Finite-bias conductance anomalies at a singlet-triplet crossing
arXiv:1207.3020 · doi:10.1103/PhysRevB.86.165427
Abstract
Quantum dots and single-molecule transistors may exhibit level crossings induced by tuning external parameters such as magnetic field or gate voltage. For Coulomb blockaded devices, this shows up as an inelastic cotunneling threshold in the differential conductance, which can be tuned to zero at the crossing. Here we show that, in addition, level crossings can give rise to a nearly vertical step-edge, ridge or even a Fano-like ridge-valley feature in the differential conductance inside the relevant Coulomb diamond. We study a gate-tunable quasidegeneracy between singlet and triplet ground states, and demonstrate how these different shapes may result from a competition between nonequilibrium occupations and weak (spin-orbit) mixing of the states. Our results are shown to be in qualitative agreement with recent transport measurements on a Mn complex [E. A. Osorio, et al., Nano Lett. 10, 105 (2010)]. The effect remains entirely general and should be observable in a wide range of Coulomb blockaded devices.
8 pages, 6 figures. Published version
References in corpus (6)
- Quantum phase transition in a single-molecule quantum dot
- Direct Measurement of the Spin-Orbit Interaction in a Two-Electron InAs Nanowire Quantum Dot
- Electric-field controlled spin reversal in a quantum dot with ferromagnetic contacts
- Kinetic Equations for Transport Through Single-Molecule Transistors
- Hybrid superconductor-semiconductor devices made from self-assembled SiGe nanocrystals on silicon
- Nonequilibrium Singlet-Triplet Kondo Effect in Carbon Nanotubes