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Register a new userEnhanced antiferromagnetic ordering tendency in staggered periodic Anderson model
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Mi Jiang
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Heavy fermion compounds consisting of two or more inequivalent local moment sites per unit cell have been a promising platform of investigating the interplay between distinct Kondo screenings that is absent in the conventional systems containing only one rare-earth ion per unit cell. We report a remarkable enhancement of the antiferromagnetic (AF) ordering tendency in the staggered periodic Anderson model (PAM) with two alternating inequivalent local moments if their hybridization strengths reside in the Kondo singlet and antiferromagnetic insulator regime separately of the phase diagram of homogeneous PAM. Our results uncover the rich physics induced by the interplay of multiple energy scales in the staggered PAM and furthermore implies the ubiquitous existence of the enhancement of physical quantities in general inhomogeneous systems.
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Whether or not a physical property can be enhanced in an inhomogeneous system compared with its homogeneous counterpart is an intriguing fundamental question. We provide a concrete example with positive answer by uncovering a remarkable enhancement of both antiferromagnetic (AF) structure factor and $d$-wave pairing tendency in the doped staggered periodic Anderson model (PAM) with two alternating inequivalent local moments. The common thread of these enhancement is found to originate from the generic self-averaging effect and non-monotonic dependence of the corresponding physical quantity in homogeneous PAM. More strikingly, we provided evidence of the coexistence of these two enhancement via a tentative phase diagram. Our findings may imply the plausible generalization of enhancing physical properties in generic inhomogeneous systems.
A central feature of the Periodic Anderson Model is the competition between antiferromagnetism, mediated by the Ruderman-Kittel-Kasuya-Yosida interaction at small conduction electron-local electron hybridization $V$, and singlet formation at large $V$. At zero temperature, and in dimension $d>1$, these two phases are separated by a quantum critical point $V_c$. We use Quantum Monte Carlo simulations to explore the effect of impurities which have a local hybridization $V_{*} < V_c$ in the AF regime which are embedded in a bulk singlet phase with $V > V_c$. We measure the suppression of singlet correlations and the antiferromagnetic correlations which form around the impurity, as well as the size of the resulting domain. Our calculations agree qualitatively with NMR measurements in CeCoIn$_{5-x}$Cd$_x$.
Recently, dynamical mean field theory calculations have shown that kinks emerge in the real part of the self energy of strongly correlated metals close to the Fermi level. This gives rise to a similar behavior in the quasi-particle dispersion relation as well as in the electronic specific heat. Since f-electron systems are even more strongly correlated than the -hitherto studied- d-electron systems we apply the dynamical mean field approach with the numerical renormalization group method as impurity solver to study whether there are kinks in the periodic Anderson model.
The Kondo and Periodic Anderson Model (PAM) are known to provide a microscopic picture of many of the fundamental properties of heavy fermion materials and, more generally, a variety of strong correlation phenomena in $4f$ and $5f$ systems. In this paper, we apply the Determinant Quantum Monte Carlo (DQMC) method to include disorder in the PAM, specifically the removal of a fraction $x$ of the localized orbitals. We determine the evolution of the coherence temperature $T^*$, where the local moments and conduction electrons become entwined in a heavy fermion fluid, with $x$ and with the hybridization $V$ between localized and conduction orbitals. We recover several of the principal observed trends in $T^*$ of doped heavy fermions, and also show that, within this theoretical framework, the calculated Nuclear Magnetic Resonance (NMR) relaxation rate tracks the experimentally measured behavior in pure and doped CeCoIn$_5$. Our results contribute to important issues in the interpretation of local probes of disordered, strongly correlated systems.
We investigate an extended version of the periodic Anderson model where an interaction is switched on between the doubly occupied d- and f-sites. We perform variational calculations using the Gutzwiller trial wave function. We calculate the f-level occupancy as a function of the f-level energy with different interaction strengths. It is shown that the region of valence transition is sharpened due to the new interaction.
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