Quantum criticality in the spin-isotropic pseudogap Bose-Fermi Kondo model: Entropy, scaling, and the 
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-theorem

Yu, Zuodong; Zamani, Farzaneh; Ribeiro, Pedro; Kirchner, Stefan

doi:10.1103/physrevb.102.115124

Cited by 5 publications

(6 citation statements)

References 69 publications

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“…7 (c,d). One can clearly see the Lyapunov exponent is indeed monotonically decreasing as increasing g, and is finally vanishing at finite g. This monotonous behavior is consistent with the result that residual entropy for this model increases monotonously from M CK phase to LM ′ phase 40 . This behavior of residual entropy voilate the g-theorem which demand the entropy should decrease along RG trajectories if conformal invariance is presented.…”

Section: Numerical Resultssupporting

confidence: 88%

“…We also observe the system has no butterfly effect below a typical Kondo coupling J K for finite temperature. When coupled to bosonic bath, the monotonously decrease of λ L do not obey general argument that the highest chaotic behavior occurs at the quantum critical point, but is consistent with the behav-ior of impurity entropy and violation of g-theorem in the model 40 . Appendix C: Bethe-Salpeter equation at the low temperature limit…”

Section: Discussionmentioning

confidence: 71%

“…Tπ /D=0.1 Now we introduce the coupling between impurity and bosonic bath g. By increasing g, the systems will go through the overscreened multichannel Kondo phase to a critical local moment phase which is separated by a unstable fixed point 32,33,35,40 with critical coupling g c . Generally near the quantum critical point, the non-Fermi liquid will arise and the conformal symmetry emerges, leading to the larger chaotic behavior with λ L ∼ T than other regions away from critical point 29 .…”

Section: Numerical Resultsmentioning

confidence: 99%

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Quantum Chaos of the Bose-Fermi Kondo model at the intermediate temperature

Han,

2021

Preprint

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We study the quantum chaos in the Bose-Fermi Kondo model in which the impurity spin interacts with conduction electrons and a bosonic bath at the intermediate temperature in the large N limit. The out-of-time-ordered correlator is calculated based on the Bethe-Salpeter equation and the Lyapunov exponent λL is extracted. Our calculation shows that the Lyapunov exponent monotonically increases as the Kondo coupling JK increases, and it can reach an order of λL ∼ T as JK approaches the M CK point. Furthermore, we also demonstrate that λL decreases monotonously as the impurity and bosonic bath coupling g increases, which is contrary to the general expectation that the most chaotic property occurs at the quantum critical point with the non-Fermi liquid nature.

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Section: Numerical Resultssupporting

confidence: 88%

Section: Discussionmentioning

confidence: 71%

Section: Numerical Resultsmentioning

confidence: 99%

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Quantum Chaos of the Bose-Fermi Kondo model at the intermediate temperature

Han,

2021

Preprint

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“…In this section, we show that the field c l1,...,ln−1,α,i,µ ( µ ) defined in equation ( 9) of the main text and the field Φ 0,...,0,α,i ( ) defined in equation (10) of the main text are fermionic fields satisfying the proper anticommutation relations. Due to the delta function identity…”

Section: (A26)mentioning

confidence: 92%

“…1(a)). Although this treatment works well for normal metals with well-defined Fermi surfaces, it will encounter difficulties in more exotic thermals baths, including the pseudogapped systems 10 and those with Fermi points, such as topological semimetals.…”

Section: Introductionmentioning

confidence: 99%

Exact solutions of Kondo problems in higher-order fermions

Song,

Ma,

Wang

et al. 2022

Preprint

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The conformal field theory (CFT) approach to Kondo problems, originally developed by Affleck and Ludwig (AL), has greatly advanced the fundamental knowledge of Kondo physics. The CFT approach to Kondo impurities is based on a necessary approximation, i.e., the linearization of the low-lying excitations in a narrow energy window about the Fermi surface. This treatment works well in normal metal baths, but encounters fundamental difficulties in systems with Fermi points and high-order dispersion relations. Prominent examples of such systems are the recently-proposed topological semimetals with emergent higher-order fermions. Here, we develop a new CFT technique that yields exact solutions to the Kondo problems in higher-order fermion systems. Our approach does not require any linearization of the low-lying excitations, and more importantly, it rigorously bosonizes the entire energy spectrum of the higher-order fermions. Therefore, it provides a more solid theoretical base for evaluating the thermodynamic quantities at finite temperatures. Our work significantly broadens the scope of CFT techniques and brings about unprecedented applications beyond the reach of conventional methods.

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Quantum chaos of the Bose-Fermi Kondo model at intermediate temperature

Han

2021

Phys. Rev. B

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Quantum criticality in the spin-isotropic pseudogap Bose-Fermi Kondo model: Entropy, scaling, and the g -theorem

Cited by 5 publications

References 69 publications

Quantum Chaos of the Bose-Fermi Kondo model at the intermediate temperature

Quantum Chaos of the Bose-Fermi Kondo model at the intermediate temperature

Exact solutions of Kondo problems in higher-order fermions

Quantum chaos of the Bose-Fermi Kondo model at intermediate temperature

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