In this paper the electronic structure of A1B2-type USi2 has been explored using DFT, DFT＋U and hybrid functional （HSE） methods. It reveals that c/a has great effect on the electronic structure, particularly thefor...In this paper the electronic structure of A1B2-type USi2 has been explored using DFT, DFT＋U and hybrid functional （HSE） methods. It reveals that c/a has great effect on the electronic structure, particularly theforbitals, and there exists strong hybridization between the Si-p and U-d orbitals in A1B2-type USi2. These calculations uncover that there exists similarities on the crystal structure and the electronic structure between AIB2-type USi2 and UaSis. Present calculations provide a further insight on the U3Si5, a heavy-fermion system.展开更多
In a two component fermion system, the mismatched Fermi surfaces prevent the formation of Cooper pairsbetween the two spices near their average Fermi surface. Our previous work[1] has shown that the angle dependenceof...In a two component fermion system, the mismatched Fermi surfaces prevent the formation of Cooper pairsbetween the two spices near their average Fermi surface. Our previous work[1] has shown that the angle dependenceof the non s-wave pairing gap can reduce the effect of the difference μ between the Fermi surfaces of two spices inasymmetric nuclear matter. On the other hand, in the heavy fermion superconductors, such as CeCoIn5 pressuredCeRhIn5 NpPd5Al2 and Tl-based cuprates, may have a couple of common features, for example, the d-wave pairingand a strong paramagnetic effect (the difference of the two Fermi surfaces μ). Therefore, the angle dependence ofthe pairing gap may have significant influence in these systems.展开更多
We discuss the process of equilibrium’s attainment in an interacting many-fermions system linked to a heat reservoir, whose temperature <em>T</em> is subject to a short-time disturbance of total duration ...We discuss the process of equilibrium’s attainment in an interacting many-fermions system linked to a heat reservoir, whose temperature <em>T</em> is subject to a short-time disturbance of total duration 2<span style="white-space:nowrap;"><em>τ</em>.</span> In this time-interval, its temperature increases up to a maximum value , cooling off afterward (also gradually) to its original value T<sub><em>M</em></sub>. The process is described by a typical master equation that leads eventually to equilibration. We discuss how the equilibration process depends upon 1) the system’s fermion-number, 2) the fermion-fermion interaction’s strength <em>V</em>, 3) the disturbance duration <span style="white-space:nowrap;"><span style="white-space:nowrap;">2<span style="white-space:nowrap;"><em>τ</em></span></span></span><em></em>, and finally 4) the maximum number of equations <em>N</em> of the master equation.展开更多
The two-componenl exciton model is applied for calculating the data ofnucleon induced reactions.The angular momentum and parity conservations are takeninto account.In terms of the calculated results of n+<sup>56...The two-componenl exciton model is applied for calculating the data ofnucleon induced reactions.The angular momentum and parity conservations are takeninto account.In terms of the calculated results of n+<sup>56</sup>Fe at E<sub>n</sub>=14.5 MeV the physicalpicture of the two-component model has been analysed.展开更多
Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 （2015）] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002...Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 （2015）] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 （2015）] of the Yb-doped heavy fermion superconductor CeCoIns, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfiuid density response function in the celebrated Kondo- Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large-N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfiuid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1-xYbxCoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.展开更多
Motivated by the growing interest in the novel quantum phases in materials with strong electron correlations and spin–orbit coupling, we study the interplay among the spin–orbit coupling, Kondo interaction, and magn...Motivated by the growing interest in the novel quantum phases in materials with strong electron correlations and spin–orbit coupling, we study the interplay among the spin–orbit coupling, Kondo interaction, and magnetic frustration of a Kondo lattice model on a two-dimensional honeycomb lattice.We calculate the renormalized electronic structure and correlation functions at the saddle point based on a fermionic representation of the spin operators.We find a global phase diagram of the model at half-filling, which contains a variety of phases due to the competing interactions.In addition to a Kondo insulator, there is a topological insulator with valence bond solid correlations in the spin sector, and two antiferromagnetic phases.Due to the competition between the spin–orbit coupling and Kondo interaction, the direction of the magnetic moments in the antiferromagnetic phases can be either within or perpendicular to the lattice plane.The latter antiferromagnetic state is topologically nontrivial for moderate and strong spin–orbit couplings.展开更多
文摘In this paper the electronic structure of A1B2-type USi2 has been explored using DFT, DFT＋U and hybrid functional （HSE） methods. It reveals that c/a has great effect on the electronic structure, particularly theforbitals, and there exists strong hybridization between the Si-p and U-d orbitals in A1B2-type USi2. These calculations uncover that there exists similarities on the crystal structure and the electronic structure between AIB2-type USi2 and UaSis. Present calculations provide a further insight on the U3Si5, a heavy-fermion system.
文摘In a two component fermion system, the mismatched Fermi surfaces prevent the formation of Cooper pairsbetween the two spices near their average Fermi surface. Our previous work[1] has shown that the angle dependenceof the non s-wave pairing gap can reduce the effect of the difference μ between the Fermi surfaces of two spices inasymmetric nuclear matter. On the other hand, in the heavy fermion superconductors, such as CeCoIn5 pressuredCeRhIn5 NpPd5Al2 and Tl-based cuprates, may have a couple of common features, for example, the d-wave pairingand a strong paramagnetic effect (the difference of the two Fermi surfaces μ). Therefore, the angle dependence ofthe pairing gap may have significant influence in these systems.
文摘We discuss the process of equilibrium’s attainment in an interacting many-fermions system linked to a heat reservoir, whose temperature <em>T</em> is subject to a short-time disturbance of total duration 2<span style="white-space:nowrap;"><em>τ</em>.</span> In this time-interval, its temperature increases up to a maximum value , cooling off afterward (also gradually) to its original value T<sub><em>M</em></sub>. The process is described by a typical master equation that leads eventually to equilibration. We discuss how the equilibration process depends upon 1) the system’s fermion-number, 2) the fermion-fermion interaction’s strength <em>V</em>, 3) the disturbance duration <span style="white-space:nowrap;"><span style="white-space:nowrap;">2<span style="white-space:nowrap;"><em>τ</em></span></span></span><em></em>, and finally 4) the maximum number of equations <em>N</em> of the master equation.
文摘The two-componenl exciton model is applied for calculating the data ofnucleon induced reactions.The angular momentum and parity conservations are takeninto account.In terms of the calculated results of n+<sup>56</sup>Fe at E<sub>n</sub>=14.5 MeV the physicalpicture of the two-component model has been analysed.
文摘Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 （2015）] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 （2015）] of the Yb-doped heavy fermion superconductor CeCoIns, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfiuid density response function in the celebrated Kondo- Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large-N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfiuid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1-xYbxCoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.
基金Project supported by the Ministry of Science and Technology of China,the National Key R&D Program of China(Grant No.2016YFA0300504)the National Natural Science Foundation of China(Grant No.11674392)+3 种基金the Research Funds of Remnin University of China(Grant No.18XNLG24)part supported by the NSF Grant DMR-1920740the Robert A.Welch Foundation Grant C-1411support by a Ulam Scholarship from the Center for Nonlinear Studies at Los Alamos National Laboratory
文摘Motivated by the growing interest in the novel quantum phases in materials with strong electron correlations and spin–orbit coupling, we study the interplay among the spin–orbit coupling, Kondo interaction, and magnetic frustration of a Kondo lattice model on a two-dimensional honeycomb lattice.We calculate the renormalized electronic structure and correlation functions at the saddle point based on a fermionic representation of the spin operators.We find a global phase diagram of the model at half-filling, which contains a variety of phases due to the competing interactions.In addition to a Kondo insulator, there is a topological insulator with valence bond solid correlations in the spin sector, and two antiferromagnetic phases.Due to the competition between the spin–orbit coupling and Kondo interaction, the direction of the magnetic moments in the antiferromagnetic phases can be either within or perpendicular to the lattice plane.The latter antiferromagnetic state is topologically nontrivial for moderate and strong spin–orbit couplings.
