Phase transitions in the pseudogap Anderson and Kondo models: Critical dimensions, renormalization group, and local-moment criticality

Article

关键词: GAPLESS FERMI SYSTEMS;    MAGNETIC-IMPURITIES;    QUANTUM IMPURITY;    FIELD-THEORY;    DYNAMICS;    GAP;    BI2SR2CACU2O8+DELTA;    SUPERCONDUCTORS;    TEMPERATURE;    STATE;   

DOI  :  10.1103/PhysRevB.70.214427

来源: SCIE

【 摘 要 】

The pseudogap Kondo problem, describing quantum impurities coupled to fermionic quasiparticles with a pseudogap density of states rho(omega)proportional toparallel toomegaparallel to(r) shows a rich zero-temperature phase diagram, with different screened and free moment phases and associated transitions. We analyze both the particle-hole symmetric and asymmetric cases using renormalization group techniques. In the vicinity of r=0, which plays the role of a lower-critical dimension, an expansion in the Kondo coupling is appropriate. In contrast, r=1 is the upper-critical dimension in the absence of particle-hole symmetry, and here insight can be gained using an expansion in the hybridization strength of the Anderson model. As a by-product, we show that the particle-hole symmetric strong-coupling fixed point for r<1 is described by a resonant level model, and corresponds to an intermediate-coupling fixed point in the renormalization group language. Interestingly, the value r=1/2 plays the role of a second lower-critical dimension in the particle-hole symmetric case, and there we can make progress by an expansion performed around a resonant level model. The different expansions allow a complete description of all critical fixed points of the models and can be used to compute a variety of properties near criticality, describing universal local-moment fluctuations at these impurity quantum phase transitions.

【 授权许可】

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