Cavity enhanced transport of excitons (1409.2550v3)

Abstract: We show that exciton-type transport in certain materials can be dramatically modified by their inclusion in an optical cavity: the modification of the electromagnetic vacuum mode structure introduced by the cavity leads to transport via delocalized polariton modes rather than through tunneling processes in the material itself. This can help overcome exponential suppression of transmission properties as a function of the system size in the case of disorder and other imperfections. We exemplify massive improvement of transmission for excitonic wave-packets through a cavity, as well as enhancement of steady-state exciton currents under incoherent pumping. These results may have implications for experiments of exciton transport in disordered organic materials. We propose that the basic phenomena can be observed in quantum simulators made of Rydberg atoms, cold molecules in optical lattices, as well as in experiments with trapped ions.

Analysis of "Cavity Enhanced Transport of Excitons"

The research paper titled "Cavity Enhanced Transport of Excitons" addresses the modulation of exciton transport properties in disordered organic materials by embedding them within an optical cavity. This work, conducted by Schachenmayer, Genes, Tignone, and Pupillo, provides theoretical insights into the phenomenon where coupling the material to a structured electromagnetic vacuum field of a Fabry-Perot cavity can significantly enhance transport efficiency.

The primary claim of the paper is that the inclusion of excitons in an optical cavity alters the transport dynamics from a tunneling-dominated process to one mediated by delocalized polariton modes. The cavity modifies the electromagnetic vacuum mode structure, facilitating transport characterized by a transition from exponential to algebraic suppression. For a one-dimensional system, this enhancement results in a shift from exponential transmission decay, typical of disordered systems, to a decay proportional to $N^{-2}$, where $N$ denotes system size.

Key numerical results are provided through simulations of wavepacket propagation and steady-state exciton currents under incoherent pumping. In a wavepacket scattering experiment involving a chain of two-level systems within a cavity, the paper demonstrates ultra-fast transmission achievable due to polariton mode coupling. The transmission in systems extends beyond distances characterized by Anderson localization when a strong collective coupling, $g\sqrt{N}$, exceeds other energy scales such as the cavity decay rate $\kappa$.

Remarkably, the paper indicates a profound enhancement of exciton transport even with weak coupling conditions. The phenomenon whereby small values of cavity coupling $g$ could maintain non-zero exciton transmission is counterintuitive given typical disorder dynamics in organic semiconductors. The research illustrates that in scenarios where $g$ is much smaller compared to $J$ (nearest-neighbor tunneling), numerically the outcomes still exhibit an increase in transport phenomena albeit with reduced quantum efficiencies.

From an experimental perspective, the work suggests that realistic setups, such as molecular semiconductors coupled to cavities, quantum simulators built with Rydberg atoms, polar molecular systems, and ions in optical lattices, can demonstrate these enhancements, supporting scalability even to systems involving up to 10,000 sites. The paper explicitly specifies conditions under which transport improvement is noticeable, such as a robust exciton-cavity coupling regime and the mitigation of disorder-induced localization effects.

The implications of these findings extend to enhancing conductivity in organic materials, challenging traditional semiconductor design paradigms. If the findings can be experimentally corroborated, practical applications in energy transfer, such as in photovoltaic devices, could see cost and efficiency improvements, offering a valuable alternative to silicon-based technologies.

Future developments in this domain could involve experimental verification of the theoretical predictions and exploring coherent transport of correlations beyond energy propagation. The paper opens avenues for advancing quantum information transport research and optimizing exciton-transport in organic electronic devices.

Overall, the investigation into exciton-cavity coupling provides compelling theoretical evidence for enhanced transport properties, projecting exciting potential practical applications in materials science and quantum technologies.