Detection of local strain at the nanometer scale with high sensitivity remains challenging.Here we report near-field infrared nano-imaging of local strains in bilayer graphene by probing strain-induced shifts of phono...Detection of local strain at the nanometer scale with high sensitivity remains challenging.Here we report near-field infrared nano-imaging of local strains in bilayer graphene by probing strain-induced shifts of phonon frequency.As a non-polar crystal,intrinsic bilayer graphene possesses little infrared response at its transverse optical phonon frequency.The reported optical detection of local strain is enabled by applying a vertical electrical field that breaks the symmetry of the two graphene layers and introduces finite electrical dipole moment to graphene phonon.The activated phonon further interacts with continuum electronic transitions,and generates a strong Fano resonance.The resulted Fano resonance features a very sharp near-field infrared scattering peak,which leads to an extraordinary sensitivity of-0.002%for the strain detection.Our results demonstrate the first nano-scale near-field Fano resonance,provide a new way to probe local strains with high sensitivity in non-polar crystals,and open exciting possibilities for studying strain-induced rich phenomena.展开更多
Lattice superlattices constructed with different materials such as ferromagnets and insulators at atomic scale provide an ideal platform for exploring many emergent physical phenomena.In the present work,a new type of...Lattice superlattices constructed with different materials such as ferromagnets and insulators at atomic scale provide an ideal platform for exploring many emergent physical phenomena.In the present work,a new type of superlattices composed of ferromagnetic half-metal CrO_(2),with a thickness of two atomic layers,together with insulating MgH_(2) are constructed.Systematic theoretical studies on the(CrO_(2))_(2)/(MgH_(2))_(n) (n=2,3,4,5,6)superlattices are carried out based on first-principles density-functional theory calculations.These superlattices are ferromagnetic semiconductors with similar intra-layer magnetic exchange couplings between Cr ions.As the thickness of the MgH_(2) layer increases,the magnetic exchange interaction between inter-layer Cr ions shows oscillating decaying behavior,while the energy band gaps show a small increase.The understanding of magnetic couplings in these superlattices provides a pathway for constructing new ferromagnetic semiconductors.展开更多
基金Supported by the National Key Research and Development Program of China (Grant No.2016YFA0302001)the National Natural Science Foundation of China (Grant Nos.11774224,12074244,11521404,and 61701394)+1 种基金support from the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learningadditional support from a Shanghai talent program。
文摘Detection of local strain at the nanometer scale with high sensitivity remains challenging.Here we report near-field infrared nano-imaging of local strains in bilayer graphene by probing strain-induced shifts of phonon frequency.As a non-polar crystal,intrinsic bilayer graphene possesses little infrared response at its transverse optical phonon frequency.The reported optical detection of local strain is enabled by applying a vertical electrical field that breaks the symmetry of the two graphene layers and introduces finite electrical dipole moment to graphene phonon.The activated phonon further interacts with continuum electronic transitions,and generates a strong Fano resonance.The resulted Fano resonance features a very sharp near-field infrared scattering peak,which leads to an extraordinary sensitivity of-0.002%for the strain detection.Our results demonstrate the first nano-scale near-field Fano resonance,provide a new way to probe local strains with high sensitivity in non-polar crystals,and open exciting possibilities for studying strain-induced rich phenomena.
基金supported by the National Natural Science Foundation of China (Grant No. 11521404)the Materials Genome Initiative Center of Shanghai Jiao Tong University (SJTU)。
文摘Lattice superlattices constructed with different materials such as ferromagnets and insulators at atomic scale provide an ideal platform for exploring many emergent physical phenomena.In the present work,a new type of superlattices composed of ferromagnetic half-metal CrO_(2),with a thickness of two atomic layers,together with insulating MgH_(2) are constructed.Systematic theoretical studies on the(CrO_(2))_(2)/(MgH_(2))_(n) (n=2,3,4,5,6)superlattices are carried out based on first-principles density-functional theory calculations.These superlattices are ferromagnetic semiconductors with similar intra-layer magnetic exchange couplings between Cr ions.As the thickness of the MgH_(2) layer increases,the magnetic exchange interaction between inter-layer Cr ions shows oscillating decaying behavior,while the energy band gaps show a small increase.The understanding of magnetic couplings in these superlattices provides a pathway for constructing new ferromagnetic semiconductors.
