Composite Orders and Lifshitz Transition of Heavy Electrons

Abstract

Magnetic and other unconventional electronic orders are discussed for heavy electrons. In addition to the ordinary Kondo lattice, we consider non-Kramers systems taking the two-channel Kondo lattice, and another lattice that consists of a singlet-triplet f2 configuration. The latter gives a scalar order with staggered sublattices of crystalline-electric-field (CEF) and Kondo singlets, which accounts for the observed order in PrFe4P12. In the two-channel Kondo lattice, an odd-frequency pairing is realized that becomes degenerate at half-filling with a composite order involving both localized and conduction electrons. The degeneracy is interpreted in terms of a hidden SO(5) symmetry. For the ordinary Kondo lattice with exchange interaction J, we take insulating ground states as reference. The metallic states are approached by infinitesimal doping of carriers either from the Kondo insulator or from the antiferromagnetic insulator. By adding intersite exchange we find that location of the band extremum of the heavy band depends on the value of J. The change of J gives topological change of the Fermi surface, which corresponds to a generalized version of the Lifshitz transition, and occurs separately from the quantum critical point of the antiferromagnetic order.Comment: 8 pages, 5 figures, presentation at SCES2013 conferenc

Localized-to-itinerant transition preceding antiferromagnetic quantum critical point and gapless superconductivity in CeRh0.5Ir0.5In5

“…In passing, we mention a possibility of a more general case, a Lifshitz transition. Watanabe and Ogata 54 , and Kuramoto et al 55 pointed out that, even though the Kondo screening remains, a competition between the Kondo effect and the RKKY interaction can lead to a topological Fermi surface transition (Lifshitz transition) below the AF QCP 54,55 , which is also consistent with our observation.…”

Unconventional and conventional quantum criticalities in CeRh0.58Ir0.42In5

“…A Lifshitz transition, which does reconstruct the FS, under certain circumstances can produce a jump and sign change in S/T as a function of some non-thermal control parameter that tunes the chemical potential 37 or magnetic exchange. 38 Though these theoretical models 37,38 may capture aspects of our experimental observations, presently it is not possible to compare directly predictions of these models to our results as a function of pressure. In contrast to these plausible interpretations, evidence presented below allows a more straightforward and compelling interpretation of our observations within the framework of quantum criticality.…”

Unconventional and conventional quantum criticalities in CeRh$_{0.58}$Ir$_{0.42}$In$_5$

“…Though these theoretical models [37,38] may capture aspects of our experimental observations, presently it is not possible to compare directly predictions of these models to our results as a function of pressure. In contrast to these plausible interpretations, evidence presented below allows a more straightforward and compelling interpretation of our observations within the framework of quantum criticality.…”

“…Finally, we consider the possibility that a Lifshitz transition might account for transport and thermopower behaviors near p c1 . A Lifshitz transition, which does reconstruct the Fermi surface, under certain circumstances can produce a jump and sign change in S/T as a function of some nonthermal control parameter that tunes the chemical potential [37] or magnetic exchange [38].…”