Finite-bias conductance anomalies at a singlet-triplet crossing

TY - JOUR

T1 - Finite-bias conductance anomalies at a singlet-triplet crossing

AU - Stevanato, Chiara

AU - Leijnse, Martin Christian

AU - Flensberg, Karsten

AU - Paaske, Jens

N1 - [QDev]

PY - 2012/10/16

Y1 - 2012/10/16

N2 - 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. The effect remains entirely general and should be observable in a wide range of Coulomb blockaded devices.

AB - 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. The effect remains entirely general and should be observable in a wide range of Coulomb blockaded devices.

U2 - 10.1103/PhysRevB.86.165427

DO - 10.1103/PhysRevB.86.165427

M3 - Journal article

SN - 2469-9950

VL - 86

SP - 165427

JO - Physical Review B

JF - Physical Review B

IS - 16

ER -