Magnetic-Field Control of Quantum Critical Points of Valence Transition

Abstract

We study the mechanism of how critical end points of first-order valence transitions are controlled by a magnetic field. We show that the critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field, and unexpectedly, the QCP exhibits nonmonotonic field dependence in the ground-state phase diagram, giving rise to the emergence of metamagnetism even in the intermediate valence-crossover regime. The driving force of the field-induced QCP is clarified to be cooperative phenomena of the Zeeman and Kondo effects, which create a distinct energy scale from the Kondo temperature. This mechanism explains the peculiar magnetic response in CeIrIn(5) and the metamagnetic transition in YbXCu(4) for X=In as well as the sharp contrast between X=Ag and Cd.

Magnetic and Electronic Quantum Criticality in YbRh2Si2

“…[35] should become apparent in our study of YbRh 2 Si 2 under positive and negative chemical pressure. Second, no signature of a first order transition appears under pressure as expected for a critical end point of a valence transition that might give rise to a QCP [36]. In addition, this absence of a first order transition seems to rule out a quantum tricritical point as the origin of the quantum criticality [37].…”

T/B Scaling in β-YbAlB4

“…21, the location of the QCP in the ground-state phase diagram in the ε f -U fc plane is moved by applying h. If the system is located in the vicinity of the QCP at h = 0, applying h moves the system away from the QCP, which causes the marked suppression of χ at large h. In this Letter, we discussed the h-dependence of χ through the h-dependence of η 0σ and v 4σ with the QCP being unmoved for simplicity of analysis. Taking account of this effect is expected to make the crossover T/h between the Fermi liquid and non-Fermi liquid regimes shift to the larger-T/h direction in Fig.…”

New universality class of quantum criticality in Ce- and Yb-based heavy fermions

“…1, the CEP at negative temperatures is moved up toward the T > 0 direction by applying a magnetic field, giving rise to an emergence of the QCEP [35]. Namely, it has been shown that the CEP is induced to emerge from the negative temperature side to the positive temperature side by applying a magnetic field in the valence-crossover regime [34,36]. Correspondence between the phase diagram in Fig.…”

“…As shown in ref. [36], uniform magnetic susceptibility diverges at the QCEP where valence fluctuation diverges. This is due to the fact that χ v (q, iω l ) and the dynamical f-spin susceptibility χ(q, iω l ) =…”

“…(3) gives logarithmic energy dependence in the real part of the self-energy [42]. A numerical solution of the self-energy gives logarithmic temperature dependence in the specific-heat coefficient C/t ∼ −logt even for the temperature regime for T > T 0 where the uniform magnetic susceptibility and the resistivity behave as χ(t) ∼ t −α with 0.5 < ∼ α < ∼ 0.7 and ρ(t) ∼ t, respectively [36]. Anomalous temperature dependence of the specific-heat coefficient and the resistivity of our theory shares an aspect similar to that based on the marginal Fermi liquid (MFL) assumption for high-T c cuprates [40,41], in which the self-energy is given by Σ(ε) ∝ ε (ln ε − i|ε|).…”