Periodic Anderson model with electron-phonon correlated conduction band

Abstract

This paper reports dynamical mean field calculations for the periodic Anderson model in which the conduction band is coupled to phonons. Motivated in part by recent attention to the role of phonons in the $\gamma$-$\alpha$ transition in Ce, this model yields a rich and unexpected phase diagram which is of intrinsic interest. Specifically, above a critical value of the electron-phonon interaction, a first order transition with two coexisting phases develops in the temperature-hybridization plane, which terminates at a second order critical point. The coexisting phases display the familiar Kondo screened and local moment character, yet they also exhibit pronounced polaronic and bipolaronic properties, respectively.Comment: 4 pages, 6 figure

Periodic Anderson model with Holstein phonons for the description of the cerium volume collapse

“…Since the electron charge susceptibility is positively correlated with U ef f , the suppression of the electron-phonon coupling effect is also reflected in the decrease of the charge susceptibility as V increases for fixed β (not shown). As V increases from 0.1 to 1.8, the localized f electron moments that are present at small V get screened by the conduction electrons when V is large [31]. The screening of the localized f electron moments in the large V regime is a signature of the Kondo effect, which we can also observe by studying the f electron spectral functions.…”

“…With the parameters g and k, we construct the effective electron-phonon interaction strength, U ef f = g 2 2k . Throughout this paper and to be consistent with the experimental results, we have set Ω 0 = 0.01 [31] unless otherwise specified. To preserve the large temperature metallic phase, we fix the total electronic density at n = 1.8 by tuning the chemical potential at each iteration of the DMFT cycle.…”

“…This kind of models has not been extensively studied in the literature largely due to its complexity and its associated computational challenges. Our model is particularly challenging due to the fact that the correlations in the conduction band due to electronphonon coupling are retarded [31]. The competition and cooperation among the Kondo effect, the Ruderman-Kittel-Kasuya-Yosida interaction, and the correlation effect in the conduction band produces a very rich phase diagram [35][36][37].…”

“…In their study, the electronic part is modeled by a single impurity model. In this work, we use the periodic Anderson model with Holstein phonons coupled to the conduction band as our starting point [31]. We solve this model using the DMFT approximation with the continuous time quantum Monte Carlo as our impurity solver.…”

Superconducting Kondo phase in an orbitally separated bilayer

“…Indeed, such strategy has proved fruitful, for instance, in the case of Ce-based superlattices [26], and more recently in the twisted bilayer graphene [27,28], which revealed a wealth of interesting magnetic and superconducting phenomena. We should mention that proximity effects have been studied in the context of the Hubbard model in a layered geometry [29,30], resulting in an induced pairing in the adjacent layers; electron-phonon coupling could also provide the appearance of superconductivity in Kondo insulators, by combining the Holstein model with the PAM [31][32][33].…”