Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To t...Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To this end,we employ the algebraic equation of motion approach to calculate the TIAM and analytically obtain the explicit singleparticle impurity Green function under the soft cut-off approximation(SCA). This approach effectively incorporates the impurity spacing as an intrinsic parameter. By solving the pole equations of the Green function, we have, for the first time, qualitatively calculated the spectral weight functions of the corresponding low-energy excitations. We find that when the impurity spacing is less than one lattice distance, the dynamic Rudermann–Kittel–Kasuya–Yosida(RKKY) interaction effectively enters, resulting in a rapid increase in the spectral weights of the RKKY phase, which ultimately surpass those of the Kondo phase;while the spectral weights of the Kondo phase are strongly suppressed. From the perspective of spectral weights, we further confirm the existence of a crossover from the Kondo phase to the RKKY phase in the TIAM. Based on these results, the reasons for the phenomenon of the Kondo resonance splitting are also discussed.展开更多
Using the dynamical Monte Carlo method we investigate the nonequilibrium effects in RKKY-coupling disordered spin glass. By the simulation we reproduce the well-known aging and memory phenomena and find the energy rel...Using the dynamical Monte Carlo method we investigate the nonequilibrium effects in RKKY-coupling disordered spin glass. By the simulation we reproduce the well-known aging and memory phenomena and find the energy relaxation at a certain temperature happens only to the corresponding spins, which directly causes the nonequilibrium effects. Combining the master equation and the energy relaxation we analyse these phenomena and explain them from the dynamical perspective.展开更多
Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by ...Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order-disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy △xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy AxL decreases （increases） on increasing the non-magnetic spacer of thickness M （on increasing the crystal field）, and AxL undergoes oscillations as a function of the Fermi level.展开更多
We present a theory of both the itinerant carrier-mediated RKKY interaction and the virtual excitations-mediated Bloembergen–Rowland(BR)interaction between magnetic moments in graphene induced by proximity effect wit...We present a theory of both the itinerant carrier-mediated RKKY interaction and the virtual excitations-mediated Bloembergen–Rowland(BR)interaction between magnetic moments in graphene induced by proximity effect with a ferromagnetic film.It is shown that the RKKY/BR interaction consists of the Heisenberg,Ising,and Dzyaloshinskii–Moriya(DM)terms.In the case of the nearest distance,we estimate the DM term from the RKKY/BR interaction is about$0.13$meV for the graphene/Co interface,which is consistent with the experimental result of DM interaction$0.16\pm0.05$meV.Our calculations indicate that the intralayer RKKY/BR interaction may be a possible physical origin of the DM interaction in the graphene-ferromagnet interface.This work provides a new perspective to comprehend the DM interaction in graphene/ferromagnet systems.展开更多
In this letter,a theoretical fit of nuclear magnetic resonance spectra of ^(63)Cu in Cu layers of Fe/Cu multilayers is given based on RKKY theory.The values of exchange field and additional Knight shift are fitted,whi...In this letter,a theoretical fit of nuclear magnetic resonance spectra of ^(63)Cu in Cu layers of Fe/Cu multilayers is given based on RKKY theory.The values of exchange field and additional Knight shift are fitted,which agree approximately with the experimental data.展开更多
In our previous work [1] we calculated RKKY interaction between two magnetic impurities in pristine graphene using the Green’s functions (GF) in the coordinate-imaginary time representation. Now we show that the calc...In our previous work [1] we calculated RKKY interaction between two magnetic impurities in pristine graphene using the Green’s functions (GF) in the coordinate-imaginary time representation. Now we show that the calculations of the GF in this representation can be simplified by using the Feynman’s trick, which allows to easily calculate RKKY interaction in gapped graphene. We also present calculations of the RKKY interaction in gapped or doped graphene using the coordinate-imaginary frequency representation. Both representations, corresponding to calculation of the bubble diagram in Euclidean space, have an important advantage over those corresponding to calculation in Minkowskii space, which are very briefly reviewed in the Appendix to the present work. The former, in distinction to the latter, operate only with the convergent integrals from the start to the end of the calculation.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 11974420)。
文摘Understanding the quantum critical phenomena is one of the most important and challenging tasks in condensed matter physics and the two-impurity Anderson model(TIAM) is a good starting point for this exploration. To this end,we employ the algebraic equation of motion approach to calculate the TIAM and analytically obtain the explicit singleparticle impurity Green function under the soft cut-off approximation(SCA). This approach effectively incorporates the impurity spacing as an intrinsic parameter. By solving the pole equations of the Green function, we have, for the first time, qualitatively calculated the spectral weight functions of the corresponding low-energy excitations. We find that when the impurity spacing is less than one lattice distance, the dynamic Rudermann–Kittel–Kasuya–Yosida(RKKY) interaction effectively enters, resulting in a rapid increase in the spectral weights of the RKKY phase, which ultimately surpass those of the Kondo phase;while the spectral weights of the Kondo phase are strongly suppressed. From the perspective of spectral weights, we further confirm the existence of a crossover from the Kondo phase to the RKKY phase in the TIAM. Based on these results, the reasons for the phenomenon of the Kondo resonance splitting are also discussed.
文摘Using the dynamical Monte Carlo method we investigate the nonequilibrium effects in RKKY-coupling disordered spin glass. By the simulation we reproduce the well-known aging and memory phenomena and find the energy relaxation at a certain temperature happens only to the corresponding spins, which directly causes the nonequilibrium effects. Combining the master equation and the energy relaxation we analyse these phenomena and explain them from the dynamical perspective.
文摘Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order-disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy △xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy AxL decreases （increases） on increasing the non-magnetic spacer of thickness M （on increasing the crystal field）, and AxL undergoes oscillations as a function of the Fermi level.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11404043 and 1160041160)the Key Technology Innovations Project to Industries of Chongqing(Grant No.cstc2016zdcy-ztzx0067)the Graduate Research Innovation Project of Chongqing(Grants No.CYS18253).
文摘We present a theory of both the itinerant carrier-mediated RKKY interaction and the virtual excitations-mediated Bloembergen–Rowland(BR)interaction between magnetic moments in graphene induced by proximity effect with a ferromagnetic film.It is shown that the RKKY/BR interaction consists of the Heisenberg,Ising,and Dzyaloshinskii–Moriya(DM)terms.In the case of the nearest distance,we estimate the DM term from the RKKY/BR interaction is about$0.13$meV for the graphene/Co interface,which is consistent with the experimental result of DM interaction$0.16\pm0.05$meV.Our calculations indicate that the intralayer RKKY/BR interaction may be a possible physical origin of the DM interaction in the graphene-ferromagnet interface.This work provides a new perspective to comprehend the DM interaction in graphene/ferromagnet systems.
基金Supported by National Natural Science Foundation of ChinaState Education Commission and State Key Laboratory of Magnetism.
文摘In this letter,a theoretical fit of nuclear magnetic resonance spectra of ^(63)Cu in Cu layers of Fe/Cu multilayers is given based on RKKY theory.The values of exchange field and additional Knight shift are fitted,which agree approximately with the experimental data.
文摘In our previous work [1] we calculated RKKY interaction between two magnetic impurities in pristine graphene using the Green’s functions (GF) in the coordinate-imaginary time representation. Now we show that the calculations of the GF in this representation can be simplified by using the Feynman’s trick, which allows to easily calculate RKKY interaction in gapped graphene. We also present calculations of the RKKY interaction in gapped or doped graphene using the coordinate-imaginary frequency representation. Both representations, corresponding to calculation of the bubble diagram in Euclidean space, have an important advantage over those corresponding to calculation in Minkowskii space, which are very briefly reviewed in the Appendix to the present work. The former, in distinction to the latter, operate only with the convergent integrals from the start to the end of the calculation.
