Ground-State Dynamical Correlation Functions: An Approach from Density Matrix Renormalization Group Method

A numerical approach to ground-state dynamical correlation functions from Density Matrix Renormalization Group (DMRG) is developed. Using sum rules, moments of a dynamic correlation function can be calculated with DMRG, and with the moments the dynamic correlation function can be obtained by the maximum entropy method. We apply this method to one-dimensional spinless fermion system, which can be converted to the spin 1/2 Heisenberg model in a special case. The dynamical density-density correlation function is obtained.Comment: 11 pages, latex, 4 figure

Phase Diagram of the Two-Channel Kondo Lattice

The phase diagram of the two-channel Kondo lattice model is examined with a Quantum Monte Carlo simulation in the limit of infinite dimensions. Commensurate (and incommensurate) antiferromagnetic and superconducting states are found. The antiferromagnetic transition is very weak and continuous; whereas the superconducting transition is discontinuous to an odd-frequency channel-singlet and spin-singlet pairing state.Comment: 5 pages, LaTeX and 4 PS figures (see also cond-mat/9609146 and cond-mat/9605109

Two-Channel Kondo Lattice: An Incoherent Metal

The two-channel Kondo lattice model is examined with a Quantum Monte Carlo simulation in the limit of infinite dimensions. We find non-fermi-liquid behavior at low temperatures including a finite low-temperature single-particle scattering rate, the lack of a fermi edge and Drude weight. However, the low-energy density of electronic states is finite. Thus, we identify this system as an incoherent metal. We discuss the relevance of our results for concentrated heavy fermion metals with non-Fermi-Liquid behavior.Comment: LaTex, 5 pages, 3 Postscript files. Revision - in reference 5 and 6(a

Two-Channel Kondo Lattice: An Incoherent Metal

The paramagnetic phase of the two-channel Kondo lattice model is examined with a quantum Monte Carlo simulation in the limit of infinite dimensions. We find non-Fermi-liquid behavior at low temperatures including a finite low-temperature single-particle scattering rate, no Fermi distribution discontinuity, and zero Drude weight. However, the low-energy density of electronic states is finite. We label our model system in this phase an "incoherent metal." We discuss the relevance of our results for concentrated heavy fermion metals with non-Fermi-liquid behavior. [S0031-9007(96) The Fermi liquid theory of Landau has provided a remarkably robust paradigm for describing the properties of interacting fermion systems such as liquid 3 He and alkali metals (e.g., sodium). The key notion of this theory is that the low lying excitations of the interacting system possess a 1:1 map to those of the noninteracting system and hence are called "quasiparticles." In the metallic context, one may think of the quasiparticles as propagating electronlike wave packets with renormalized magnetic moment and effective mass reflecting the "molecular field" of the surrounding medium. A sharp Fermi surface remains in the electron occupancy function n k which measures the number of electrons with a given momentum, and for energies v and temperatures T asymptotically close to the Fermi surface the excitations have a decay rate going as v 2 1 p 2 ͑k B T͒ 2 , which is much smaller than the quasiparticle energy, and generally translates into a T 2 contribution to the electrical resistivity r͑T ͒. This theory has proven useful in describing phase transitions within the Fermi liquid, such as superconductivity which is viewed as a pairing of Landau quasiparticles in conventional metals such as aluminum. The Fermi liquid paradigm appears now to be breaking down empirically in numerous materials, notably the quasi-two-dimensional cuprate superconductors [1] and a number of fully three-dimensional heavy Fermion alloys and compounds Among the remaining theories to explain experiment are those based upon proximity to a zero-temperature quantum critical point In this Letter, we present the first rigorous solution of the two-channel Kondo lattice model in infinite spatial dimensions. We find that the paramagnetic phase of this model is an "incoherent metal" with finite density of states at the Fermi energy and finite residual resistivity. The excitation spectrum is non-Fermi-liquidlike; in particular, there is a finite lifetime for electrons at the Fermi energy, an ill defined quasiparticle mass, a linear low-temperature electrical resistivity with a finite residual value, and no discontinuity in n k . We find that physical quantities may be suitably scaled with a lattice Kondo scale T 0 that is significantly enhanced over the impurity limit. We discuss the possible relevance of these results to understand transport properties of concentrated heavy electron materials. The two-channel Kondo impurity model consists of two identical species of noninteracting electrons antiferromagnetically coupled to a spin 1͞2 impurity. Non-Fermiliquid behavior results because of the inability to screen out the impurity spin: it is energetically favorable for both conduction electron bands to couple to the impurity which gives a spin 1͞2 complex on all length scales. As a result, the ground state is degenerate and the excitation spectrum non-Fermi-liquidlike. In contrast, the single-channel Kondo model has a singlet ground state with the impurity spin screened out, and a Fermi liquid excitation spectrum corresponding to the removal of one conduction state from the system. On extension to the lattice and ignoring the renormalization of the environment around each spin, the array of single-channel model singlets would simply renormalize the potential scattering. In contrast, the 1612 0031-9007͞ 96͞77(8)͞1612(4)$10.0