The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the rever...The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the reversible 2H–1T′phase transition in MoTe_(2)is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles calculations.This phenomenon can be profoundly understood by comparing the Mo–Te bonding strength between the two phases.The 2H-MoTe_(2)has one stronger bonding type,while 1T′-MoTe_(2)has three weaker types of bonds,suggesting bonding inhomogeneity in 1T′-MoTe_(2).Meanwhile,the bonding inhomogeneity can induce more scattering of vibration modes.The weaker bonding indicates a softer structure,resulting in lower phonon group velocity,a shorter phonon relaxation lifetime and larger Gr¨uneisen constants.The impact caused by the 2H to 1T′phase transition in MoTe_(2)hinders the propagation of phonons,thereby reducing thermal conductivity.Our study describes the possibility for the provision of the MoTe_(2)-based controllable and reversible thermal switch device.展开更多
We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junctio...We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.展开更多
Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conduct...Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conductivity of porous metamaterials in the ballistic transport region by using the Lorentz gas model. It is found that the introduction of asymmetry and Gaussian disorder into porous metamaterials can lead to a strong enhancement of thermal conductivity. By dividing the transport process into ballistic transport, non-ballistic transport, and unsuccessful transport processes, we find that the enhancement of thermal conductivity originates from the significant increase ballistic transport ratio. The findings enhance the understanding of ballistic thermal transport in porous materials and may facilitate designs of high-performance porous thermal metamaterials.展开更多
基金the China Scholarship Council(Grant No.202107000030)RIE2020 Advanced Manufacturing and Engineering(AME)Programmatic(Grant No.A1898b0043)A*STAR Aerospace Programme(Grant No.M2115a0092)。
文摘The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the reversible 2H–1T′phase transition in MoTe_(2)is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles calculations.This phenomenon can be profoundly understood by comparing the Mo–Te bonding strength between the two phases.The 2H-MoTe_(2)has one stronger bonding type,while 1T′-MoTe_(2)has three weaker types of bonds,suggesting bonding inhomogeneity in 1T′-MoTe_(2).Meanwhile,the bonding inhomogeneity can induce more scattering of vibration modes.The weaker bonding indicates a softer structure,resulting in lower phonon group velocity,a shorter phonon relaxation lifetime and larger Gr¨uneisen constants.The impact caused by the 2H to 1T′phase transition in MoTe_(2)hinders the propagation of phonons,thereby reducing thermal conductivity.Our study describes the possibility for the provision of the MoTe_(2)-based controllable and reversible thermal switch device.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504084 and 11647164)the Natural Science Foundation for Colleges and Universities in Jiangsu Province,China(Grant Nos.18KJB140005,17KJD170004,and 16KJB140008)
文摘We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11975125 and 11890703)the Department of Science and Technology of Jiangsu Province (Grant No. BK20220032)。
文摘Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conductivity of porous metamaterials in the ballistic transport region by using the Lorentz gas model. It is found that the introduction of asymmetry and Gaussian disorder into porous metamaterials can lead to a strong enhancement of thermal conductivity. By dividing the transport process into ballistic transport, non-ballistic transport, and unsuccessful transport processes, we find that the enhancement of thermal conductivity originates from the significant increase ballistic transport ratio. The findings enhance the understanding of ballistic thermal transport in porous materials and may facilitate designs of high-performance porous thermal metamaterials.
