Title: Amplitude- and Phase-Resolved Nanospectral Imaging of Phonon Polaritons in Hexagonal Boron Nitride

Abstract

Phonon polaritons are quasiparticles resulting from strong coupling of photons with optical phonons. Excitation and control of these quasiparticles in 2D materials offer the opportunity to confine and transport light at the nanoscale. Here, we image the phonon polariton (PhP) spectral response in thin hexagonal boron nitride (hBN) crystals as a representative 2D material using amplitude- and phase-resolved scattering scanning near-field optical microscopy (s-SNOM) using broadband mid-IR synchrotron radiation. The large spectral bandwidth enables the simultaneous measurement of both out-of-plane (780 cm^-1) and in-plane (1370 cm^-1) hBN phonon modes. In contrast to the strong in-plane mode, the out-of-plane PhP mode response is weak. Measurements of the PhP wavelength reveal a proportional dependence on sample thickness for thin hBN flakes, which can be understood by a general model describing two-dimensional polariton excitation in ultrathin materials.

Authors:

Shi, Zhiwen ^[1]; Bechtel, Hans A.; Berweger, Samuel ^[2]; Sun, Yinghui ^[1]; Zeng, Bo ^[1]; Jin, Chenhao ^[1]; Chang, Henry ^[1]; Martin, Michael C.; Raschke, Markus B. ^[3]; Wang, Feng ^[4]

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+ Show Author Affiliations

1. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
2. National Institute of Standards and Technology, Boulder, Colorado 80305, United States, Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, United States
3. Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, United States
4. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States, Kavli Energy NanoSciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

Publication Date:

Mon Jun 15 00:00:00 EDT 2015

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division

OSTI Identifier:

1190648

Alternate Identifier(s):

OSTI ID: 1762160

Grant/Contract Number:  

FG02-12ER46893; AC02-05CH11231

Resource Type:

Published Article

Journal Name:

ACS Photonics

Additional Journal Information:

Journal Name: ACS Photonics Journal Volume: 2 Journal Issue: 7; Journal ID: ISSN 2330-4022

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

74 ATOMIC AND MOLECULAR PHYSICS; phonon polariton; boron nitride; near-field spectroscopy; synchrotron infrared nanospectroscopy (SINS)