Title: Functional renormalization group study of parallel double quantum dots: Effects of asymmetric dot-lead couplings,
Abstract: We explore the effects of asymmetry of hopping parameters between double
parallel quantum dots and the leads on the conductance and a possibility of
local magnetic moment formation in this system using functional renormalization
group approach with the counterterm. We demonstrate a possibility of a quantum
phase transition to a local moment regime (so called singular Fermi liquid
(SFL) state) for various types of hopping asymmetries and discuss respective
gate voltage dependences of the conductance. It is shown, that depending on the
type of the asymmetry, the system can demonstrate either a first order quantum
phase transition to SFL state, accompanied by a discontinuous change of the
conductance, similarly to the symmetric case, or the second order quantum phase
transition, in which the conductance is continuous and exhibits Fano-type
asymmetric resonance near the transition point. A semi-analytical explanation
of these different types of conductance behavior is presented.