2014/05/28 by David E. Logan, Adam P. Tucker, Adam Tucker +1 · 28 citations
Physics and Astronomy · #Condensed matter physics #Degenerate energy levels #Fermi liquid theory #Luttinger liquid #Phase transition #Physics #Physics of Superconductivity and Magnetism #Pseudogap #Quantum #Quantum and electron transport phenomena #Quantum critical point #Quantum mechanics #Quantum phase transition #Quantum phases #Semiconductor Quantum Structures and Devices #Spin (aerodynamics) #Superconductivity #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.90.075150
published in Physical Review B 90(7) (American Physical Society) · 27 pages, 7 figures
arxiv created 2014/05/28 · openalex publication_date 2014/08/28 · arxiv updated 2014/11/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study correlated quantum impurity models that undergo a local quantum phase transition (QPT) from a strong coupling, Fermi liquid phase to a non-Fermi liquid phase with a globally doubly degenerate ground state. Our aim is to establish what can be shown exactly about such ``local moment'' (LM) phases, of which the permanent (zero-field) local magnetization is a hallmark, and an order parameter for the QPT. A description of the zero-field LM phase is shown to require two distinct self-energies, which reflect the broken symmetry nature of the phase and together determine the single self-energy of standard field theory. Distinct Friedel sum rules for each phase are obtained, via a Luttinger theorem embodied in the vanishing of appropriate Luttinger integrals. By contrast, the standard Luttinger integral is nonzero in the LM phase but found to have universal magnitude. A range of spin susceptibilites are also considered, including that corresponding to the local order parameter, whose exact form is shown to be RPA-like, and to diverge as the QPT is approached. Particular attention is given to the pseudogap Anderson model, including the basic physical picture of the transition, the low-energy behavior of single-particle dynamics, the quantum critical point itself, and the rather subtle effect of an applied local field. A two-level impurity model that undergoes a QPT (``singlet-triplet'') to an underscreened LM phase is also considered, for which we derive on general grounds some key results for the zero-bias conductance in both phases.