Semiconductor moirésuperlattices provide great platforms for exploring exotic collective excitations.Optical Stark effect,a shift of the electronic transition in the presence of a light field,provides an ultrafas...Semiconductor moirésuperlattices provide great platforms for exploring exotic collective excitations.Optical Stark effect,a shift of the electronic transition in the presence of a light field,provides an ultrafast and coherent method of manipulating matter states,which,however,has not been demonstrated in moirématerials.Here,we report the valleyselective optical Stark effect of moiréexcitons in the WSe_(2)/WS_(2)superlattice by using transient reflection spectroscopy.Prominent valley-selective energy shifts up to 7.8 meV have been observed for moiréexcitons,corresponding to pseudomagnetic fields as large as 34 T.Our results provide a route to coherently manipulate exotic states in moirésuperlattices.展开更多
Interfacial ferroelectricity is a recently established mechanism for generating spontaneous reversible electric polarization,arising from the charge transfer between stacked van der Waals layered atomic crystals.It ha...Interfacial ferroelectricity is a recently established mechanism for generating spontaneous reversible electric polarization,arising from the charge transfer between stacked van der Waals layered atomic crystals.It has been realized in both naturally formed multilayer crystals and moirésuperlattices.Owing to the large number of material choices and combinations,this approach is highly versatile,greatly expanding the scope of ultrathin ferroelectrics.A key advantage of interfacial ferroelectricity is its potential to couple with preexisting properties of the constituent layers,enabling their electrical manipulation through ferroelectric switching and paving the way for advanced device functionalities.This review article summarizes recent experimental progress in interfacial ferroelectricity,with an emphasis on its coupling with a variety of electronic properties.After introducing the underlying mechanism of interfacial ferroelectricity and the range of material systems discovered to date,we highlight selected examples showcasing ferroelectric control of excitonic optical properties,Berry curvature effects,and superconductivity.We also discuss the challenges and opportunities that await further studies in this field.展开更多
We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge u...We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge under the inversion symmetry breaking introduced by an effective mass imbalance between the two layers or a moiré potential in one layer, as well as under the time-reversal symmetry breaking realized by applying a magnetic field. Considering the wide tunability of layered materials, the frequencies and chirality of phonons can both be tuned by varying the system parameters. These findings suggest that bilayer honeycomb-type Wigner crystals can serve as an exciting new platform for studying chiral phonons.展开更多
In this study, the residual strain of a thin conductive metal wire on a polymer substrate after electrical failure is measured with SEM moir′e. Focused ion beam(FIB) milling is applied to fabricate micron moir′e gra...In this study, the residual strain of a thin conductive metal wire on a polymer substrate after electrical failure is measured with SEM moir′e. Focused ion beam(FIB) milling is applied to fabricate micron moir′e gratings on the surfaces of constantan wires and the random phase shifting technique is used to process moir′e fringes. The virtual strain method is briefly introduced and used to calculate the real strain of specimens. In order to study the influence of a defect on the electrical failure of the constantan wire, experiments were conducted on two specimens, one with a crack, while the other one without any crack. By comparing the results, we found that the defect makes the critical beam current of electrical failure decrease. In addition, the specimens were subjected to compression after electrical failure, in agreement with the observed crack closure of the specimen. The successful results demonstrate that the moir′e method is effective to characterize the full-field deformation of constantan wires on the polymer membrane, and has a good potential for further application to the deformation measurement of thin films.展开更多
基金Project supported by the National Key R&D Program of China(Grant Nos.2022YFA1402400 and 2022YFA1405400)the National Natural Science Foundation of China(Grant Nos.11934011 and 12274365)+3 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LR24A040001)Open project of Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education)of Shanghai Jiao Tong Universitysupport from the JSPS KAKENHI(Grant Nos.20H00354 and 23H02052)World Premier International Research Center Initiative(WPI),MEXT,Japan。
文摘Semiconductor moirésuperlattices provide great platforms for exploring exotic collective excitations.Optical Stark effect,a shift of the electronic transition in the presence of a light field,provides an ultrafast and coherent method of manipulating matter states,which,however,has not been demonstrated in moirématerials.Here,we report the valleyselective optical Stark effect of moiréexcitons in the WSe_(2)/WS_(2)superlattice by using transient reflection spectroscopy.Prominent valley-selective energy shifts up to 7.8 meV have been observed for moiréexcitons,corresponding to pseudomagnetic fields as large as 34 T.Our results provide a route to coherently manipulate exotic states in moirésuperlattices.
基金Project supported by the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20231529 and BK20233001)the National Key Research and Development Program of China(Grant No.2024YFA1409100)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.0204-14380233)the National Natural Science Foundation of China(Grant Nos.12474170 and 123B2059)the National Postdoctoral Program for Innovative Talents(Grant No.BX20240160)。
文摘Interfacial ferroelectricity is a recently established mechanism for generating spontaneous reversible electric polarization,arising from the charge transfer between stacked van der Waals layered atomic crystals.It has been realized in both naturally formed multilayer crystals and moirésuperlattices.Owing to the large number of material choices and combinations,this approach is highly versatile,greatly expanding the scope of ultrathin ferroelectrics.A key advantage of interfacial ferroelectricity is its potential to couple with preexisting properties of the constituent layers,enabling their electrical manipulation through ferroelectric switching and paving the way for advanced device functionalities.This review article summarizes recent experimental progress in interfacial ferroelectricity,with an emphasis on its coupling with a variety of electronic properties.After introducing the underlying mechanism of interfacial ferroelectricity and the range of material systems discovered to date,we highlight selected examples showcasing ferroelectric control of excitonic optical properties,Berry curvature effects,and superconductivity.We also discuss the challenges and opportunities that await further studies in this field.
基金supported by Tencent’s Program of Aspiring Explorers in Sciencesupport by the National Natural Science Foundation of China (Grant No. 12274477)the Department of Science and Technology of Guangdong Province in China (Grant No. 2019QN01X061)。
文摘We theoretically investigated the chiral phonons of honeycomb-type bilayer Wigner crystals recently discovered in van der Waals structures of layered transition metal dichalcogenides. These chiral phonons can emerge under the inversion symmetry breaking introduced by an effective mass imbalance between the two layers or a moiré potential in one layer, as well as under the time-reversal symmetry breaking realized by applying a magnetic field. Considering the wide tunability of layered materials, the frequencies and chirality of phonons can both be tuned by varying the system parameters. These findings suggest that bilayer honeycomb-type Wigner crystals can serve as an exciting new platform for studying chiral phonons.
基金Project supported by the National Natural Science Foundation of China(Nos.11232008,11227801 and 11302082)the Doctoral Program of University of Jinan(No.XBS1307)
文摘In this study, the residual strain of a thin conductive metal wire on a polymer substrate after electrical failure is measured with SEM moir′e. Focused ion beam(FIB) milling is applied to fabricate micron moir′e gratings on the surfaces of constantan wires and the random phase shifting technique is used to process moir′e fringes. The virtual strain method is briefly introduced and used to calculate the real strain of specimens. In order to study the influence of a defect on the electrical failure of the constantan wire, experiments were conducted on two specimens, one with a crack, while the other one without any crack. By comparing the results, we found that the defect makes the critical beam current of electrical failure decrease. In addition, the specimens were subjected to compression after electrical failure, in agreement with the observed crack closure of the specimen. The successful results demonstrate that the moir′e method is effective to characterize the full-field deformation of constantan wires on the polymer membrane, and has a good potential for further application to the deformation measurement of thin films.
