ABC-stacked trilayer graphene has exhibited a variety of correlated phenomena owing to its relatively flat bands and gate-tunable bandgap.However,convenient methods are still lacking for identifying ABC graphene with ...ABC-stacked trilayer graphene has exhibited a variety of correlated phenomena owing to its relatively flat bands and gate-tunable bandgap.However,convenient methods are still lacking for identifying ABC graphene with nanometer-scale resolution.Here we demonstrate that the scanning near-field optical microscope working in ambient conditions can provide quick recognition of ABC trilayer graphene with no ambiguity and excellent resolution(∼20 nm).The recognition is based on the difference in their near-field infrared(IR)responses between the ABA and ABC trilayers.We show that in most frequencies,the response of the ABC trilayer is weaker than the ABA trilayer.However,near the graphene phonon frequency(∼1585 cm−1),ABC’s response increases dramatically when gated and exhibits a narrow and sharp Fano-shape resonant line,whereas the ABA trilayer is largely featherless.Consequently,the IR contrast between ABC and ABA becomes reversed and can even be striking(ABC/ABA∼3)near the graphene phonon frequency.The observed near-field IR features can serve as a golden rule to quickly distinguish ABA and ABC trilayers with no ambiguity,which could largely advance the exploration of correlation physics in ABC-stacked trilayer graphene.展开更多
Herein,we report on the guest-responsive hierarchical self-assembly of dissymmetric cage DC-1 with an intrinsic dipole along its C_(3)-symmetric axis.DC-1 molecules self-assemble into supramolecular columns with themo...Herein,we report on the guest-responsive hierarchical self-assembly of dissymmetric cage DC-1 with an intrinsic dipole along its C_(3)-symmetric axis.DC-1 molecules self-assemble into supramolecular columns with themolecular dipoles aligned along the columnar axis.Mediated by different host-guest interactions of ethyl acetate(EtOAc)and chloroform(CHCl_(3)),the columns are arranged in an antiparallel and parallel fashion,respectively,leading to a switch of the centrosym metric and noncentrosymmetric superstructures.The symmetry of themolecular packing of DC-1 molecules of the noncentrosymmetric crystalline phase is therefore broken,producing a supramolecular ferroelectric with second-harmonic generation and piezoelectric responses.We demonstrate that cages can serve as promising building blocks for the discovery of supramolecular materials with emergent functions and properties,including but not limited to,organic ferroelectrics and nonlinear optics.展开更多
基金supported by the Open Research Fund of Songshan Lake Materials Laboratory(No.2021SLABFK07)the National Key R&D Program of China(No.2021YFA1202902)+2 种基金the National Natural Science Foundation of China(No.12074244)Z S acknowledges support from SJTU(21X010200846)additional support from a Shanghai talent program.
文摘ABC-stacked trilayer graphene has exhibited a variety of correlated phenomena owing to its relatively flat bands and gate-tunable bandgap.However,convenient methods are still lacking for identifying ABC graphene with nanometer-scale resolution.Here we demonstrate that the scanning near-field optical microscope working in ambient conditions can provide quick recognition of ABC trilayer graphene with no ambiguity and excellent resolution(∼20 nm).The recognition is based on the difference in their near-field infrared(IR)responses between the ABA and ABC trilayers.We show that in most frequencies,the response of the ABC trilayer is weaker than the ABA trilayer.However,near the graphene phonon frequency(∼1585 cm−1),ABC’s response increases dramatically when gated and exhibits a narrow and sharp Fano-shape resonant line,whereas the ABA trilayer is largely featherless.Consequently,the IR contrast between ABC and ABA becomes reversed and can even be striking(ABC/ABA∼3)near the graphene phonon frequency.The observed near-field IR features can serve as a golden rule to quickly distinguish ABA and ABC trilayers with no ambiguity,which could largely advance the exploration of correlation physics in ABC-stacked trilayer graphene.
基金supported by the Shanghai Natural Science Foundation(no.18ZR1420800)National Natural Science Foundation of China(no.21890733,22071153).
文摘Herein,we report on the guest-responsive hierarchical self-assembly of dissymmetric cage DC-1 with an intrinsic dipole along its C_(3)-symmetric axis.DC-1 molecules self-assemble into supramolecular columns with themolecular dipoles aligned along the columnar axis.Mediated by different host-guest interactions of ethyl acetate(EtOAc)and chloroform(CHCl_(3)),the columns are arranged in an antiparallel and parallel fashion,respectively,leading to a switch of the centrosym metric and noncentrosymmetric superstructures.The symmetry of themolecular packing of DC-1 molecules of the noncentrosymmetric crystalline phase is therefore broken,producing a supramolecular ferroelectric with second-harmonic generation and piezoelectric responses.We demonstrate that cages can serve as promising building blocks for the discovery of supramolecular materials with emergent functions and properties,including but not limited to,organic ferroelectrics and nonlinear optics.
