Ultra-flat and long-lived plasmons in a strongly correlated oxide

Abstract

Plasmons in strongly correlated systems are attracting considerable attention due to their unconventional behavior caused by electronic correlation effects. Recently, flat plasmons with nearly dispersionless frequency-wave vector relations have drawn significant interest because of their intriguing physical origin and promising applications. However, these flat plasmons exist primarily in low-dimensional materials with limited wave vector magnitudes (q < similar to 0.7 angstrom(-1)). Here, we show that long-lived flat plasmons can propagate up to similar to 1.2 angstrom(-1) in alpha-Ti2O3 , a strongly correlated three-dimensional Mottinsulator, with an ultra-small energy fluctuation (<40 meV). The strong correlation effect renormalizes the electronic bands near Fermi level with a small bandwidth, which is responsible for the flat plasmons in alpha-Ti2O3. Moreover, these flat plasmons are not affected by Landau damping over a wide range of wave vectors (q < similar to 1.2 angstrom(-1)) due to symmetry constrains on the electron wavefunctions. Our work provides a strategy for exploring flat plasmons in strongly correlated systems, which in turn may give rise to novel plasmonic devices in which flat and long-lived plasmons are desirable.