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TT: Tiefe Temperaturen

TT 22: Transport - Nanoelectronics II: Quantum Dots and Wires, Point Contacts

TT 22.7: Talk

Monday, March 7, 2005, 15:30–15:45, TU H2053

Anomalous conductance of a spin-1 quantum dot — •Anna Posazhennikova¹ and Piers Coleman² — ¹TKM, Univarsitaet Karlsruhe, 76128, Germany — ²Center for Materials Theory, Rutgers University, Piscataway, NJ 08855, USA

We interpret the recent observation of a zero-bias anomaly in spin-1 quantum dots in terms of an underscreened Kondo effect. Although a spin-1 quantum dots are expected to undergo a two-stage quenching effect, in practice the log normal distribution of Kondo temperatures leads to a broad temperature region dominated by underscreened Kondo physics. General arguments, based on the asymptotic decoupling between the partially screened moment and the leads, predict a singular temperature and voltage dependence of the conductance and differential conductance. Using a Schwinger boson approach, we show how these qualitative expectations are borne out in a detailed many body calculation.