Theory of charge transport in molecular junctions: From Coulomb blockade to coherent tunneling

Abstract

We study charge transport through molecular junctions in the presence of electron-electron interaction using the nonequilibrium Green's function techniques and the renormalized perturbation theory. In the perturbation treatment, the zeroth-order Hamiltonian of the molecular junction is composed of independent single-impurity Anderson's models, which act as the channels where charges come through or occupy, and the interactions between different channels are treated as the perturbation. Using this scheme, the effects of molecule-lead, electron-electron, and hopping interactions are included nonperturbatively, and the charge transport processes can thus be studied in the intermediate parameter range from the Coulomb blockade to the coherent tunneling regimes. The concept of quasi-particles is introduced to describe the kinetic process of charge transport, and then the electric current can be studied and calculated. As a test study, the Hubbard model is used as the molecular Hamiltonian to simulate dimeric and trimeric molecular junctions. Various nonlinear current-voltage characteristics, including Coulomb blockade, negative differential resistance, rectification, and current hysteresis, are shown in the calculations, and the mechanisms are elucidated.

Time evolution of nanoscale systems by finite difference method

“…Investigating charge transport in molecular junctions has been interesting for scientists [1,[23][24][25][26]. Electrical transport properties of a system have a closed relation to the time evolution of the charge density in it.…”

Unconventional photon blockade from bimodal driving and dissipations in coupled semiconductor microcavities

“…A conventional photon blockade requires enhanced resonant nonlinearities [21][22][23], and has similar principles to the Rydberg blockade [24], the Coulomb blockade [25][26][27][28], the spin blockade [29,30], quantum optomechanical systems [31][32][33][34][35][36][37][38][39], polaritons [40], cavity quantum electrodynamics [41][42][43][44][45][46], two-level systems coupled to a cavity [47] and cavity-coupled four-level quantum emitters [48]. A lot of work has been accomplished on nanostructured cavities and semiconductor microcavities with second-order nonlinearities [49][50][51].…”

Thermally induced charge current through long molecules

“…In general, thermoelectric charge transport through molecular junctions is controlled by simultaneous driving by electric and thermal driving forces. The combined effect of these forces depends on several factors including the bridge geometry and the characteristics of its coupling to the leads [13][14][15][16][17][18][19][20][21][22][23][24] and electron-electron interactions [25][26][27][28][29][30][31][32][33][34]. Thermoelectric transport characteristics may be affected due to interaction between transmitting electrons and environmental nuclear motions [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] and the effects of quantum interference [55,56].…”