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

Novel electronic order is found theoretically for a system where even number of localized electrons per site are coupled with conduction electrons. For precise quantitative study, a variant of the Kondo lattice model is taken with crystalline electric field (CEF) singlet and triplet states for each site. Using the dynamical mean-field theory combined with the continuous-time quantum Monte Carlo method, a staggered order with alternating Kondo and CEF singlets is identified for a case with one conduction electron per site being distributed in two conduction bands each of which is quarter-filled. This electronic order accompanies a charge density wave (CDW) of conduction electrons that accumulate more on Kondo-singlet sites than on CEFsinglet sites. Possible relevance of the present order to the scalar order in PrFe4P12 is discussed.

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“…In the DMFT, the vertices in eqs. (9) and (12) are the same. Hence, we can obtain χ λλ ′ by solving these equations simultaneously.…”

Section: Susceptibilities With Two-sublatticesmentioning

confidence: 99%

“…The parameter α γ is chosen as 0 for ferromagnetic interaction (J γ < 0) and 1 for antiferromagnetic coupling (J γ > 0) in order to avoid the minus sign problem as noted in ref. 9. The constant term may be neglected in the simulation.…”

Section: Ct-qmc Algorithmmentioning

confidence: 99%

Electronic Order with Staggered Kondo and Crystalline Electric Field Singlets

2010

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“…In interacting electron systems with two f -electrons per site as in some Pr and U compounds, the distinction between itinerant and localized characters of electrons is not as explicit as in Ce or Yb compounds with f 1 or f 13 configuration, respectively. The difference comes from the Kramers degeneracy; the ground state of each non-Kramers ion such as Pr 3+ or U 4+ can be a singlet even without Kondo effect provided the CEF favors the non-degenerate ground state.…”

Section: Introductionmentioning

confidence: 99%

“…The difference comes from the Kramers degeneracy; the ground state of each non-Kramers ion such as Pr 3+ or U 4+ can be a singlet even without Kondo effect provided the CEF favors the non-degenerate ground state. On the contrary, the Kramers degeneracy in f 1 or f 13 can only be removed by exchange (Kondo) interaction with conduction electrons. The dichotomy between itinerant and localized characters of f -electrons leads to intriguing phenomena in heavy fermion systems.…”

Section: Introductionmentioning

confidence: 99%

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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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Composite electronic orders induced by orbital Kondo effect

Kuramoto

2016

Science Bulletin

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In a large number of rare-earth and actinide systems, Kondo effect tends to suppress magnetic order by making the spin singlet between localized and conduction electron spins. In the presence of orbital degrees of freedom, however, there emerge exotic electronic orders induced by Kondo effect. The orbital Kondo effect can collectively make diagonal and off-diagonal (superconducting) orders. With the particle-hole symmetry in conduction bands, these orders are all degenerate, forming a macroscopic SO(5) multiplet. This paper discusses recent theoretical development on these electronic orders which are relevant to Pr 3+ and U 4+ systems with even number of f electrons per site. In the superconducting order, each conduction-electron pair is coupled with local degrees of freedom, forming a composite entity with a staggered spatial pattern. The quasi-particle spectrum is best interpreted as virtual hybridization with resonant states at the Fermi level. Possible order parameter for URu2Si2 in the hidden order state is discussed in the context of composite orders. Briefly discussed are related issues such as homogeneous odd-frequency pairing and SO(5) theory for high-temperature superconductors.

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

Cited by 6 publications

References 25 publications

Electronic Order with Staggered Kondo and Crystalline Electric Field Singlets

Electronic Order with Staggered Kondo and Crystalline Electric Field Singlets

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

Composite electronic orders induced by orbital Kondo effect

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