Landau Polarons as Generators of Quantum-Coherent States

TL;DR

This study demonstrates that Landau polarons in perovskite quantum dots can dynamically generate quantum-coherent states, leading to collective quantum phenomena observable at room temperature.

Contribution

It provides the first real-time observation of polaron-induced coherent state formation and introduces a Hamiltonian model explaining their size-dependent dynamics.

Findings

Delayed condensation into coherent states within 50-150 fs

Robust size-dependent spectral splittings at 300 K

Polaron dynamics enable collective quantum effects like superradiance

Abstract

Since Landau's theory, polarons have been understood as quasiparticles in which charges are dressed by the lattice field, yet decades of transport and spectroscopic studies have yielded only static indirect renormalizations. Whether such dressing can dynamically reorganize electronic spectra to generate new quantum-coherent states has remained unresolved. Here we use femtosecond coherent multidimensional spectroscopy on size and composition controlled perovskite quantum dots to track polaronic field-induced dynamics in real time, revealing their consequences. We observe a delayed condensation into a confined spectrum of coherent states on 50-150 fs timescales, with couplings between these states evolving dynamically on the same timescale. The splittings are robust, exhibit anomalous linear size dependence, exceed single-particle splittings and manifest at 300 K. A Raman-constrained spin-boson Hamiltonian captures both the anomalous scaling and dynamical onset, establishing polarons as generators of coherent manifolds that enable collective quantum phenomena including superradiance, superfluorescence and superabsorption.