Kondo lattice model studied with the finite temperature Lanczos method

Zerec, Ivica; Schmidt, B.; Thalmeier, Peter

doi:10.1103/physrevb.73.245108

Cited by 28 publications

(41 citation statements)

References 17 publications

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“…A description in terms of a cluster Doniach diagram is possible [22]: A transition criterion was established by comparing spin correlators. Recently, similar results have been presented for the 2D Kondo lattice model [23].…”

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Two-particle spin entanglement in magnetic Anderson nanoclusters

Samuelsson

Verdozzi

2007

Phys. Rev. B

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We investigate the two-particle spin entanglement in magnetic nanoclusters described by the periodic Anderson model. An entanglement phase diagram is obtained, providing a novel perspective on a central property of magnetic nanoclusters, namely the temperature dependent competition between local Kondo screening and nonlocal Ruderman-Kittel-Kasuya-Yoshida spin ordering. We find that multiparticle entangled states are present for finite magnetic field as well as in the mixed valence regime and away from half filling. Our results emphasize the role of charge fluctuations.PACS numbers: 3.67. Mn, 71.10.Fd, 75.75.+a In the last decade, solid state systems have emerged as a promising stage for quantum information processing, due to the prospect of scalability and integrability with conventional electronics. A successful realization of solid state quantum information processing requires a detailed control of the quantum mechanical properties of the system. In this respect, a key property is entanglement, or quantum mechanical correlations, between the individual quantum bits; entanglement plays the role of basic resource for a large number of quantum information schemes [1]. In nanoscale solid state systems, internal degrees of freedom of individual electrons, like spin or orbital states, are natural candidates for quantum bits. This offers considerable scope for studies of electronic entanglement in nanosystems.For spin entanglement, of particular interest are nanoclusters with magnetic impurities, realized experimentally e.g. by magnetic atoms on a surface [2], on a nanotube [3] or by coupled quantum dots [4]. Such nanoclusters display intriguing spin properties as the Kondo effect and antiferromagnetism, similar to what occurs in extended systems with dense magnetic impurities. For extended systems a central feature, described by the Doniach phase diagram [5], is the competition between formation of local Kondo spin singlets and a nonlocal Ruderman-Kittel-Kasuya-Yoshida (RKKY) spin ordering. A model which captures such behavior is the periodic Anderson model, PAM, a lattice of localized levels (with strong local repulsion) which hybridize with a conduction band. The PAM has been investigated intensively during the last decades [6] in connection with heavy fermion physics, non-fermi liquid behavior, etc [7].To date, no studies are however available for entanglement in the PAM, only the related single [8] and two [9] impurity Anderson models and the simplified Kondo necklace model [10] have been considered. There are also investigations of entanglement in various spin cluster models [11,12]. None of these models do however correctly capture the interplay of spin correlations and charge dynamics, characteristic of the PAM [6]. Only very recently the interest turned to systems where charge dynamics is important [13,14]. These investigations however only concerned the Hubbard model, focusing on entanglement in extended systems, at quantum phase transitions [15]. An investigation of the entanglement in nanoclusters desc...

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Two-particle spin entanglement in magnetic Anderson nanoclusters

Samuelsson

Verdozzi

2007

Phys. Rev. B

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“…Inserting the above expressions into the Hamiltonian of Eqs. (10,11) one obtains a bilinear form in the triplet fluctuation operators (û k ,d k ,t kz ) which may be diagonalised with two separate Bogoliubov transformations given for the z-polarisation by…”

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confidence: 99%

Field-induced quantum phase transition in the anisotropic Kondo necklace model

Thalmeier

Langari

2007

Phys. Rev. B

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The anisotropic Kondo necklace model in 2D and 3D is treated as a genuine model for magnetic to Kondo singlet quantum phase transitions in the heavy fermion (HF) compounds. The variation of the quantum critical point (QCP) with anisotropy parameters has been investigated previously in the zero field case [1]. Here we extend the treatment to finite fields using a generalised bond operator representation including all triplet states. The variation of critical tc with magnetic field and the associated phase diagram is derived. The influence of anisotropies and the different gfactors for localised and itinerant spins on the field dependence of tc is also investigated. It is found that three different types of behaviour may appear: (i) Destruction of antiferromangetism and appearance of a singlet state above a critical field. (ii) The inverse behaviour, namely field induced antiferromagnetism out of the Kondo singlet phase. (iii) Reentrance behaviour of the Kondo singlet phase as function of field strength.

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“…In addition the Kondo term in the KLM induces an indirect RKKY exchange interaction between local spins on different sites [3]. In a real material RKKY interactions may lead to a magnetically ordered ground state.…”

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confidence: 99%