Sunhee Lee

Objective:

• Using NEMO 3-D, implement and investigate exchange splitting of 2-electron system of double dot system used for qubits
• Find out relationship between inter-dot distance and exchange splitting

Approach

• Use the spds* tight binding (TB) band model
• Potential is modeled as a quadratic function
• For initial cut, use Heitler-London approximation assuming that the coupling of the electron wavefunction is small
• Compare with other analytical result, such as HL and Hund-Mulliken(HM) approximation

Results & Impact:

• Depending on the inter-dot distance, the exchange splitting exponentially decays
• Reasonable agreement with analytical solutions

Ongoing Work:

• Self-consistent simulation with Configuration Interaction (CI) calculation

Device geometry for simulation

• Assumed 104.3x104.3x3.3nm3 Si structure (1.7MA) from (arxiv:0906.4793v2)

Results