Junctions of one-dimensional quantum wires - correlation effects in transport

We study transport properties of quantum impurity systems using the functional renormalization group. The latter is an RG-based diagrammatic tool to treat Coulomb interactions in a fast and flexible way. Prior applications, which employed a simple first-order (Hartree-Fock-like) scheme to truncate the FRG flow equations within the Matsubara formalism, succeeded in accurately describing linear transport of various quantum dot geometries at zero temperature T=0. In a nutshell, ...

We investigate the effect of electron-electron interactions on the transport properties of disordered quasi one-dimensional quantum wires with two or more subbands occupied. We apply two alternative methods to solve the logarithmic divergent problem, namely the parquet graph theory and a renormalization group calculation. We solve the group equations analytically in the weak coupling limit and find a power-law for the temperature dependent conductivity of a multi-channel syst...

In this work we present a theoretical study of transport properties of a double crossbar junction composed by segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green's function formalism using real space renormalization techniques. We show calculations of the local density of states, linear conductance and I-V characteristics. Our results depict a resonant b...

We study the Kondo and transport properties of a quantum dot with a single magnetic Mn ion connected to metallic leads. By employing a numerical renormalization group technique we show that depending on the value of ferromagnetic coupling strength between the local electronic spin and the magnetic moment of the Mn, two distinct Kondo regimes exist. In the weak coupling limit, the system can be found in a completely screened Kondo state describing a local magnetic moment decou...

It is well known that the pristine bulk of an interacting one-dimensional system in Tomonaga-Luttinger liquid (TLL) phase shows power law suppression of quasi-particle tunneling amplitude for all values of TLL parameter $g$, in the zero energy limit. We perform a density matrix renormalization group (DMRG) study of a fully symmetric Y junction of TLL wires and observe an anomalous enhancement of the tunneling density of states (TDOS) in the vicinity of the junction for both (...

We present a theoretical study of correlated atomic wires deposited on substrates in two parts. In this first part, we propose lattice models for a one-dimensional quantum wire on a three-dimensional substrate and map them onto effective two-dimensional lattices using the Lanczos algorithm. We then discuss the approximation of these two-dimensional lattices by narrow ladder models that can be investigated with well-established methods for one-dimensional correlated quantum sy...

We introduce an equilibrium formulation of the functional renormalization group (fRG) for inhomogeneous systems capable of dealing with spatially finite-ranged interactions. In the general third order truncated form of fRG, the dependence of the two-particle vertex is described by O(N^4) independent variables, where N is the dimension of the single-particle system. In a previous paper [Phys. Rev. B 89, 045128 (2014)], the so-called coupled-ladder approximation (CLA) was intro...

We investigate the transport properties of a (small) quantum dot connected to Fermi liquid leads with a power-law density of states (DOS). Such a system, if experimentally realizable, will have interesting physical properties including: (i) non-saturating Coulomb blockade peak widths; (ii) a non-unitary Kondo peak symmetrically placed between the Coulomb blockade peaks; (iii) an absence of conductance away from particle-hole symmetry at sufficiently low temperatures; and (iv)...

A theory of thermal transport in a two-channel Kondo system, such as the one formed by a small quantum dot coupled to two leads and to a larger dot, is formulated. The interplay of the two screening constants allows an exploration of the Fermi liquid and non-Fermi liquid regimes. By using analytical, as well as numerical renormalization group methods, we study the temperature dependence of the thermal conductance and the Lorentz number. We find that in the low temperature lim...

The transport properties of a double quantum-dot device with one of the dots coupled to perfect conductors are analyzed using the numerical renormalization group technique and slave-boson mean-field theory. The coupling between the dots strongly influences the transport through the system leading to a non-monotonic dependence of the conductance as a function of the temperature and the magnetic field. For small inter-dot coupling and parameters such that both dots are in the K...