2007/06/27 by M. Sindel, L. Borda, J. Martinek +9 · 70 citations
Engineering · Physics and Astronomy · #Advancements in Semiconductor Devices and Circuit Design #Condensed matter physics #Density of states #Electron #Kondo effect #Kondo insulator #Physics #Quantum and electron transport phenomena #Quantum dot #Quantum mechanics #Semiconductor materials and devices #Spin polarization #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.76.045321
published in Physical Review B 76(4) (American Physical Society) · 18 pages, 18 figures, accepted for publication in PRB
arxiv created 2007/06/27 · openalex publication_date 2007/07/18 · arxiv updated 2011/11/09 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We systematically study the influence of ferromagnetic leads on the Kondo resonance in a quantum dot tuned to the local moment regime. We employ Wilson's numerical renormalization group method, extended to handle leads with a spin asymmetric density of states, to identify the effects of (i) a finite spin polarization in the leads (at the Fermi surface), (ii) a Stoner splitting in the bands (governed by the band edges), and (iii) an arbitrary shape of the lead density of states. For a generic lead density of states, the quantum dot favors being occupied by a particular spin species due to exchange interaction with ferromagnetic leads, leading to suppression and splitting of the Kondo resonance. The application of a magnetic field can compensate this asymmetry, restoring the Kondo effect. We study both the gate voltage dependence (for a fixed band structure in the leads) and the spin polarization dependence (for fixed gate voltage) of this compensation field for various types of bands. Interestingly, we find that the full recovery of the Kondo resonance of a quantum dot in the presence of leads with an energy-dependent density of states is possible not only by an appropriately tuned external magnetic field but also via an appropriately tuned gate voltage. For flat bands, simple formulas for the splitting of the local level as a function of the spin polarization and gate voltage are given.