ABSTRACT
Semiconductor quantum dots are often referred to as artificial atoms since they contain well-defined discrete levels. When two of these quantum dots are coupled, bonding and anti-bonding states are formed, analogous to covalent diatomic molecules. We use microwaves to excite an electron from the bonding to the anti-bonding state and measure a photonassisted-tunneling current through the quantum dot molecule. We can in-situ change the tunnel coupling and find a, clear transition from electrostatic (ionic) to covalent coupling in a double-quantum-dot system.
