Coherent versus Sequential Electron Tunneling in Quantum Dots

Manifestations of quantum coherence in the electronic conductance through nearly closed quantum dots in the Coulomb-blockade regime are addressed. We show that quantum coherent tunneling processes explain some puzzling statistical features of the conductance peak heights observed in recent experiments at low temperatures. We employ the constant interaction model and the random matrix theory to model the quantum dot electronic interactions and its single-particle statistical fluctuations, taking full account of the finite decay width of the quantum dot levels.

Figure 1

Peak height probability distribution $P(g^{\mathrm{m}\mathrm{a}\mathrm{x}})$ for $k_{B}T=0.1\Delta$ and $B\ne 0$ ($\beta =2$). The same for $B=0$ ($\beta =1$) in the inset. Our theory for $⟨\Gamma ⟩/\Delta =0.1$ (solid line) and 0.2 (dashed line) is compared with the standard sequential tunneling result (dotted line), and the experimental distribution (histogram) [1].

Figure 2

Normalized peak heights distribution width ${\sigma }_g$ for $B\ne 0$ (the $B=0$ case is shown in the inset) as a function of $k_{B}T/\Delta$, for $⟨\Gamma ⟩/\Delta =0.05,0.1,0.2$ (dash-dotted, solid, and dashed lines, respectively). Symbols correspond to the experimental results of Ref. 1 for different dots and the dotted lines to the standard sequential theory.

Figure 3

Normalized change in the average conductance $\alpha$ as a function of temperature for different $⟨\Gamma ⟩/\Delta$.