Quantum field theory of metallic spin glasses

Abstract

We introduce an effective field theory for the vicinity of a zero temperature quantum transition between a metallic spin glass (``spin density glass'') and a metallic quantum paramagnet. Following a mean field analysis, we perform a perturbative renormalization-group study and find that the critical properties are dominated by static disorder-induced fluctuations, and that dynamic quantum-mechanical effects are dangerously irrelevant. A Gaussian fixed point is stable for a finite range of couplings for spatial dimensionality $d > 8$, but disorder effects always lead to runaway flows to strong coupling for $d \leq 8$. Scaling hypotheses for a {\em static\/} strong-coupling critical field theory are proposed. The non-linear susceptibility has an anomalously weak singularity at such a critical point. Although motivated by a perturbative study of metallic spin glasses, the scaling hypotheses are more general, and could apply to other quantum spin glass to paramagnet transitions.Comment: 16 pages, REVTEX 3.0, 2 postscript figures; version contains reference to related work in cond-mat/950412

Quantum charge glasses of itinerant fermions with cavity-mediated long-range interactions

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Dynamical study of the disordered quantump=2spherical model

“…Note added in proof: Recently, we learned of earlier studies [32] of the critical behavior of quantum rotors at finite dissipation. In the relevant parameter regime our results are qualitatively similar.…”

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

“…In CeCoIn 5 , the resistivity ρ(T ) − ρ 0 was found to be linear in T above the superconducting transition and up to pressures of 1.6 GPa [154]. Such behavior is expected for 2D antiferromagnetic quantum-critical system [44] and leads to the proposal that CeCoIn 5 is near an AFM QCP situated at slightly negative pressures [154]. At higher pressure, a FL-like resistivity ρ(T ) − ρ 0 ∼ T 2 is recovered between T c and a cross-over temperature T FL ( 2.5 K), whereas above T FL and up to 60 K, ρ(T ) − ρ 0 ∼ T 1.5 is observed.…”

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