On the solution of the Coqblin-Schreiffer Hamiltonian by the large-N expansion technique

Read, N.; Newns, D. M.

doi:10.1088/0022-3719/16/17/014

Cited by 591 publications

(434 citation statements)

References 14 publications

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“…Similarly, in this approach Q ia and Q ia are introduced as fluctuating bosonic Hubbard-Stratonovich fields that upon functional integration reproduces the appropriate fourfermion terms. [21][22][23] In this context, λ i and N i can also be interpreted as the temporal components of a U (1) and an SU (2) gauge field, respectively. Together, they corresponds to the U (2) ∼ U (1) × SU (2) gauge redundancy f iaα → U ab i f ibα of the spinons.…”

Section: A Slave-particle Representation and Its Mean-fieldmentioning

confidence: 99%

Ordering and criticality in an underscreened Kondo chain

Jiang

Rau

2013

Phys. Rev. B

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Motivated by the nickel valence controversy in the perovskite nickelate RNiO3, we consider a one-dimensional underscreened Kondo chain consisting of alternating spin-1 ("nickel") and electron ("oxygen") sites, which in addition to the usual electron hopping and spin-spin interaction between the S = 1 spin and the electron also contains a spin mediated electron hopping term. Using the density-matrix renormalization group (DMRG), we obtained the zero temperature phase diagram of the model, as well as various correlation functions in each phase. Importantly, for certain range of parameters the model exhibits a quasi-long-range spiral (QS) order. To understand the DMRG results, we construct a mean-field theory based on a Schwinger fermion decomposition of the S = 1 spins, from which we argue that the QS phase corresponds to a phase in proximity to the spin Bose metal state proposed by Sheng, Motrunich, and Fisher [Phys. Rev. B, 79, 205112 (2009)]. Notably, we find no evidence for a phase with the symmetry of "nickel"-centered charge order, which has been argued to arise due to site-selective Kondo screening of half the S = 1 spins, and suggest that order of this type occurs only due to an additional energy gain from spontaneous lattice distortions, not present in this model.

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Section: A Slave-particle Representation and Its Mean-fieldmentioning

confidence: 99%

Ordering and criticality in an underscreened Kondo chain

Jiang

Rau

2013

Phys. Rev. B

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“…Within the mean-field theory approximation controlled by the parameter 1/N where N is given by the degeneracy of the f -orbital multiplet, it follows: 18…”

Section: Discussionmentioning

confidence: 99%

“…From the analysis of the momentum integrals (3) it is clear that both u( r ij ) and v( r ij ) will decay as ∼ 1/r n ij since functions u k and v k are analytic functions of momentum.The values of µ, f and V l can be found by employing slave boson meanfield theory. 18 In order to compute the spacial dependence of the coherence factors, I have solved the mean-field equations 24 assuming that f -orbital multiplet is sixfold degenerate When the heavy-electron leaves the tip and the distance between the tip and surface is about several lattice spacings it is clear that the heavy-electron will retain its composite nature.…”

Section: Discussionmentioning

confidence: 99%

“…17 It is important to note, however, that the Fano lineshape of the tunneling conductance appears only for the case when the f -electron level acquires a finite lifetime. 13 Within the currently used meanfield theory approaches [18][19][20][21][22] finite lifetime of the f -level can either be introduced on the phenomenological level or derived by taking into account the fluctuation corrections to the meanfield theory. 22 In this paper, I will review these ideas by using the junction between the two heavy fermion metals as an example.…”

Section: Tunneling Into a Kondo Lattice: Overviewmentioning

confidence: 99%

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Tunneling in Heavy-Fermion Junctions

Dzero

2014

J. Phys. Soc. Jpn.

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In this paper I review recent theoretical and experimental advances in understanding of tunneling processes between normal metals and metals containing electrons which occupy partially filled f -orbitals. In heavy-fermion materials the effective mass of the quasiparticles far exceeds the bare electron mass due to strong hybridization between conduction and f -orbital states. Kondo lattices form a class of heavy-fermion systems in which an average occupation number of f -electron states is close to an integer. Therefore, the tunneling into a Kondo lattice necessarily involves co-tunneling process of a tip electron into an f -electron state of a Kondo lattice. This co-tunneling process is manifested in the Fano-lineshape of differential conductance as a function of an applied voltage, which has been routinely observed in recent experiments on various Kondo lattice systems. To illustrate these ideas, I discuss the problem of the tunneling junction when the single particle states in the tip are also a product of hybridization between conduction and f -states, i.e. tunneling between two heavy-fermion materials.

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“…Since the original paper by Kondo 1 considering electron sea screening a single impurity spin, this problem has attracted significant theoretical and experimental attention. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] More recently, impurity physics has been studied in the context of strongly interacting systems. Numerous examples include 21 an impurity in systems with vanishing density of states 22,23 high temperature superconductors, 24 and quantum magnets.…”

Section: Introductionmentioning

confidence: 99%

Overscreened Kondo fixed point inS=1spin liquid

2013

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We propose a possible realization of the overscreened Kondo impurity problem by a magnetic s = 1/2 impurity embedded in a two-dimensional S = 1 U (1) spin liquid with a Fermi surface. This problem contains an interesting interplay between non-Fermi-liquid behavior induced by a U (1) gauge field coupled to fermions and a non-Fermi-liquid fixed point in the overscreened Kondo problem. Using a large-N expansion together with an expansion in the dynamical exponent of the gauge field, we find that the coupling to the gauge field leads to weak but observable changes in the physical properties of the system at the overscreened Kondo fixed point. We discuss the extrapolation of this result to a physical case and argue that the realization of overscreened Kondo physics could lead to observations of effects due to gauge fields.

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On the solution of the Coqblin-Schreiffer Hamiltonian by the large-N expansion technique

Cited by 591 publications

References 14 publications

Ordering and criticality in an underscreened Kondo chain

Ordering and criticality in an underscreened Kondo chain

Tunneling in Heavy-Fermion Junctions

Overscreened Kondo fixed point inS=1spin liquid

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