Tailoring phonon coherence through vibrational strong coupling for ballistic electron flow in semiconductors
Abstract
Approved for Public ReleaseElectronic transport underpins the function of all semiconductor technologies. At temperatures greater than a few Kelvin, transport is severely limited by scattering between electrons and lattice vibrations (phonons). Scattering is the most important energy loss channel, translating to operating speeds and power efficiencies that fall far below theoretical maxima for technologies ranging from microprocessors to photovoltaics. Breaking through these limits requires semiconductors that sustain long-range ballistic (scatter-free) electronic transport. Here, we propose a new approach to achieve ballistic electronic energy flow at room temperature by suppressing short-range electron-phonon interactions. We will achieve this suppression by leveraging strong light-matter interactions; specifically, we will embed semiconductors in photonic cavities resonant with the phonon modes that contribute most to electron-phonon interactions. The resulting strong interaction between light and phonons, known as vibrational strong coupling (VSC), leads to long-range phonon delocalization. We hypothesize that this phonon delocalization will shield electronic particles from short-range scattering. Indeed, in a recent breakthrough, we have shown that delocalized phonons can aid rather than suppress ballistic transport, even in systems with weak electronic coupling. Although such phonon-assisted ballistic transport is naturally present in a few materials, the key innovation of this proposal is to generalize this behavior by engineering phonon coherence inessentially any material through VSC. Using cutting-edge, non-contact ultrafast optical microscopy measurements with extreme spatiotemporal resolution that we pioneered, we will systematically study the effect of VSC on electron-phonon interactions and electronictransport in materials of high current interest for microelectronics and quantum transduction. Specifically, we will explore the effect of VSC on: (i) Small polaron formation and transport in self-assembled molecular semiconductors, such as J-aggregate nanotubes of cyanine chromophores; and (ii) Electron-phonon scattering and electronic decoherence in two-dimensional superatomic semiconductors, such as CsReSeI and graphullerene. The goal is to achieve sustained ballistic electronic energy flow with micrometer-scale mean free paths at room temperature, of major importance for ultra-efficient processors and wave-based quantum electronics. In addition tothe fundamental importance of studying how altered light-matter environments affect electronic materials, this work is synergistic with DoD priorities associated with photonic and phononic devices for high performance computing, quantum information processing andfunctional devices, with a focus on nano-engineered materials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512079
Entities
People
- Milan Delor
Organizations
- Office of Naval Research
- Trustees of Columbia University in the City of New York
- United States Navy