 cm−1⋅min−1,respectively.Our method provides a guidance for the industrial production of graphene films,and may also accelerate its large-scale applications.展开更多
Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterizatio...Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterization,and optical imaging.Investigating and manipulating the nonlinear optical response of target materials lead us to reveal hidden physics and develop applications in optical devices.Here,we report the realization of facile manipulation of nonlinear optical responses in the example system of MoS_(2) monolayer by van der Waals interfacial engineering.We found that,the interfacing of monolayer graphene will weaken the exciton oscillator strength in MoS_(2) monolayer and correspondingly suppress the second harmonic generation(SHG)intensity to 30%under band-gap resonance excitation.While with off-resonance excitation,the SHG intensity would enhance up to 130%,which is conjectured to be induced by the interlayer excitation between MoS_(2) and graphene.Our investigation provides an effective method for controlling nonlinear optical properties of two-dimensional materials and therefore facilitates their future applications in optoelectronic and photonic devices.展开更多
Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been...Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been vastly and clearly studied,the dynamic process of its photoexcited carrier states mainly remains elusive.Here,we unveil the photoexcited hot carrier dynamics in TBG by time-resolved ultrafast photoluminescence(PL)autocorrelation spectroscopy.We demonstrate the unconventional ultrafast PL emission between the van Hove singularities(VHSs)with a~4 times prolonged relaxation lifetime.This intriguing photoexcited carrier behavior is ascribed to the abnormal hot carrier thermalization brought by bottleneck effects at VHSs and interlayer charge distribution process.Our study on hot carrier dynamics in TBG offers new insights into the excited states and correlated physics of graphene twistronics systems.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.91964201 and 61825401)。
文摘The reversal of perpendicular magnetization(PM)by electric control is crucial for high-density integration of low-power magnetic random-access memory.Although the spin-transfer torque and spin-orbit torque technologies have been used to switch the magnetization of a free layer with perpendicular magnetic anisotropy,the former has limited endurance because of the high current density directly through the junction,while the latter requires an external magnetic field or unconventional configuration to break the symmetry.Here we propose and realize the orbit-transfer torque(OTT),that is,exerting torque on the magnetization using the orbital magnetic moments,and thus demonstrate a new strategy for current-driven PM reversal without external magnetic field.The perpendicular polarization of orbital magnetic moments is generated by a direct current in a few-layer WTe_(2)due to the existence of nonzero Berry curvature dipole,and the polarization direction can be switched by changing the current polarity.Guided by this principle,we construct the WTe_(2)/Fe_(3)GeTe_(2)heterostructures to achieve the OTT driven field-free deterministic switching of PM.
基金Supported by the Beijing Natural Science Foundation(Grant No.JQ19004)the Key R&D Program of Guangdong Province(Grant Nos.2019B010931001,2020B010189001,2018B010109009 and 2018B030327001)+9 种基金Bureau of Industry and Information Technology of Shenzhen(Graphene platform 201901161512)the National Natural Science Foundation of China(Grant Nos.51991340,51991342 and 51522201)the National Key R&D Program of China(Grant Nos.2016YFA0300903 and 2016YFA0300804)the Beijing Excellent Talents Training Support(Grant No.2017000026833ZK11)the Beijing Municipal Science&Technology Commission(Grant No.Z191100007219005)the Beijing Graphene Innovation Program(Z181100004818003)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06D348)the Science,Technology and Innovation Commission of Shenzhen Municipality(Grant No.KYTDPT20181011104202253)the National Postdoctoral Program for Innovative Talents(Grant No.BX20190016)China Postdoctoral Science Foundation(Grant Nos.2019M660280 and 2019M660281).
文摘We report an efficient and economical way for mass production of large-scale graphene films with high quality and uniformity.By using the designed scrolled copper-graphite structure,a continuous graphene film with typical area of 200×39 cm^2 could be obtained in 15 min,and the production rate of the graphene film and space utilization rate of the CVD reactor can reach 520 cm 2⋅min−1 and 0.38 cm−1⋅min−1,respectively.Our method provides a guidance for the industrial production of graphene films,and may also accelerate its large-scale applications.
基金Project supported by Beijing Natural Science Foundation,China(Grant No.JQ19004)Beijing Excellent Talents Training Support,China(Grant No.2017000026833ZK11)+8 种基金the National Natural Science Foundation of China(Grant Nos.52025023,51991340,and 51991342)the National Key Research and Development Program of China(Grant Nos.2016YFA0300903 and 2016YFA0300804)the Key R&D Program of Guangdong Province,China(Grant Nos.2019B010931001,2020B010189001,2018B010109009,and 2018B030327001)the Beijing Municipal Science&Technology Commission,China(Grant No.Z191100007219005)the Beijing Graphene Innovation Program(Grant No.Z181100004818003)Bureau of Industry and Information Technology of Shenzhen(Graphene platform 201901161512)Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06D348)the Science,Technology and Innovation Commission of Shenzhen Municipality(Grant No.KYTDPT20181011104202253)the China Postdoctoral Science Foundation(Grant No.2020M680177)。
文摘Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterization,and optical imaging.Investigating and manipulating the nonlinear optical response of target materials lead us to reveal hidden physics and develop applications in optical devices.Here,we report the realization of facile manipulation of nonlinear optical responses in the example system of MoS_(2) monolayer by van der Waals interfacial engineering.We found that,the interfacing of monolayer graphene will weaken the exciton oscillator strength in MoS_(2) monolayer and correspondingly suppress the second harmonic generation(SHG)intensity to 30%under band-gap resonance excitation.While with off-resonance excitation,the SHG intensity would enhance up to 130%,which is conjectured to be induced by the interlayer excitation between MoS_(2) and graphene.Our investigation provides an effective method for controlling nonlinear optical properties of two-dimensional materials and therefore facilitates their future applications in optoelectronic and photonic devices.
基金supported by the National Key R&D Program of China(2021YFA1400201,2022YFA1403504,2021YFB32003032021YFA1400502)+4 种基金the National Natural Science Foundation of China(T2188101,52025023,51991342,52021006,92163206,11888101,and 12374167)Guangdong Major Project of Basic and Applied Basic Research(2021B0301030002)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB33000000)the Pearl River Talent Recruitment Program of Guangdong Province(2019ZT08C321)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Interlayer twist evokes revolutionary changes to the optical and electronic properties of twisted bilayer graphene(TBG)for electronics,photonics and optoelectronics.Although the ground state responses in TBG have been vastly and clearly studied,the dynamic process of its photoexcited carrier states mainly remains elusive.Here,we unveil the photoexcited hot carrier dynamics in TBG by time-resolved ultrafast photoluminescence(PL)autocorrelation spectroscopy.We demonstrate the unconventional ultrafast PL emission between the van Hove singularities(VHSs)with a~4 times prolonged relaxation lifetime.This intriguing photoexcited carrier behavior is ascribed to the abnormal hot carrier thermalization brought by bottleneck effects at VHSs and interlayer charge distribution process.Our study on hot carrier dynamics in TBG offers new insights into the excited states and correlated physics of graphene twistronics systems.
