Towards high-temperature coherence-enhanced transport in heterostructures of a few atomic layers

Abstract

The possibility to exploit quantum coherence to strongly enhance the efficiency of charge transport in solid state devices working at ambient conditions would pave the way to disruptive technological applications. In this work, we tackle the problem of the quantum transport of photogenerated electronic excitations subject to dephasing and on-site Coulomb interactions. We show that the transport to a continuum of states representing metallic collectors can be optimized by exploiting the "superradiance" phenomena. We demonstrate that this is a coherent effect which is robust against dephasing and electron-electron interactions in a parameters range that is compatible with actual implementation in few monolayers transition-metal-oxide (TMO) heterostructures.

Electric-field assisted optimal quantum transport of photo-excitations in polar heterostructures

“…ST as shown for γ φ = 0, E 0 Ẽ 0 in Fig. 6, and as was established in [3] for E 0 = 0, γ φ γ φ ≈ 4Ω/N . In addition we find two additional optimal parameters as shown in Fig.…”

“…The initial state is a Gaussian state Eq. 9 with ∆ 0 = 0, n 0 = 3, k 0 = 0. the average transfer time is always minimized at the ST [9,3], γ out = γ ST ≈ 2Ω . In this figure, as vertical dashed line, we indicate the "critical" electric po-tentialẼ 0 = 4 √ 2Ω/N derived below, see Eq.…”

“…However, in contrast to the superradiance from the coupling to the sink (i.e. ST in the opening) [3], this does not lead to fast quantum coherent transport as we will demonstrate below.…”

“…The starting point of our approach, already introduced in Ref. [3], is to model the interlayer transport by the single-excitation manifold of a one dimensional N-site chain of two-level systems, which represent the photo-excitation across the gap of the TMO. The many-body interactions, which lead to the effective broadening of the electronic levels, are accounted for by a dephasing term that tends to suppress quantum transport.…”

“…Recently it was discussed that with proper engineering of the collector properties, the system can be tuned to the superradiant transition which gives rise to fast quantum coherent transport in thin films made of few TMO monolayers [3]. This effect was shown to be robust against realistic estimates of electron-electron correlations [3] and to environment induced dephasing up to ambient temperatures. The effect of the intrinsic electric potential gradient was taken into account only insofar as a shift of the Fermi-level of the collector as is common in the Landauer-Büttiker [4,5,6] and the master equation [7] approaches to transport.…”