Critical spin and charge fluctuations accompanying Kondo destruction in the particle-hole asymmetric Bose-Fermi Anderson model

Metallic quantum criticality is a central theme in a variety of strongly correlated systems. Recent experiments point to the puzzling existence of a singular charge response in heavy-fermion settings where the Landau framework of order-parameter fluctuations allows singularity only in the spin channel. A possible explanation lies in the Kondo-destruction scenario for beyond-Landau quantum criticality, which incorporates additional critical degrees of freedom [1-3]. Fluctuations between “large” and “small” Fermi surfaces lead to complete loss of quasiparticles in the quantum-critical regime. Here, we survey critical responses accompanying Kondo destruction in Bose-Fermi Anderson impurity models with a power-law bosonic bath having an exponent s < 1, and with a fermionic density of states that either vanishes at the Fermi energy as ρ(ε) ∝ |ε - ε_F|^r with r > 0 or is featureless (corresponding to r = 0). We examine the nature of the critical fluctuations for different combinations of r and s, and compare the energy scales for fluctuations in the spin and charge channels.

[1] Q. Si et al., Nature 413, 804 (2001).

[2] P. Coleman et al., J. Phys. Condens. Matt. 13, R723 (2001).

[3] T. Senthil et al., Phys. Rev. B 69, 035111 (2004).