Transport and Optical Spectroscopy of an Array of Quantum Dots with Strong Coulomb Correlations

Abstract

Quantum dot devices which utilize the Coulomb blockade represent the limit of single-electronics: when gated in a three-terminal configuration, they can function as singleelectron transistors (Kastner, 1992); when driven at rf frequency f, they can function as electron pumps generating a current I=ef (Kouwenhoven et al., 1991). Arrays of small tunnel junctions have been used (Geerlings et al., 1990) to suppress coherent multipleelectron tunneling events (co-tunneling), which limit precise current quantization. Co- tunneling is a weak perturbation to incoherent transport in arrays of metal-oxide junctions, it is a process to be treated equally with capacitive energies in arrays of semiconducting quantum dots (Stafford and Das Sarma, 1994a). The Coulomb blockade of a single quantum dot coupled incoherently to its environment is replaced by collective phenomena arising from the interplay of quantum confinement, coherent interdot tunneling, and strong intradot Coulomb interactions. Quantum dot arrays provide ideal systems to study phase transitions (Stafford and Das Sarma, 1994a). Understanding the collective behavior in such systems will be crucial to model circuits of single-electonic devices in coherent quantum transport. Previously (Stafford and Das Sarma, 1994a), we considered a quantum mechanical capacitor formed by an array of dots within a parallel plate capacitor (Ashoori et al., 1993). Here, we calculate the conductance and far-infrared absorption of linear arrays of up to 10 dots using a generalized Hubbard model (Stafford and Das Sarma, 1994b).