We report the ultrafast optical pump-probe spectroscopy measurements on the single-crystal cerium films.Our experimental results of temperature-dependent quasiparticle dynamics reveal development of the hybridization ...We report the ultrafast optical pump-probe spectroscopy measurements on the single-crystal cerium films.Our experimental results of temperature-dependent quasiparticle dynamics reveal development of the hybridization between localized f moments and conduction electrons,i.e.,evolving from fluctuating hybridization to collective hybridization.Exotic phonon renormalization is discovered to appear at the emerging temperature(T^(+))of fluctuating hybridization apart from its known presence at the coherent temperature(T^(*)),and can hardly be explained by the mean-field theory.The quasiparticle relaxation at high temperatures indicates coexistence of nonthermal electron-electron scattering and inelastic Kondo scattering,while its behavior at low temperatures suggests onset ofαphase in theγ-phase dominated film.We also extract the indirect gap below T^(*),representing the appearance of collective hybridization.Our findings provide novel information about the hybridization and phase evolution in the heavy fermion systems.展开更多
Mottness is at the heart of the essential physics in a strongly correlated system as many novel quantum phenomena occur in the metallic phase near the Mott metal–insulator transition. We investigate the Mott transiti...Mottness is at the heart of the essential physics in a strongly correlated system as many novel quantum phenomena occur in the metallic phase near the Mott metal–insulator transition. We investigate the Mott transition in a Hubbard model by using the dynamical mean-field theory and introduce the local quantum state fidelity to depict the Mott metal–insulator transition. The local quantum state fidelity provides a convenient approach to determining the critical point of the Mott transition. Additionally, it presents a consistent description of the two distinct forms of the Mott transition points.展开更多
The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase...The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes.Here,we have fabricated and measured Al-InSb nanowire quantum dot-Al devices.In the Kondo regime,a supercurrent-induced zero-bias conductance peak emerges.This zero-bias peak shows an anomalous negative magnetoresistance(NMR)at weak magnetic fields.We attribute this anomalous NMR to quasiparticle trapping at vortices in the superconductor leads as a weak magnetic field is applied.The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current.This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.展开更多
The quasiparticle resonances are investigated by examining three kinds of quasiparticle spectra, i.e., the density of quasiparticle states, the occupation number density, and the pair number density in the continuum S...The quasiparticle resonances are investigated by examining three kinds of quasiparticle spectra, i.e., the density of quasiparticle states, the occupation number density, and the pair number density in the continuum Skyrme Hartree-Fock-Bogoliubov theory with the Green’s function method. Taking the weakly bound nucleus 66Ca as an example, the quasiparticle resonant energies and widths extracted from these three kinds of quasiparticle spectra are compared. For the narrow resonances, the extracted resonant energy and the width are consistent with each other. However, it is difficult to use the density of quasiparticle states to identify the broad resonances due to the background of nonresonant continuum. By switching off the pairing potential and/or the Hartree-Fock(HF) potential respectively in the calculation of these quasiparticle spectra, the roles of HF mean-field and pairing correlations in the quasiparticle resonances are demonstrated clearly. It turns out that all the quasiparticle resonances corresponding to the deeply bound, weakly bound and positive-energy single-particle resonant states, are mainly contributed by the HF potential. The pairing potential helps to slightly increase the resonant energy and the width. However, the pairing potential is important to make the nucleons occupy the low-lying nonresonant continuum states near the threshold and take part in the pairing correlations here,especially for the partial waves with small angular momentum ?.展开更多
Excited states of the positive-parity intruder band in 11SSn have been studied via the ^116Cd（^7Li, 1p4n） reaction at ^7Li energy of 48 MeV using techniques of in-beam y-ray spectroscopy. This intruder band has been...Excited states of the positive-parity intruder band in 11SSn have been studied via the ^116Cd（^7Li, 1p4n） reaction at ^7Li energy of 48 MeV using techniques of in-beam y-ray spectroscopy. This intruder band has been observed up to ^7187 keV with spin （16^＋）. The structural evolution of this intruder band with increasing angular momentum has been discussed in terms of the aligned angular momentum and the ratio of the E-Gamma Over Spin （E-COS） curve.展开更多
Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenome...Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.展开更多
The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected...The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.展开更多
A tentative method based on the principle of minimum energy is put forward for assigning the reasonable configuration of a triaxial nucleus in TRS. This method is proved by the TSD of 167Lu nucleus that has been calcu...A tentative method based on the principle of minimum energy is put forward for assigning the reasonable configuration of a triaxial nucleus in TRS. This method is proved by the TSD of 167Lu nucleus that has been calculated previously by TRS.展开更多
Dynamics of domain walls(DWs) was studied in transparent thin orthoferrite samples with weak ferromagnetic ordering at subsonic and supersonic speeds.Direct measurements were made of flexural vibration amplitude in th...Dynamics of domain walls(DWs) was studied in transparent thin orthoferrite samples with weak ferromagnetic ordering at subsonic and supersonic speeds.Direct measurements were made of flexural vibration amplitude in the samples studied,which were induced by a solitary DW with periodic actions of a driving magnetic field.The values of the amplitude reached 7 nm at a resonance.The formation of magnetoelastic solitons was observed and their dynamics was studied at a resonance between an elastic and a spin subsystems.Solitons lag behind the DW at the moment when the DW surpasses the sound barrier and are ahead of it at the subsonic motion.展开更多
-The calculation method for the transitional odd-A nuclei is studied.The theo-retical calculation of the energy level structure of <sup>147</sup>pm and <sup>149</sup>EU is performed bycoupling ...-The calculation method for the transitional odd-A nuclei is studied.The theo-retical calculation of the energy level structure of <sup>147</sup>pm and <sup>149</sup>EU is performed bycoupling the 1+3 quasiparticles to the anharmonic vibration of the core.Aparticle-number-conservation treatment is made by means of the projection method.The effects of the particle-number projection,the three-d-boson excitation and residualinteraction on the lower excited states are discussed.展开更多
The low-lying electric dipole strengths in proton-rich nuclei 17F and 17Ne, which can be produced at HIRFL-CSR in Lanzhou, are investigated. In the framework of the covariant density functional theory the self-consist...The low-lying electric dipole strengths in proton-rich nuclei 17F and 17Ne, which can be produced at HIRFL-CSR in Lanzhou, are investigated. In the framework of the covariant density functional theory the self-consistent relativistic Hartree Bogoliubov model and the relativistic quasiparticle random phase approximation with the NL3 parameter set and Gogny pairing interaction are adopted in the calculations. A pronounced dipole peak appears below 10 MeV in17Ne, but does not occur in 17F. The prop erties of this low-lying E1 excitation in 17Ne are studied, which may correspond to a proton pygmy resonance with different characteristics from those of giant dipole resonance.展开更多
Specific heat is a powerful tool to investigate the physical properties of condensed materials.Superconducting state is achieved through the condensation of paired electrons,namely,the Cooper pairs.The condensed Coope...Specific heat is a powerful tool to investigate the physical properties of condensed materials.Superconducting state is achieved through the condensation of paired electrons,namely,the Cooper pairs.The condensed Cooper pairs have lower entropy compared with that of electrons in normal metal,thus specific heat is very useful in detecting the low lying quasiparticle excitations of the superconducting condensate and the pairing symmetry of the superconducting gap.In this brief overview,we will give an introduction to the specific heat investigation of the physical properties of superconductors.We show the data obtained in cuprate and iron based superconductors to reveal the pairing symmetry of the order parameter.展开更多
Using the extended Blonder-Tinkham-Klapwijk （BTK） theory, this paper calculates the tunnelling conductance in quantum wire/insulator/dx2-y2 ＋ idly mixed wave superconductor （q/I/dx2-y2 ＋ idly） junctions. That is...Using the extended Blonder-Tinkham-Klapwijk （BTK） theory, this paper calculates the tunnelling conductance in quantum wire/insulator/dx2-y2 ＋ idly mixed wave superconductor （q/I/dx2-y2 ＋ idly） junctions. That is different from the case in d- and p-wave superconductor junctions. When the angle α between a-axis of the dx2-y2 wave superconductor and the interface normal is π/4, there follows a rather distinctive tunnelling conductance. The zero-bias conductance peak （ZBCP） may or may not appear in the tunnelling conductance. Both the interface potential z and the quasi-particle lifetime factor F are smaller, there is no ZBCP. Otherwise, the ZBCP will appear. The position of bias conductance peak （BCP） depends strongly on the amplitude ratio of two components for dx2-y2 ＋ idxy mixed wave. The low and narrow ZBCP may coexist with the BCP in the tunnelling conductance. Using those features in the tunnelling conductance of q/I/dx2-y2 ＋ idxy junctions, it can distinguish dx2-y2 ＋ idxy mixed wave superconductor from d- and p-wave one.展开更多
We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent osc...We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent oscillations having extremely low energies of hω_(1)~0.33 me V(0.08 THz)and hω_(2)-1.9 me V(0.45 THz),which are softened as the temperature approaches two different critical temperatures(~54 K and~135 K).We attribute these two collective excitations to the amplitude mode of photoinduced dynamic charge density waves in ZrTe_(5) with tremendously small nesting wave vectors.Furthermore,a peculiar quasiparticle decay process associated with the hω_(2) mode with a timescale of~1-2 ps is found below the transition temperature T*(~135 K).Our findings provide pivotal information for studying the fluctuating order parameters and their associated quasiparticle dynamics in various low-dimensional topological systems and other materials.展开更多
Polyyne,an sp~1-hybridized linear allotrope of carbon,has a tunable quasiparticle energy gap,which depends on the terminated chemical ending groups as well as the chain length.Previously,nitrogen doping was utilized t...Polyyne,an sp~1-hybridized linear allotrope of carbon,has a tunable quasiparticle energy gap,which depends on the terminated chemical ending groups as well as the chain length.Previously,nitrogen doping was utilized to tailor the properties of different kinds of allotrope of carbon.However,how the nitrogen doping tailors the properties of the polyyne remains unexplored.Here,we applied the GW method to study the quasiparticle energy gaps of the N-doped polyynes with different lengths.When a C atom is substituted by an N atom in a polyyne,the quasiparticle energy gap varies with the substituted position in the polyyne.The modification is particularly pronounced when the second-nearest-neighboring carbon atom of a hydrogen atom is substituted.In addition,the nitrogen doping makes the Fermi level closer to the lowest unoccupied molecular orbital,resulting in an n-type semiconductor.Our results suggest another route to tailor the electronic properties of polyyne in addition to the length of polyyne and the terminated chemical ending groups.展开更多
We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual interaction.Both particle-hole and parti...We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual interaction.Both particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix equation.The sensitivity of the calculated half-lives to some physical quantities used in the calculations is examined.Calculations are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = 76.Good agreement between experiment and theory is achieved especially for the nuclei far from stability,and the results of our calculations are discussed with comparison with other theoretical results.Predictions on the β-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.展开更多
Defect levels in semiconductor band gaps play a crucial role in functionalized semiconductors for practical applications in optoelectronics;however,first-principle defect calculations based on exchange-correlation fun...Defect levels in semiconductor band gaps play a crucial role in functionalized semiconductors for practical applications in optoelectronics;however,first-principle defect calculations based on exchange-correlation functionals,such as local density approximation,grand gradient approximation(GGA),and hybrid functionals,either underestimate band gaps or misplace defect levels.In this study,we revisited iodine defects in CH_(3)NH_(3)PbI_(3) by combining the accuracy of total energy calculations of GGA and single-electron level calculation of the GW method.The combined approach predicted neutral Im_(i) to be unstable and the transition level of Im_(i)(+1/-1)to be close to the valence band maximum.Therefore,Im_(i) may not be as detrimental as previously reported.Moreover,Vm I may be unstable in the-1 charged state but could still be detrimental owing to the deep transition level of Vm I(+1/0).These results could facilitate the further understanding of the intrinsic point defect and defect passivation observed in CH_(3)NH_(3)PbI_(3).展开更多
We study the behaviors of three-dimensional double and triple Weyl fermions in the presence of weak random potential.By performing the Wilsonian renormalization group(RG)analysis,we reveal that the quasiparticle exper...We study the behaviors of three-dimensional double and triple Weyl fermions in the presence of weak random potential.By performing the Wilsonian renormalization group(RG)analysis,we reveal that the quasiparticle experiences strong renormalization which leads to the modification of the density of states and quasiparticle residue.We further utilize the RG analysis to calculate the classical conductivity and show that the diffusive transport is substantially corrected due to the novel behavior of the quasiparticle and can be directly measured by experiments.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403000,and 2022YFA1402200)the National Natural Science Foundation of China(Grant Nos.92365102,11974070,11734006,11925408,11921004,12004067,62027807,and 12174331)the Frontier Science Project of Dongguan(Grant No.2019622101004)。
文摘We report the ultrafast optical pump-probe spectroscopy measurements on the single-crystal cerium films.Our experimental results of temperature-dependent quasiparticle dynamics reveal development of the hybridization between localized f moments and conduction electrons,i.e.,evolving from fluctuating hybridization to collective hybridization.Exotic phonon renormalization is discovered to appear at the emerging temperature(T^(+))of fluctuating hybridization apart from its known presence at the coherent temperature(T^(*)),and can hardly be explained by the mean-field theory.The quasiparticle relaxation at high temperatures indicates coexistence of nonthermal electron-electron scattering and inelastic Kondo scattering,while its behavior at low temperatures suggests onset ofαphase in theγ-phase dominated film.We also extract the indirect gap below T^(*),representing the appearance of collective hybridization.Our findings provide novel information about the hybridization and phase evolution in the heavy fermion systems.
基金Project supported by the Scientific Research Foundation for Youth Academic Talent of Inner Mongolia University (Grant No.1000023112101/010)the Fundamental Research Funds for the Central Universities of China (Grant No.JN200208)+2 种基金supported by the National Natural Science Foundation of China (Grant No.11474023)supported by the National Key Research and Development Program of China (Grant No.2021YFA1401803)the National Natural Science Foundation of China (Grant Nos.11974051 and 11734002)。
文摘Mottness is at the heart of the essential physics in a strongly correlated system as many novel quantum phenomena occur in the metallic phase near the Mott metal–insulator transition. We investigate the Mott transition in a Hubbard model by using the dynamical mean-field theory and introduce the local quantum state fidelity to depict the Mott metal–insulator transition. The local quantum state fidelity provides a convenient approach to determining the critical point of the Mott transition. Additionally, it presents a consistent description of the two distinct forms of the Mott transition points.
基金supported by the Swedish Research Council(VR)the National Natural Science Foundation of China(Grant Nos.92165208,11874071,91221202,91421303,and 11904399)+7 种基金the National Key Research and Development Program of China(Grant Nos.2016YFA0300601,and 2017YFA0303304)Beijing Academy of Quantum Information Sciences(Grant No.Y18G22)the financial supports by Hunan Provincial Science Foundation for Distinguished Young Scholars(Grant No.2021JJ10043)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302401)the financial support by the Spanish Ministry of Economy and Competitiveness(Grant No.PID2020-117347GBI00)the financial supports by the Spanish Ministry of Economy and Competitiveness(Grant No.PID2020-11778GB-I00)the Mara de Maeztu project CEX2021-001164-M funded by the MCIN/AEI/10.13039/501100011033the supports from CSIC Research Platform PTI-001 and through the grant LINKB20072(CSIC)。
文摘The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes.Here,we have fabricated and measured Al-InSb nanowire quantum dot-Al devices.In the Kondo regime,a supercurrent-induced zero-bias conductance peak emerges.This zero-bias peak shows an anomalous negative magnetoresistance(NMR)at weak magnetic fields.We attribute this anomalous NMR to quasiparticle trapping at vortices in the superconductor leads as a weak magnetic field is applied.The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current.This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0404400)the National Natural Science Foundation of China(Grant Nos.11621131001,11405116,and 11875075)
文摘The quasiparticle resonances are investigated by examining three kinds of quasiparticle spectra, i.e., the density of quasiparticle states, the occupation number density, and the pair number density in the continuum Skyrme Hartree-Fock-Bogoliubov theory with the Green’s function method. Taking the weakly bound nucleus 66Ca as an example, the quasiparticle resonant energies and widths extracted from these three kinds of quasiparticle spectra are compared. For the narrow resonances, the extracted resonant energy and the width are consistent with each other. However, it is difficult to use the density of quasiparticle states to identify the broad resonances due to the background of nonresonant continuum. By switching off the pairing potential and/or the Hartree-Fock(HF) potential respectively in the calculation of these quasiparticle spectra, the roles of HF mean-field and pairing correlations in the quasiparticle resonances are demonstrated clearly. It turns out that all the quasiparticle resonances corresponding to the deeply bound, weakly bound and positive-energy single-particle resonant states, are mainly contributed by the HF potential. The pairing potential helps to slightly increase the resonant energy and the width. However, the pairing potential is important to make the nucleons occupy the low-lying nonresonant continuum states near the threshold and take part in the pairing correlations here,especially for the partial waves with small angular momentum ?.
基金Supported by National Natural Science Foundation of China (10875074, 10605001, 10505002, 10775005)Major StateBasic Research Developing Program (2007CB815005)
文摘Excited states of the positive-parity intruder band in 11SSn have been studied via the ^116Cd（^7Li, 1p4n） reaction at ^7Li energy of 48 MeV using techniques of in-beam y-ray spectroscopy. This intruder band has been observed up to ^7187 keV with spin （16^＋）. The structural evolution of this intruder band with increasing angular momentum has been discussed in terms of the aligned angular momentum and the ratio of the E-Gamma Over Spin （E-COS） curve.
文摘Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.
基金Supported by National Natural Science Foundation of China(U1632137)
文摘The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.
基金Supported by National Basic Research Program of China (2007CB815005)National Natural Science Foundation of China(11075064,11165001,10975051)Specialized Research Fund for the Doctoral Program of Higher Education of China(20050183008)
文摘A tentative method based on the principle of minimum energy is put forward for assigning the reasonable configuration of a triaxial nucleus in TRS. This method is proved by the TSD of 167Lu nucleus that has been calculated previously by TRS.
文摘Dynamics of domain walls(DWs) was studied in transparent thin orthoferrite samples with weak ferromagnetic ordering at subsonic and supersonic speeds.Direct measurements were made of flexural vibration amplitude in the samples studied,which were induced by a solitary DW with periodic actions of a driving magnetic field.The values of the amplitude reached 7 nm at a resonance.The formation of magnetoelastic solitons was observed and their dynamics was studied at a resonance between an elastic and a spin subsystems.Solitons lag behind the DW at the moment when the DW surpasses the sound barrier and are ahead of it at the subsonic motion.
基金The project supported in part by National Natural Science Foundation of China and by the Grant LWTZ 1298 of Academia Sinica.
文摘-The calculation method for the transitional odd-A nuclei is studied.The theo-retical calculation of the energy level structure of <sup>147</sup>pm and <sup>149</sup>EU is performed bycoupling the 1+3 quasiparticles to the anharmonic vibration of the core.Aparticle-number-conservation treatment is made by means of the projection method.The effects of the particle-number projection,the three-d-boson excitation and residualinteraction on the lower excited states are discussed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10775183, 10875150 and 11075213)the National Basic Research Program of China (Grant No. 2007CB815000)
文摘The low-lying electric dipole strengths in proton-rich nuclei 17F and 17Ne, which can be produced at HIRFL-CSR in Lanzhou, are investigated. In the framework of the covariant density functional theory the self-consistent relativistic Hartree Bogoliubov model and the relativistic quasiparticle random phase approximation with the NL3 parameter set and Gogny pairing interaction are adopted in the calculations. A pronounced dipole peak appears below 10 MeV in17Ne, but does not occur in 17F. The prop erties of this low-lying E1 excitation in 17Ne are studied, which may correspond to a proton pygmy resonance with different characteristics from those of giant dipole resonance.
文摘Specific heat is a powerful tool to investigate the physical properties of condensed materials.Superconducting state is achieved through the condensation of paired electrons,namely,the Cooper pairs.The condensed Cooper pairs have lower entropy compared with that of electrons in normal metal,thus specific heat is very useful in detecting the low lying quasiparticle excitations of the superconducting condensate and the pairing symmetry of the superconducting gap.In this brief overview,we will give an introduction to the specific heat investigation of the physical properties of superconductors.We show the data obtained in cuprate and iron based superconductors to reveal the pairing symmetry of the order parameter.
文摘Using the extended Blonder-Tinkham-Klapwijk （BTK） theory, this paper calculates the tunnelling conductance in quantum wire/insulator/dx2-y2 ＋ idly mixed wave superconductor （q/I/dx2-y2 ＋ idly） junctions. That is different from the case in d- and p-wave superconductor junctions. When the angle α between a-axis of the dx2-y2 wave superconductor and the interface normal is π/4, there follows a rather distinctive tunnelling conductance. The zero-bias conductance peak （ZBCP） may or may not appear in the tunnelling conductance. Both the interface potential z and the quasi-particle lifetime factor F are smaller, there is no ZBCP. Otherwise, the ZBCP will appear. The position of bias conductance peak （BCP） depends strongly on the amplitude ratio of two components for dx2-y2 ＋ idxy mixed wave. The low and narrow ZBCP may coexist with the BCP in the tunnelling conductance. Using those features in the tunnelling conductance of q/I/dx2-y2 ＋ idxy junctions, it can distinguish dx2-y2 ＋ idxy mixed wave superconductor from d- and p-wave one.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974070,11734006,11925408,and 11921004)the Frontier Science Project of Dongguan(Grant No.2019622101004)+5 种基金the National Key R&D Program of China(Grant Nos.2016YFA0300600,and 2018YFA0305700)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the Beijing Natural Science Foundation(Grant No.Z180008)the Beijing Municipal Science and Technology Commission(Grant No.Z191100007219013)the CAS Interdisciplinary Innovation Team。
文摘We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent oscillations having extremely low energies of hω_(1)~0.33 me V(0.08 THz)and hω_(2)-1.9 me V(0.45 THz),which are softened as the temperature approaches two different critical temperatures(~54 K and~135 K).We attribute these two collective excitations to the amplitude mode of photoinduced dynamic charge density waves in ZrTe_(5) with tremendously small nesting wave vectors.Furthermore,a peculiar quasiparticle decay process associated with the hω_(2) mode with a timescale of~1-2 ps is found below the transition temperature T*(~135 K).Our findings provide pivotal information for studying the fluctuating order parameters and their associated quasiparticle dynamics in various low-dimensional topological systems and other materials.
基金Project supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2019A1515011227)the National Natural Science Foundation of China(Grant No.51902353)+1 种基金the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.22lgqb03)the Fund from the State Key Laboratory of Optoelectronic Materials and Technologies(Grant No.OEMT-2022-ZRC-01)
文摘Polyyne,an sp~1-hybridized linear allotrope of carbon,has a tunable quasiparticle energy gap,which depends on the terminated chemical ending groups as well as the chain length.Previously,nitrogen doping was utilized to tailor the properties of different kinds of allotrope of carbon.However,how the nitrogen doping tailors the properties of the polyyne remains unexplored.Here,we applied the GW method to study the quasiparticle energy gaps of the N-doped polyynes with different lengths.When a C atom is substituted by an N atom in a polyyne,the quasiparticle energy gap varies with the substituted position in the polyyne.The modification is particularly pronounced when the second-nearest-neighboring carbon atom of a hydrogen atom is substituted.In addition,the nitrogen doping makes the Fermi level closer to the lowest unoccupied molecular orbital,resulting in an n-type semiconductor.Our results suggest another route to tailor the electronic properties of polyyne in addition to the length of polyyne and the terminated chemical ending groups.
基金supported by the National Natural Science Foundation of China(Grants Nos.10735010,10975072,11035001,11120101005 and 11165006)the National Major State Basic Research and Development of China(Grants Nos.2013CB834400 and 2010CB327803)+2 种基金CAS Knowledge Innovation Project(Grant No.KJCX2-SW-N02)the Research Fund of Doctoral Point(RFDP)(Grants No.20100091110028)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘We investigate the half-lives of β + /EC(electron capture) decay using the proton-neutron quasiparticle random-phase approximation(pnQRPA) with a δ-form Gamow-Teller residual interaction.Both particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix equation.The sensitivity of the calculated half-lives to some physical quantities used in the calculations is examined.Calculations are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = 76.Good agreement between experiment and theory is achieved especially for the nuclei far from stability,and the results of our calculations are discussed with comparison with other theoretical results.Predictions on the β-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11974257)the Distinguished Young Talent Funding of Jiangsu Province, China (Grant No. BK20200003)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Defect levels in semiconductor band gaps play a crucial role in functionalized semiconductors for practical applications in optoelectronics;however,first-principle defect calculations based on exchange-correlation functionals,such as local density approximation,grand gradient approximation(GGA),and hybrid functionals,either underestimate band gaps or misplace defect levels.In this study,we revisited iodine defects in CH_(3)NH_(3)PbI_(3) by combining the accuracy of total energy calculations of GGA and single-electron level calculation of the GW method.The combined approach predicted neutral Im_(i) to be unstable and the transition level of Im_(i)(+1/-1)to be close to the valence band maximum.Therefore,Im_(i) may not be as detrimental as previously reported.Moreover,Vm I may be unstable in the-1 charged state but could still be detrimental owing to the deep transition level of Vm I(+1/0).These results could facilitate the further understanding of the intrinsic point defect and defect passivation observed in CH_(3)NH_(3)PbI_(3).
基金Project supported by the National Natural Science Foundation of China(Grant No.11874337).
文摘We study the behaviors of three-dimensional double and triple Weyl fermions in the presence of weak random potential.By performing the Wilsonian renormalization group(RG)analysis,we reveal that the quasiparticle experiences strong renormalization which leads to the modification of the density of states and quasiparticle residue.We further utilize the RG analysis to calculate the classical conductivity and show that the diffusive transport is substantially corrected due to the novel behavior of the quasiparticle and can be directly measured by experiments.
