Emergence of Macroscopic Quantum Order via Translational Zero Modes

Abstract

Macroscopic quantum coherence in solids, such as in superfluids, superconductors, and condensates, is generally limited to low temperatures because order forms within a fixed excitation spectrum whose competing states become thermally populated as temperature rises. Here, we show that strong coupling between electronic excitations and a deformable lattice enables a different route. Above a critical density, this coupling nucleates self generated confining potentials that trap the very excitations generating them. Unlike rigid external traps, these potentials can translate through the host lattice without changing their internal structure, defining a translational zero mode. Coupling to this zero mode provides a shared dynamical coordinate that lowers and isolates a single collective many body configuration, opening a density dependent gap that suppresses thermal occupation of competing states and supports off diagonal long range order at elevated temperatures. As a concrete realization, we identify high-temperature superfluorescence in lead halide perovskites as the radiative instability of this zero mode dressed ordered excitonic state. More broadly, this establishes a general route to macroscopic quantum order: not cooling within a fixed spectrum, nor pairing instabilities, but a self generated mobile confining structure whose translational zero mode reconstructs the many-body spectrum to protect coherence.