Critical charge fluctuations in a pseudogap Anderson model

Chowdhury, Tathagata; Ingersent, Kevin

doi:10.1103/physrevb.91.035118

Cited by 13 publications

(14 citation statements)

References 30 publications

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“…3(a) and (b), c d approaches −U as v 0 → 0 and tends to approach − U 2 as v 0 → ∞. This dependence has been proposed elsewhere [48] but no quantitative calculation has been conducted until now. To understand this, one recalls that in conventional Kondo models, the Kondo scale depends strongly on the hybridization function around the Fermi level.…”

Section: Impurity On Top Of An Atommentioning

confidence: 77%

Phase diagram of a pseudogap Anderson model with application to graphene

Dang,

Nghiem

2021

Preprint

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The Anderson model of an s-wave single-orbital correlated impurity placed on a noninteracting honeycomb lattice, a simplified model for studying an impurity on graphene, is used to investigate pseudogap Kondo problem. In this model, there are two quantum phases: the phase of free impurity local moment and the Kondo phase where this local moment is fully screened. The transition between these two phases is under investigation. The work focuses mostly on the case where the impurity is placed on top of a lattice site. In this case, the full phase diagram is constructed using three parameters: the Hubbard interaction U , the hybridization strength v0 and the impurity energy level d . The phase diagram exhibits linear (U c , c d ) phase boundary, the slope of which, as well as the critical value c d , depends strongly on v 2 0 . Further analysis shows that the real part of the self energy at zero frequency and the impurity occupancy can help to understand the behaviors of the phase boundaries. The dependence of the phase transition on the impurity position is briefly discussed, revealing difficulties that one needs to solve in order to realize the pseudogap Kondo model in the realistic graphene lattice.In the experimental aspect, the pseudogap Kondo model has been used to interpret reasonably a new type of QCPs that occurs in heavy fermion systems [8,22,27] or to study impurity local moment in unconventional superconductors [28]. However, the difficulty in realizing the model in experiments is the main issue that hinders the progress of research in this topic. Indeed there

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Section: Impurity On Top Of An Atommentioning

confidence: 77%

Phase diagram of a pseudogap Anderson model with application to graphene

Dang,

Nghiem

2021

Preprint

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“…In a simple antiferromagnet, the particle-particle component of the spinon Green's function is where E q = λ 2 − ∆ 2 q , u = cosh θ q , v = sinh θ q and tanh 2θ q = −∆ q /λ. Substituting this into (29), we obtain…”

Section: The Leading Order Solutionmentioning

confidence: 99%

“…While Kondo Breakdown has been extensively modelled at an impurity-level [28,29] and simulated using dynamical mean-field theory [10,30,31], a possible link with charge fluctuations has not sofar been explored in the lattice. To examine this idea, we introduce a simple field-theoretic framework for Kondo breakdown, emplying a Schwinger boson representation of spins that permits us to treat Kondo screening and antiferromagnetism [32,33].…”

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confidence: 99%

Emergent Critical Charge Fluctuations at the Kondo Breakdown of Heavy Fermions

Komijani

Coleman

2019

Phys. Rev. Lett.

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One of the challenges in strongly correlated electron systems, is to understand the anomalous electronic behavior that develops at an antiferromagnetic quantum critical point (QCP), a phenomenon that has been extensively studied in heavy fermion materials. Current theories have focused on the critical spin fluctuations and associated break-down of the Kondo effect. Here we argue that the abrupt change in Fermi surface volume that accompanies heavy fermion criticality leads to critical charge fluctuations. Using a model one dimensional Kondo lattice in which each moment is connected to a separate conduction bath, we show a Kondo breakdown transition develops between a heavy Fermi liquid and a gapped spin liquid via a QCP with ω/T scaling, which features a critical charge mode directly associated with the break-up of Kondo singlets. We discuss the possible implications of this emergent charge mode for experiment. arXiv:1810.08148v2 [cond-mat.str-el]

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“…Now we investigate the influence of ph-symmetry breaking on the real-time dynamics. We recall that the asymmetric strong-coupling (ASC) fixed point [6][7][8]21,43] differs from the SC FP by a complete screen ing of the impurity spin independently of r. Furthermore, the equilibrium double occupancy (D)eq in the ASC FP depends on the asymmetry \U -2ed| and the band exponent r: With increasing asymmetry or increasing r the equilibrium double occupancy ((D)eq = 1/4 for ph symmetry) increases.…”

Section: Quenches With Particle-hole Asymmetrymentioning

confidence: 98%

Real-time dynamics induced by quenches across the quantum critical points in gapless Fermi systems with a magnetic impurity

2014

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The energy-dependent scattering of fermions from a localized orbital at an energy-dependent rate T(e) oc |£|r gives rise to quantum critical points (QCPs) in the pseudogap single-impurity Anderson model separating a local moment phase with an unscreened spin moment from a strong-coupling phase which slightly deviates from the screened phase of standard Kondo problem. Using the time-dependent numerical renormalization group (TD-NRG) approach we show that local dynamic properties always equilibrate towards a steady-state value even for quenches across the QCP but with systematic deviations from the thermal equilibrium depending on the distance to the critical coupling. Local nonequilibrium properties are presented for interaction quenches and hybridization quenches. We augment our numerical data by an analytical calculation that becomes exact at short times and find excellent agreement between the numerics and the analytical theory. For interaction quenches within the screened phase we find a universal function for the time-dependent local double occupancy. We trace back the discrepancy between our results and the data obtained by a time-dependent Gutzwiller variational approach to restrictions of the wave-function ansatz in the Gutzwiller theory: while the NRG ground states properly account for the formation of an extended spin moment which decouples from the system in the unscreened phase, the Gutzwiller ansatz only allows the formation of the spin moment on the local impurity orbital.

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Critical charge fluctuations in a pseudogap Anderson model

Cited by 13 publications

References 30 publications

Phase diagram of a pseudogap Anderson model with application to graphene

Phase diagram of a pseudogap Anderson model with application to graphene

Emergent Critical Charge Fluctuations at the Kondo Breakdown of Heavy Fermions

Real-time dynamics induced by quenches across the quantum critical points in gapless Fermi systems with a magnetic impurity

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