The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling micro...The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling microscopy measurements and first-principles calculations,we prepare monolayer 1T-TaS2 and TaSe2 and explore their electronic structures at the atomic scale.Both two-dimensional(2D)compounds exhibit commensurate charge density wave phase at low temperature.The conductance mapping identifies the contributions from different Ta atoms to the local density of states with spatial and energy resolution.Both 1T-TaS2 and 1T-TaSe2 monolayer are shown to be insulators,while the former has a Mott gap and the latter is a regular band insulator.展开更多
Charge-density-wave(CDW) materials with strongly correlated electrons have broadband light absorption and ultrafast response to light irradiation, and hence hold great potential in photodetection. 1 T-TaS2 is a typica...Charge-density-wave(CDW) materials with strongly correlated electrons have broadband light absorption and ultrafast response to light irradiation, and hence hold great potential in photodetection. 1 T-TaS2 is a typical CDW material with various thermodynamically CDW ground states at different temperatures and fertile out-of-equilibrium intermediate/hidden states. In particular, the light pulses can trigger melting of CDW ordering and also forms hidden states, which exhibits strikingly different electrical conductivity compared to the ground phase. Here, we review the recent research on phase transitions in 1 T-TaS2 and their potential applications in photodetection. We also discuss the ultrafast melting of CDW ordering by ultrafast laser irradiation and the out-of-equilibrium intermediate/hidden states by optical/electrical pulse. For photodetection, demonstrations of photoconductors and bolometers are introduced. Finally, we discuss some of the challenges that remain.展开更多
We present the magnetoresistance measurements of ultrathin Mn5Ge3 films with different thicknesses at low temperatures. Owing to the lattice mismatch between MnsGe3 and Ge （111）, the thickness of MnsGe3 films has a ...We present the magnetoresistance measurements of ultrathin Mn5Ge3 films with different thicknesses at low temperatures. Owing to the lattice mismatch between MnsGe3 and Ge （111）, the thickness of MnsGe3 films has a significant effect on the magnetoresistance. When the thickness of Mn is more than 72 monolayers （MLs）, the magnetoresistance of the Mn5 Ge3 films appears a peak at about 6 kOe, which shows that the magnetoresistance results from the Anderson weak localization effect and the variable range hopping in the presence of a magnetic field. The magnetic and semiconducting properties indicate that the Mn5 Ge3 film is a potential material for spin injection.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11874233,11622433,and 11574175)the Ministry of Science and Technology of China(Nos.2016YFA0301002 and 2018YFA0305603).
文摘The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling microscopy measurements and first-principles calculations,we prepare monolayer 1T-TaS2 and TaSe2 and explore their electronic structures at the atomic scale.Both two-dimensional(2D)compounds exhibit commensurate charge density wave phase at low temperature.The conductance mapping identifies the contributions from different Ta atoms to the local density of states with spatial and energy resolution.Both 1T-TaS2 and 1T-TaSe2 monolayer are shown to be insulators,while the former has a Mott gap and the latter is a regular band insulator.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673058 and 21822502)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDB-SSW-SYS031)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB30000000)
文摘Charge-density-wave(CDW) materials with strongly correlated electrons have broadband light absorption and ultrafast response to light irradiation, and hence hold great potential in photodetection. 1 T-TaS2 is a typical CDW material with various thermodynamically CDW ground states at different temperatures and fertile out-of-equilibrium intermediate/hidden states. In particular, the light pulses can trigger melting of CDW ordering and also forms hidden states, which exhibits strikingly different electrical conductivity compared to the ground phase. Here, we review the recent research on phase transitions in 1 T-TaS2 and their potential applications in photodetection. We also discuss the ultrafast melting of CDW ordering by ultrafast laser irradiation and the out-of-equilibrium intermediate/hidden states by optical/electrical pulse. For photodetection, demonstrations of photoconductors and bolometers are introduced. Finally, we discuss some of the challenges that remain.
文摘We present the magnetoresistance measurements of ultrathin Mn5Ge3 films with different thicknesses at low temperatures. Owing to the lattice mismatch between MnsGe3 and Ge （111）, the thickness of MnsGe3 films has a significant effect on the magnetoresistance. When the thickness of Mn is more than 72 monolayers （MLs）, the magnetoresistance of the Mn5 Ge3 films appears a peak at about 6 kOe, which shows that the magnetoresistance results from the Anderson weak localization effect and the variable range hopping in the presence of a magnetic field. The magnetic and semiconducting properties indicate that the Mn5 Ge3 film is a potential material for spin injection.
