Topological nanophononic states by band inversion

Abstract

Nanophononics is essential for the engineering of thermal transport in nanostructured electronic devices, it greatly facilitates the manipulation of mechanical resonators in the quantum regime, and could unveil a new route in quantum communications using phonons as carriers of information. Acoustic phonons also constitute a versatile platform for the study of fundamental wave dynamics, including Bloch oscillations, Wannier Stark ladders and other localization phenomena. Many of the phenomena studied in nanophononics were indeed inspired by their counterparts in optics and electronics. In these fields, the consideration of topological invariants to control wave dynamics has already had a great impact for the generation of robust confined states. Interestingly, the use of topological phases to engineer nanophononic devices remains an unexplored and promising field. Conversely, the use of acoustic phonons could constitute a rich platform to study topological states. Here, we introduce the concept of topological invariants to nanophononics and experimentally implement a nanophononic system supporting a robust topological interface state at 350 GHz. The state is constructed through band inversion, i.e. by concatenating two semiconductor superlattices with inverted spatial mode symmetries. The existence of this state is purely determined by the Zak phases of the constituent superlattices, i.e. that one-dimensional Berry phase. We experimentally evidenced the mode through Raman spectroscopy. The reported robust topological interface states could become part of nanophononic devices requiring resonant structures such as sensors or phonon lasers.

21 pages, 7 figures

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• Topological Thermoelectricity in Metals
• Topological acoustics in coupled nanocavity arrays
• Microcavity phonoritons -- a coherent optical-to-microwave interface
• Topology of Triple-Point Metals
• Coherent generation and detection of acoustic phonons in topological nanocavities
• Brillouin Scattering in Hybrid Optophononic Bragg Micropillar Resonators at 300 GHz
• Experimental realization of topological on-chip acoustic tweezers
• Fiber-integrated microcavities for efficient generation of coherent acoustic phonons
• Phonon engineering with superlattices: generalized nanomechanical potentials
• Fragile phonon topology on the honeycomb lattice with time-reversal symmetry
• Topological interface states induced by incident angle in the 1D elastic wave system
• Topological phonon analysis of the 2D buckled honeycomb lattice: an application to real materials
• Fiber-based angular filtering for high-resolution Brillouin spectroscopy in the 20-300 GHz frequency range
• Coherent phonon lasing in a thermal quantum nanomachine
• Long-Lived Coherent Acoustic Phonons in Epitaxially Grown III-V Adiabatic Cavities
• Topological optical and phononic interface mode by simultaneous band inversion