Up-conversion photoluminescence(UCPL)refers to the elementary process where low-energy photons are converted into high-energy ones via consecutive interactions inside a medium.When additional energy is provided by int...Up-conversion photoluminescence(UCPL)refers to the elementary process where low-energy photons are converted into high-energy ones via consecutive interactions inside a medium.When additional energy is provided by intermnal thermal energy in the form of lttice vibrations(phonons),the process is called phonon-assisted UCPL.Here,we report the exceptionally large phonon-assisted energy gain of up to^8kgT(kg is Boltzmann constant,T is temperature)on all-inorganic lead halide perovskite semiconductor colloidal nanocrystals that goes beyond the maximum capabilty of only harvesting optical phonon modes.By systematic optical study in combination with a statistical probability model,we explained the nontrivial phonon-assisted UCPL process in perovskites nanocrystals,where in addition to the strong electron-phonon(light-matter)coupling,other nonlinear processes such as phonon-phonon(matter-matter)interaction also effectively boost the up-conversion efficiency.展开更多
Introducing magnetic dopants into twodimensional transition metal dichalcogenides has recently attracted considerable attention due to its promising applications in spintronics and valleytronics.Herein we realized man...Introducing magnetic dopants into twodimensional transition metal dichalcogenides has recently attracted considerable attention due to its promising applications in spintronics and valleytronics.Herein we realized manganese-doped molybdenum diselenide(MoSe_(2))single crystal via chemical vapor transport(CVT)reaction,containing up to 2.9%(atomic concentration)Mn dopants,and investigated the light-matter interaction in these samples.We observed a suppressed trion intensity,a longer photoluminescence lifetime,and prominent blue-and red-shift of E_(2g)^(2)(in-plane)and A_(1g)(out-of-plane)Raman modes,respectively.Moreover,the Mn dopants increase the valley Zeeman splitting of the MoSe_(2) monolayer by~50%,while preserving the linear dependence on magnetic field.First-principles calculations indicate that the spin-polarized deep level defect states are formed due to the Mn substitutional dopants in the Mo Se_(2) lattice.The resulting defect potential favors the funnelling of excitons towards the defects.The Mn dopants reduce the magnitude of the interatomic force constants,explaining the red-shift of the A_(1g)mode.The Mn atoms and their immediate Mo and Se neighbors carry significant magnetic moments,which enhance the observed exciton g-factors due to the exchange interactions affecting defect-bound excitons.展开更多
基金the Singapore National Research Foundation through the NRF Investigatorship Award(No.NRF-NRFI2015-03)the Singapore Ministry of Education via AcRF Tier 3 Programme(No.MOE2018-T3-1-002),Tier 2 grant(No.MOE2018-T2-2-068)and Tier 1 grants(Nos.RG103/15 and RG113/16)A.G.D.A.gratefully acknowledges the financial support of the Presidential Postdoctoral Fellowship program of the Nanyang Technological University
文摘Up-conversion photoluminescence(UCPL)refers to the elementary process where low-energy photons are converted into high-energy ones via consecutive interactions inside a medium.When additional energy is provided by intermnal thermal energy in the form of lttice vibrations(phonons),the process is called phonon-assisted UCPL.Here,we report the exceptionally large phonon-assisted energy gain of up to^8kgT(kg is Boltzmann constant,T is temperature)on all-inorganic lead halide perovskite semiconductor colloidal nanocrystals that goes beyond the maximum capabilty of only harvesting optical phonon modes.By systematic optical study in combination with a statistical probability model,we explained the nontrivial phonon-assisted UCPL process in perovskites nanocrystals,where in addition to the strong electron-phonon(light-matter)coupling,other nonlinear processes such as phonon-phonon(matter-matter)interaction also effectively boost the up-conversion efficiency.
基金support from Singapore Ministry of Education via Ac RF Tier3 Programme“Geometrical Quantum Materials”(MOE2018-T3-1-002),Ac RF Tier2 grant(MOE2017-T2-1-040)and Tier1 grant(RG 194/17)funding from the National Research Foundation,Prime Ministers Office,Singapore,under its Medium-Sized Centre Programmethe funding from MOE2017-T2-2-139。
文摘Introducing magnetic dopants into twodimensional transition metal dichalcogenides has recently attracted considerable attention due to its promising applications in spintronics and valleytronics.Herein we realized manganese-doped molybdenum diselenide(MoSe_(2))single crystal via chemical vapor transport(CVT)reaction,containing up to 2.9%(atomic concentration)Mn dopants,and investigated the light-matter interaction in these samples.We observed a suppressed trion intensity,a longer photoluminescence lifetime,and prominent blue-and red-shift of E_(2g)^(2)(in-plane)and A_(1g)(out-of-plane)Raman modes,respectively.Moreover,the Mn dopants increase the valley Zeeman splitting of the MoSe_(2) monolayer by~50%,while preserving the linear dependence on magnetic field.First-principles calculations indicate that the spin-polarized deep level defect states are formed due to the Mn substitutional dopants in the Mo Se_(2) lattice.The resulting defect potential favors the funnelling of excitons towards the defects.The Mn dopants reduce the magnitude of the interatomic force constants,explaining the red-shift of the A_(1g)mode.The Mn atoms and their immediate Mo and Se neighbors carry significant magnetic moments,which enhance the observed exciton g-factors due to the exchange interactions affecting defect-bound excitons.
