A New Type of Fermi-Liquid Fixed Point in Kondo Effect Due to (5f)2Configuration

Koga, Mikito; Shibata, Hiroyuki

doi:10.1143/jpsj.65.3007

Cited by 32 publications

(23 citation statements)

References 20 publications

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“…(ii) if we consider more complicated CEF model, the internal degrees of freedom at the impurity site cannot be described as the simple spin, e.g. in the case of CEF singlet for f 2 configuration, the irrelevant operator may have the tensor form in general 4) . The results suggest that the Kondo resonance states are individually formed in each channels and the interactions between them are irrelevant.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

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Competition between Hund-Rule Coupling and Kondo Effect

Kusunose¹,

Miyake

1997

J. Phys. Soc. Jpn.

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We investigate a problem about the competition between the hybridization and the Hundrule coupling by applying the Wilson numerical renormalization-group method to the extended Kondo model where the impurity spin interacts via the Hund-rule coupling, with an extra spin which is isolated from the conduction electrons. It is shown that the Hund-rule coupling is an irrelevant perturbation against the strong coupling fixed point. However, the Hund-rule coupling decreases the characteristic energy TK drastically to the lower side and the irrelevant operator, which describes the low energy physics, takes a form of ferromagnetic exchange interaction between the extra spin and the Kondo resonance states because of the existence of the Hundrule coupling.KEYWORDS: Hund-rule coupling, Kondo effect, numerical renormalization-group, anisotropic hybridization, plural electrons at localized orbitals, transition between high-spin and low-spin state, Uranium based heavy fermion, Ni-doped High-Tc cuprate §1. IntroductionOne of the most important question concerning heavy fermion systems 1) , which exhibit the exotic phenomena such as anisotropic superconductivity and extremely weak anitiferromagnetism is to understand how the low energy quasipartile states are formed, in other words, how the high energy incoherent states are reflected in the low energy physics. Many theoretical attempts have been made to include higher Crystalline Electric Field (CEF) effects both in single impurity 2,3,4,5) and lattice case 6,7,8) . When the degenerate orbitals are deformed by CEF, the hybridizations between the deformed orbitals and conduction electrons become anisotropic in general. The anisotropic hybridization produces different characteristic energies for each CEF orbitals. As a result, the orbital which concerns the Kondo effect changes depending on the temperature range.For Ce based compounds this anisotropy is reflected in the formation of highly renormalized quasiparticle band only through the one-body effect: its typical example has been put forward in Ref. 9 to explain anomalous properties observed in CeNiSn. On the other hand, for U based compounds, where (5f ) 2 or (5f ) 3 configuration is realized, the anisotropic hybridizations may be reflected on the quasiparticles through a many-body effect, because at least two characteristic energy scales and the Hund-rule coupling are involved in the problem. The "spin of localized electron" tends to be quenched by the Kondo effect, while the Hund-rule coupling stabilizes the high-spin state. Then a competition between the two effects plays a crucial role in determining the low energy physics.Such a competition is likely to be realized in a variety of physical situations: For example, (i) the magnetic susceptibility in UPd 2 Al 3 can be fitted by a certain CEF scheme under the tetravalent U state ((5f ) 2 configuration) 10) while the Fermi surface measured by dHvA effect is in good agreement with the band structure calculation with the trivalent state ((5f ) 3 configuration) 11) , and the pho...

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Section: Conclusion and Discussionmentioning

confidence: 99%

“…Many theoretical attempts have been made to include higher Crystalline Electric Field (CEF) effects both in single impurity 2,3,4,5) and lattice case 6,7,8) . When the degenerate orbitals are deformed by CEF, the hybridizations between the deformed orbitals and conduction electrons become anisotropic in general.…”

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confidence: 99%

Competition between Hund-Rule Coupling and Kondo Effect

Kusunose¹,

Miyake

1997

J. Phys. Soc. Jpn.

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“…There are also many theoretical discussions in f 2 impurity systems with the CEF singlet. [9][10][11][12][13] In considering possible ordering in non-Kramers lattice, we can draw analogy from the two-impurity Kondo problem and the f 2 impurity problem.…”

Section: Introductionmentioning

confidence: 99%

Electronic Orders Induced by Kondo Effect in Non-Kramersf-Electron Systems

2011

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This paper clarifies the microscopic nature of the staggered scalar order, which is specific to even number of f electrons per site. In such systems, crystalline electric field (CEF) can make a singlet ground state. As exchange interaction with conduction electrons increases, the CEF singlet at each site gives way to Kondo singlets. The collective Kondo singlets are identified with itinerant states that form energy bands. Near the boundary of itinerant and localized states, a new type of electronic order appears with staggered Kondo and CEF singlets. We present a phenomenological three-state model that qualitatively reproduces the characteristic phase diagram, which have been obtained numerically with use of the continuous-time quantum Monte Carlo combined with the dynamical mean-field theory. The scalar order observed in PrFe 4 P 12 is ascribed to this staggered order accompanying charge density wave (CDW) of conduction electrons. Accurate photoemission and tunneling spectroscopy should be able to probe sharp peaks both below and above the Fermi level in the ordered phase.

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“…Theoretical methods for studying the ST Kondo model include the poor man's scaling 3) and the numerical renormalization group (NRG). [4][5][6] For Pr skutterudites, the non-crossing approximation (NCA) and the NRG has recently been used for deriving the dynamics of the system. 7,8) In order to clarify the details of competition not only for the ground state but also for finite temperatures, however, more accurate theory is desirable.…”

Section: Introductionmentioning

confidence: 99%

Continuous-Time Quantum Monte Carlo Approach to Singlet–Triplet Kondo Systems

2009

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Dynamical properties are studied numerically for a variant of the Kondo model with singlet and triplet crystalline electric field (CEF) levels where Kondo and CEF singlets compete for the ground state. Using the continuous-time quantum Monte Carlo method, we derive the t-matrix of conduction electrons and dynamical susceptibilities of local electrons without encountering the negative sign problem. When the CEF splitting is comparable to the Kondo temperature, the dynamical response has only a quasi-elastic peak. Nevertheless, the local single-particle spectrum shows an energy gap in strong contrast with the ordinary Kondo model.

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A New Type of Fermi-Liquid Fixed Point in Kondo Effect Due to (5f)²Configuration

Cited by 32 publications

References 20 publications

Competition between Hund-Rule Coupling and Kondo Effect

Competition between Hund-Rule Coupling and Kondo Effect

Electronic Orders Induced by Kondo Effect in Non-Kramersf-Electron Systems

Continuous-Time Quantum Monte Carlo Approach to Singlet–Triplet Kondo Systems

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