In the framework of the tight-binding model, the excitons states and linear absorption spectra are calculated in the metallic single-walled carbon nanotubes, with the axial magnetic field applied. From our calculation...In the framework of the tight-binding model, the excitons states and linear absorption spectra are calculated in the metallic single-walled carbon nanotubes, with the axial magnetic field applied. From our calculations, it is found that for the Mll and M22 transitions, the exeiton states are split into four separate column states by the applied magnetic field due to the symmetry breaking. More interesting is that the splitting can be directly reflected from the linear absorption spectra~ which are dominated by four main absorption peaks. In addition, the splitting with increasing the axial magnetic field is also calculated, which increases linearly with the applied magnetic field. The obtained results are expected to be detected by the future experiments.展开更多
The goal of this paper is to show that there are infinitely many number fields K/Q, for which there is no inert prime p ∈ N*, i.e. ∀p ∈ N* a prime number, prime ideal of K such that where: Zk</sub> i...The goal of this paper is to show that there are infinitely many number fields K/Q, for which there is no inert prime p ∈ N*, i.e. ∀p ∈ N* a prime number, prime ideal of K such that where: Zk</sub> is the Dedekind domain of the integer elements of K. To prove such a result, consider for any prime p, the decomposition into a product of prime ideals of Zk</sub>, of the ideal . From this point, we use on the one hand: 1) The well- known property that says: If , then the ideal pZ<sub>k</sub> decomposes into a product of prime ideals of Zk</sub> as following: . (where:;is the irreducible polynomial of θ, and, is its reduction modulo p, which leads to a product of irreducible polynomials in Fp[X]). It is clear that because if is reducible in Fp[X], then consequently p is not inert. Now, we prove the existence of such p, by proving explicit such p as follows. So we use on the other hand: 2) this property that we prove, and which is: If , is an irreducible normalized integer polynomial, whose splitting field is , then for any prime number p ∈ N: is always a reducible polynomial. 3) Consequently, and this closes our proof: let’s consider the set (whose cardinality is infinite) of monogenic biquadratic number fields: . Then each f<sub>θ</sub>(X) checks the above properties, this means that for family M, all its fields, do not admit any inert prime numbers p ∈ N. 2020-Mathematics Subject Classification (MSC2020) 11A41 - 11A51 - 11D25 - 11R04 - 11R09 - 11R11 - 11R16 - 11R32 - 11T06 - 12E05 - 12F05 -12F10 -13A05-13A15 - 13B02 - 13B05 - 13B10 - 13B25 -13F05展开更多
A series of single-phased Ca2Al2SiOT：EU2＋phosphors were synthesized by the solid-state reaction. Their structure and photoluminescence properties were investigated by the X-ray powder diffraction （XRD） and excitat...A series of single-phased Ca2Al2SiOT：EU2＋phosphors were synthesized by the solid-state reaction. Their structure and photoluminescence properties were investigated by the X-ray powder diffraction （XRD） and excitation and emission spectra in detail. The emission spectra of Ca2Al2SiO7：Eu2＋ phosphors consisted of blue and green band located at 419 and 542 nm, respectively. The relative intensities of the blue and green emission changed with Eu2＋ concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f^7→4f65d transition of Eu2＋ at different energy levels, on which the effect of the crystal field strength was con- sidered to be tailed by adjusting the host composition.展开更多
The electron-phonon(el-ph)and phonon-phonon interactions play a key role in determining electronic and thermal transport properties,respectively,in promising two-dimensional(2D)semiconductor de-vices.In this study,we ...The electron-phonon(el-ph)and phonon-phonon interactions play a key role in determining electronic and thermal transport properties,respectively,in promising two-dimensional(2D)semiconductor de-vices.In this study,we investigated el-ph interactions using Wannier-Fourier interpolation method and renormalized phonon scattering considering finite-temperature effects in Bi_(2)TeSe_(2)monolayer.The re-sults show that the optical phonon modes dominate the carrier scattering,where level repulsion induced by crystal field splitting and spin-orbit coupling(SOC)effect effectively suppresses intervalley scattering,leading to high hole mobility.Moreover,the strong anharmonicity in Bi_(2)TeSe_(2)monolayer results in the temperature-dependent softening of its optical phonons,along with a corresponding variation in interatomic force constants(IFCs).As a result,the lattice thermal conductivity is remarkably low and exhibits weak temperature dependence.Finally,the predicted dimensionless thermoelectric figure of merit exceeds unity in the range of 200-800 K,indicating the potential of Bi_(2)TeSe_(2)monolayer for thermoelectric applications.This work provides new insights into the elimination of intervalley scat-tering by crystal field splitting and SOC effects,and paves the way for the evaluation of thermoelectric properties of materials with complex scattering mechanisms and strong anharmonicity.展开更多
α-RuCl_(3)is a tantalizing playground to search for the quantum spin liquid states with leading Kitaev term due to the conformation of Jackeli-Khaliullin mechanism.Suppressing the non-Kitaev interaction to approach t...α-RuCl_(3)is a tantalizing playground to search for the quantum spin liquid states with leading Kitaev term due to the conformation of Jackeli-Khaliullin mechanism.Suppressing the non-Kitaev interaction to approach the Kitaev limit is the major objective in the experimental design of Kitaev-Jackeli-Khaliullin materials,for which the practical feasibility rests on the manipulation of the exact crystalline structure.A tensile strain,leading to the further compressive trigonal field splitting which would alter the spin-orbital entangled character and tune the intrinsic hopping exchanges,has been widely proposed as the promising strategy to enhance the comparative Kitaev interaction.In this work,we preform in-depth Scan Tunneling Microscope study on the electronic patterns of strainedα-RuCl_(3)monolayer on graphite substrate.Based on Chen’s derivative rule,a further trigonal field splitting is identified by analyzing the lateral-gradient imaging effect caused by an anisotropic tip.A spatial variation of the magnitude of trigonal crystal field due to the slight inhomogeneity of strain accords with the orbital polarization near the Mott gap.All evidences point to the facts that the compressive trigonal crystal field in the stretchedα-RuCl_(3)monolayer lifts the degeneracy of t2g states with higher eg and lower a1g orbitals,and the Coulomb interactions of the eg orbitals take the main responsibility for the Mott effect.展开更多
Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties...Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties are poor.Here,the thermoelectric performance of Mg_(3)Sb_(2) under the effect of biaxial strain is investigated by using first-principles method and Boltzmann transport theory.The application of biaxial strain enables tuning the band structure of Mg_(3)Sb_(2) in such a way that the band degeneracy of both the conduction band and valence band increases.As the biaxial strain increases,the Seebeck coefficient of ptype Mg_(3)Sb_(2) has a remarkable increase,leading to a significant improvement in power factor.This is mainly ascribed to the achievement of valence band orbital degeneracy.Meanwhile,the lattice thermal conductivity exhibits very slight biaxial strain dependence within the strain range considered in this work,which increases from 1.28 to 1.62 W m^(-1) K^(-1) at 300 K.Finally,the highest ZT of p-type Mg_(3)Sb_(2) at 700 K can be up to 2.6 along the in-plane direction under-2.5%biaxial strain,which is almost three times that of the unstrained counterpart.The realization of high thermoelectric performance of p-type Mg_(3)Sb_(2) will promote its practical applications as thermoelectric generators.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11304378 and 11304377the Fundamental Research Funds for the Central Universities under Grant No 2013QNA42
文摘In the framework of the tight-binding model, the excitons states and linear absorption spectra are calculated in the metallic single-walled carbon nanotubes, with the axial magnetic field applied. From our calculations, it is found that for the Mll and M22 transitions, the exeiton states are split into four separate column states by the applied magnetic field due to the symmetry breaking. More interesting is that the splitting can be directly reflected from the linear absorption spectra~ which are dominated by four main absorption peaks. In addition, the splitting with increasing the axial magnetic field is also calculated, which increases linearly with the applied magnetic field. The obtained results are expected to be detected by the future experiments.
文摘The goal of this paper is to show that there are infinitely many number fields K/Q, for which there is no inert prime p ∈ N*, i.e. ∀p ∈ N* a prime number, prime ideal of K such that where: Zk</sub> is the Dedekind domain of the integer elements of K. To prove such a result, consider for any prime p, the decomposition into a product of prime ideals of Zk</sub>, of the ideal . From this point, we use on the one hand: 1) The well- known property that says: If , then the ideal pZ<sub>k</sub> decomposes into a product of prime ideals of Zk</sub> as following: . (where:;is the irreducible polynomial of θ, and, is its reduction modulo p, which leads to a product of irreducible polynomials in Fp[X]). It is clear that because if is reducible in Fp[X], then consequently p is not inert. Now, we prove the existence of such p, by proving explicit such p as follows. So we use on the other hand: 2) this property that we prove, and which is: If , is an irreducible normalized integer polynomial, whose splitting field is , then for any prime number p ∈ N: is always a reducible polynomial. 3) Consequently, and this closes our proof: let’s consider the set (whose cardinality is infinite) of monogenic biquadratic number fields: . Then each f<sub>θ</sub>(X) checks the above properties, this means that for family M, all its fields, do not admit any inert prime numbers p ∈ N. 2020-Mathematics Subject Classification (MSC2020) 11A41 - 11A51 - 11D25 - 11R04 - 11R09 - 11R11 - 11R16 - 11R32 - 11T06 - 12E05 - 12F05 -12F10 -13A05-13A15 - 13B02 - 13B05 - 13B10 - 13B25 -13F05
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (20115314120001) the Special Program for National Program on Key Basic Research Project of China (973 Program) (2011CB211708) the Foundation of Natural Science of Yunnan Province (2011FB022)
文摘A series of single-phased Ca2Al2SiOT：EU2＋phosphors were synthesized by the solid-state reaction. Their structure and photoluminescence properties were investigated by the X-ray powder diffraction （XRD） and excitation and emission spectra in detail. The emission spectra of Ca2Al2SiO7：Eu2＋ phosphors consisted of blue and green band located at 419 and 542 nm, respectively. The relative intensities of the blue and green emission changed with Eu2＋ concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f^7→4f65d transition of Eu2＋ at different energy levels, on which the effect of the crystal field strength was con- sidered to be tailed by adjusting the host composition.
基金supported by the National Natural Science Foundation of China(62275053,61775042,11674062,11374063)Shanghai Municipal Natural Science Foundation under Grant Nos.19ZR1402900 and the Fudan University-CIOMP Joint Fund(FC2017-003).
文摘The electron-phonon(el-ph)and phonon-phonon interactions play a key role in determining electronic and thermal transport properties,respectively,in promising two-dimensional(2D)semiconductor de-vices.In this study,we investigated el-ph interactions using Wannier-Fourier interpolation method and renormalized phonon scattering considering finite-temperature effects in Bi_(2)TeSe_(2)monolayer.The re-sults show that the optical phonon modes dominate the carrier scattering,where level repulsion induced by crystal field splitting and spin-orbit coupling(SOC)effect effectively suppresses intervalley scattering,leading to high hole mobility.Moreover,the strong anharmonicity in Bi_(2)TeSe_(2)monolayer results in the temperature-dependent softening of its optical phonons,along with a corresponding variation in interatomic force constants(IFCs).As a result,the lattice thermal conductivity is remarkably low and exhibits weak temperature dependence.Finally,the predicted dimensionless thermoelectric figure of merit exceeds unity in the range of 200-800 K,indicating the potential of Bi_(2)TeSe_(2)monolayer for thermoelectric applications.This work provides new insights into the elimination of intervalley scat-tering by crystal field splitting and SOC effects,and paves the way for the evaluation of thermoelectric properties of materials with complex scattering mechanisms and strong anharmonicity.
基金the National Key Research and Development Program of China(Grant No.2019YFA0308404)Science and Technology Commission of Shanghai Municipality(Grant No.20JC1415900)+3 种基金Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)support from the National Natural Science Foundation of China(Grants No.12174062)sponsored by Shanghai Pujiang Program No.19PJ1401000National Natural Science Foundation of China(Grant No.12004076).
文摘α-RuCl_(3)is a tantalizing playground to search for the quantum spin liquid states with leading Kitaev term due to the conformation of Jackeli-Khaliullin mechanism.Suppressing the non-Kitaev interaction to approach the Kitaev limit is the major objective in the experimental design of Kitaev-Jackeli-Khaliullin materials,for which the practical feasibility rests on the manipulation of the exact crystalline structure.A tensile strain,leading to the further compressive trigonal field splitting which would alter the spin-orbital entangled character and tune the intrinsic hopping exchanges,has been widely proposed as the promising strategy to enhance the comparative Kitaev interaction.In this work,we preform in-depth Scan Tunneling Microscope study on the electronic patterns of strainedα-RuCl_(3)monolayer on graphite substrate.Based on Chen’s derivative rule,a further trigonal field splitting is identified by analyzing the lateral-gradient imaging effect caused by an anisotropic tip.A spatial variation of the magnitude of trigonal crystal field due to the slight inhomogeneity of strain accords with the orbital polarization near the Mott gap.All evidences point to the facts that the compressive trigonal crystal field in the stretchedα-RuCl_(3)monolayer lifts the degeneracy of t2g states with higher eg and lower a1g orbitals,and the Coulomb interactions of the eg orbitals take the main responsibility for the Mott effect.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.11775163,12175166,12175079the National Key R&D Program of China(2019YFA0210003).
文摘Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties are poor.Here,the thermoelectric performance of Mg_(3)Sb_(2) under the effect of biaxial strain is investigated by using first-principles method and Boltzmann transport theory.The application of biaxial strain enables tuning the band structure of Mg_(3)Sb_(2) in such a way that the band degeneracy of both the conduction band and valence band increases.As the biaxial strain increases,the Seebeck coefficient of ptype Mg_(3)Sb_(2) has a remarkable increase,leading to a significant improvement in power factor.This is mainly ascribed to the achievement of valence band orbital degeneracy.Meanwhile,the lattice thermal conductivity exhibits very slight biaxial strain dependence within the strain range considered in this work,which increases from 1.28 to 1.62 W m^(-1) K^(-1) at 300 K.Finally,the highest ZT of p-type Mg_(3)Sb_(2) at 700 K can be up to 2.6 along the in-plane direction under-2.5%biaxial strain,which is almost three times that of the unstrained counterpart.The realization of high thermoelectric performance of p-type Mg_(3)Sb_(2) will promote its practical applications as thermoelectric generators.
