Investigation of Origin of High-Temperature Superfluorescence in Lead-Halide Perovskites

Investigation of the Role of Quantum Analog of Vibrational Isolation in Room Temperature Macroscopic Quantum Phenomena Kenan Gundogdu, NC State University

This proposal aims to find the material properties that lead to macroscopic quantum phase transition at the highest possible temperatures. Macroscopic quantum states form when an ensemble of quantum oscillators reaches a collectively coherent state. Quantum coherence, i.e., the phase stability of a quantum oscillator, is the most fundamental requirement for macroscopic coherence. In solids, thermal lattice motion (phonons) destroys the quantum phase. Therefore, macroscopically coherent quantum states require suppressing phonon populations by cooling materials to cryogenic temperatures. This program aims to find ways to suppress phonon scattering with electronic excitations in solid-state systems, to enable observation of exotic macroscopic quantum phenomena at unprecedentedly high temperatures.

We will experimentally study high-temperature superfluorescence in lead-halide perovskites to reach this goal. In superfluorescence, an ensemble of optically excited electron-hole pairs forms dipoles that oscillate with a frequency corresponding to the material's band gap. Through nonlinear interactions, these dipole oscillators synchronize, reach a macroscopically coherent state, and create a giant dipole, which radiates a burst of photons. Because in a solid, typical electronic dephasing time is in order of femtoseconds at high temperatures, superfluorescence generally forms at cryogenic conditions. Therefore, observation of high-temperature superfluorescence in lead-halide perovskites indicates a mechanism that protects quantum coherence in these materials. We postulate that large polarons in this system provide a Quantum Analog of Vibrational Isolation or QAVI and protect the electronic excitations from thermal noise. This program will explore QAVI using ultrafast spectroscopy to study superfluorescence in lead-halide perovskites.

These studies will reveal a new fundamental understanding of quantum coherence and change how we think about macroscopic quantum phase transitions. Through the investigation of QAVI, we will pave the way for designer quantum materials and accelerate the discovery of other macroscopic quantum phenomena at high temperatures.