Random Kondo alloys investigated with the coherent potential approximation

Burdin, Sébastien; Fulde, Peter

doi:10.1103/physrevb.76.104425

Cited by 31 publications

(57 citation statements)

References 43 publications

(56 reference statements)

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“…Further, the dominant influence of the conduction-band filling furnishes a link between the problem studied here and a seemingly different one, namely a Kondo lattice with random depletion of local moments. [25][26][27] We note that partial Kondo screening, somewhat similar to the regime advertised in Fig. 1, has been predicted to occur in certain frustrated Kondo lattices, where a spontaneous modulation of the Kondo effect is instrumental in releasing geometric frustration.…”

Section: A General Considerationssupporting

confidence: 56%

Kondo lattices with inequivalent local moments: Competitive versus cooperative Kondo screening

2011

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While standard heavy fermion metals feature a single spin-1/2 local moment per unit cell, more complicated systems with multiple distinct local moments have been synthesized as well, with Ce3Pd20(Si,Ge)6 being one example. Here, we discuss the physics of a Kondo lattice model with two local-moment sublattices, coupled with different Kondo couplings to conduction electrons. The phase diagram will be strongly modified from that of the standard Kondo lattice if the characteristic screening temperatures of the distinct moments are well separated. Therefore, we investigate the interplay between the two Kondo effects using a local self-energy approximation via slave bosons. We find that the two Kondo effects can either compete or co-operate depending on the conductionband filling. In the regime of competition, small differences in the two Kondo couplings can lead to huge differences in the respective Kondo scales, due to non-trivial many-body effects. We also study the low-temperature properties of the collective heavy Fermi-liquid state and propose a connection to depleted Kondo lattice systems.

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Section: A General Considerationssupporting

confidence: 56%

Kondo lattices with inequivalent local moments: Competitive versus cooperative Kondo screening

2011

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“…In that case, T 0 and T K approach each other and the 'slow' crossover does not occur. For x > 0.5, one can expect a crossover from a lattice regime with T 0 =T K to a universal dilute regime with T K =T 0 , as discussed in Ref 35 . The slave boson dispersion defined by the Hamiltonian in Eq.…”

Section: The T0 ≪ Tk Casementioning

confidence: 88%

Multiple temperature scales of the periodic Anderson model: Slave boson approach

Burdin

Zlatič

2009

Phys. Rev. B

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The thermodynamic and transport properties of intermetallic compounds with Ce, Eu, and Yb ions are discussed using the periodic Anderson model with an infinite correlation between f electrons. At high temperatures, these systems exhibit typical features that can be understood in terms of a single impurity Anderson or Kondo model with Kondo scale TK . At low temperatures, the normal state is governed by the Fermi liquid (FL) laws with characteristic energy scale T0. The slave boson solution of the periodic model shows that T0 and TK depend not only on the degeneracy and the splitting of the f states, the number of c and f electrons, and their coupling, but also on the shape of the conduction electrons density of states (c DOS) in the vicinity of the chemical potential.We show that the details of the band structure determine the ratio T0/TK and that the crossover between the high-and low-temperature regimes in ordered compounds is system-dependent. A sharp peak in the c DOS yields T0 ≪TK and explains the 'slow crossover' observed in YbAl3 or YbMgCu4. A minimum in the c DOS yields T0 ≫TK , which leads to the abrupt transition between the high-and low-temperature regimes in YbInCu4. In the case of CeCu2Ge2 and CeCu2Si2, where T0 ≃ TK , the slave boson solution explains the pressure experiments which reveal sharp peaks in the T 2 coefficient of the electrical resistance, A = ρ(T )/T 2 , and the residual resistance. These peaks are due to the change in the degeneracy of the f states induced by the applied pressure.The FL laws explain also the correlation between the specific heat coefficient γ = CV /T and the slope of the thermopower α(T )/T , or between γ and the A coefficient of the resistivity. For N -fold degenerate model, the FL laws explain the deviations from universal value of the Kadowaki-Woods ratio, RKW = A/γ 2 , and the ratio q = lim {T →0} α/γT . The renormalization of transport coefficients can invalidate the Wiedemann-Franz law and lead to an enhancement of the thermoelectric figure-ofmerit. We show that the low-temperature response of the periodic Anderson model can be enhanced (or reduced) with respect to the predictions based on the single-impurity models that give the same high-temperature behavior.

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“…The electronic exhaustion problem [13,14] suggested by Nozières remained a long standing issue for years [15][16][17][18][19][20][21][22][23] and was finally understood [21,24]: the Kondo temperature T K that characterizes the crossover to the low temperature Kondo screening regime, and the Fermi liquid energy scale T coh that characterizes the CFL are indeed the same energy scale. It was shown that the ratio T K /T coh still depends on the electronic filling and lattice structure [21,25,26]. But this ratio was proven not to depend on the Kondo coupling as it was wrongly thought initially [21,22,24].A simple picture of the periodic dense Kondo lattice model had been provided within the strong Kondo coupling limit [14,15,[27][28][29].…”

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confidence: 99%

Lifshitz Transition in Kondo Alloys

Burdin

Lacroix²

2013

Phys. Rev. Lett.

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We study the low-energy states of Kondo alloys as a function of the magnetic impurity concentration per site x and the conduction electron average site occupation n(c). Using two complementary approaches, the mean-field coherent potential approximation and the strong-coupling limit, we identify and characterize two different Fermi-liquid regimes. We propose that both regimes are separated by a Lifshitz transition at x=n(c). Indeed, we predict a discontinuity of the number of quasiparticles that are enclosed in the Fermi surface. This feature could provide a scenario for the non-Fermi liquid properties that were recently observed in Kondo alloy systems around x=n(c).

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Random Kondo alloys investigated with the coherent potential approximation

Cited by 31 publications

References 43 publications

Kondo lattices with inequivalent local moments: Competitive versus cooperative Kondo screening

Kondo lattices with inequivalent local moments: Competitive versus cooperative Kondo screening

Multiple temperature scales of the periodic Anderson model: Slave boson approach

Lifshitz Transition in Kondo Alloys

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