Measuring Valley Polarization in Two-Dimensional Materials with Second-Harmonic Spectroscopy

• Type: Article in International Scientific Journal
• Date: 2020

Authors

Ho, YW (Author) Other; Rosa, HG (Author) Other; Verzhbitskiy, I (Author) Other; Rodrigues, MJLF (Author) Other; Taniguchi, T (Author) Other; Watanabe, K (Author) Other; Eda, G (Author) Other; Pereira, VM (Author) Other; Viana Gomes, JC (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: ACS Photonics

Vol. 7

Pages: 925-931

ISSN: 2330-4022

Indexing

ISI Web of Knowledge - 19 Citations

Scopus - 21 Citations

Scientific classification

CORDIS: Physical sciences > Physics > Solid state physics

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-00S-3G6

DOI: 10.1021/acsphotonics.0c00174

Abstract (EN): A population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such imbalance (a valley polarization), which exploits the unique fingerprints of this symmetry reduction in the polarization-dependent second-harmonic generation (SHG). We present the principle and detection scheme in the context of hexagonal two-dimensional crystals, which include graphene-based systems and the family of transition metal dichalcogenides, and provide a direct experimental demonstration using a molybdenum diselenide monolayer with 2H polytype at room temperature. We deliberately use the simplest possible setup, where a single pulsed laser beam simultaneously controls the valley imbalance and tracks the SHG process. We further developed a model of the transient population dynamics, which analytically describes the valley-induced SHG rotation in very good agreement with the experimental data. In addition to providing the first experimental demonstration of the effect, this work establishes a conceptually simple, compact, and transferable way of measuring instantaneous valley polarization, with direct applicability in the nascent field of valleytronics. © 2020 American Chemical Society.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7