The Reststrahlen Effect in the Optically Thin Limit: A Framework for Resonant Response in Thin Media

Nano Letters, vol. 22, pp. 8389–8393

Abstract

Sharp resonances can strongly modify the electromagnetic response of matter. A classic example is the Reststrahlen effect - high reflectivity in the mid-infrared in many polar crystals near their optical phonon resonances. Although this effect in bulk materials has been studied extensively, a systematic treatment for finite thickness remains challenging. Here we describe, experimentally and theoretically, the Reststrahlen response in hexagonal boron nitride across more than 5 orders of magnitude in thickness, down to a monolayer. We find that the high reflectivity plateau of the Reststrahlen band evolves into a single peak as the material enters the optically thin limit, within which two distinct regimes emerge: a strong-response regime dominated by coherent radiative decay and a weak-response regime dominated by damping. We show that this evolution can be explained by a simple two-dimensional sheet model that can be applied to a wide range of thin media.

Authors 7

1. Yue Ma corresponding

   SLAC National Accelerator Laboratory · University of California, Berkeley · Stanford University

   Affiliation as printed

   Department of Applied Physics, Stanford University, Stanford, California 94305, United States

   Department of Physics, University of California, Berkeley, Berkeley, California 94720, United States

   SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States

2. Jenny C. Hu

   SLAC National Accelerator Laboratory · Stanford University

   Affiliation as printed

   Department of Applied Physics, Stanford University, Stanford, California 94305, United States

   SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States

3. Lutz Waldecker Aachen 2nd Institute of Physics

   SLAC National Accelerator Laboratory · RWTH Aachen University · Stanford University

   Affiliation as printed

   2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany

   Department of Applied Physics, Stanford University, Stanford, California 94305, United States

   SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States

4. Kenji Watanabe

   National Institute for Materials Science

   Affiliation as printed

   Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

5. Takashi Taniguchi

   National Institute for Materials Science

   Affiliation as printed

   International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

6. Fang Liu

   Stanford University

   Affiliation as printed

   Department of Chemistry, Stanford University, Stanford, California 94305, United States

7. Tony F. Heinz corresponding

   SLAC National Accelerator Laboratory · Stanford University

   Affiliation as printed

   Department of Applied Physics, Stanford University, Stanford, California 94305, United States

   SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States