Coherent feedback control of two-dimensional excitons

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Coherent feedback control of two-dimensional excitons

Christopher Rogers, Dodd Gray, Jr., Nathan Bogdanowicz, Takashi Taniguchi, Kenji Watanabe, and Hideo Mabuchi

Phys. Rev. Research 2, 012029(R) – Published 31 January 2020

Abstract

Electric dipole radiation can be controlled by engineering of the photonic environment. A coherent interaction between forward and backward emission depends interferometrically on the position of a nearby mirror. The transverse coherence of exciton emission in a single layer of ${MoSe}_{2}$ and the highly radiatively broadened nature of our samples removes fundamental physical limitations of previous experiments employing pointlike dipoles. This enables full control over the exciton radiative coupling rate and total linewidth at cryogenic temperatures from near zero to $1.8 \pm 0.4 meV$ and from 0.9 to $2.3 \pm 0.1 meV$ , respectively.

Received 19 March 2019
Revised 15 December 2019

DOI:https://doi.org/10.1103/PhysRevResearch.2.012029

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Coherent control Excitons Light-matter interaction Quantum coherence & coherence measures

Transition metal dichalcogenides

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Christopher Rogers ^1,*, Dodd Gray, Jr.¹, Nathan Bogdanowicz¹, Takashi Taniguchi², Kenji Watanabe², and Hideo Mabuchi^1,†

¹Ginzton Laboratory, Stanford University, 348 Via Pueblo, Stanford, California 94305, USA
²National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

^*cmrogers@stanford.edu
^†hmabuchi@stanford.edu

Article Text

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Issue

Vol. 2, Iss. 1 — January - March 2020

Subject Areas

Condensed Matter Physics

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Images

Figure 1
Sample characterization. (a) A schematic of the heterostructure device. The Au mirror is mounted on a mechanical actuator so that $z$ can be varied. (b) A microscope image of the sample. The monolayer ${MoSe}_{2}$ region is outlined in burgundy. A few-layer graphene flake outlined in black on the bottom of the stack electrostatically isolates the ${MoSe}_{2}$ from the ${SiO}_{2}$ substrate. The bottom hBN is outlined in blue. (c) Spatial maps of the maximum dip in reflection at $X_{0}$ , and its center wavelength ${λ らむだ}_{X_{0}}$ from a region of the sample corresponding to the area outlined with dashed white lines in panel (b). (d) Selected reflection spectra corresponding to the marked positions in panel (c). These spectra were collected at 4 K with the mirror positioned slightly away from maximum destructive interference.
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Figure 2
Experimental and modeled reflectance. (a) Measured and modeled reflectance spectra near the $X_{0}$ resonance as $z$ is varied over a full fringe. Measurements at 4 K. Note that these data come from near the region marked with a purple circle in Fig. 1. (b) A schematic representation of the effect of mirror position $z$ on the the exciton resonance. The black double-headed arrow represents the exciton electric dipole, and the blue and orange curves represent the electric field emitted toward and away from the mirror, respectively. The electric field reflected by the mirror is represented in green. To the right of the monolayer, the fields interfere either constructively or destructively depending on mirror position. The corresponding schematic plots represent the modulation of amplitude and linewidth of the $X_{0}$ feature. The $z_{d}$ and $z_{c}$ values, shown for the destructive and constructive interference cases respectively, assume a perfect mirror with zero skin depth. For simplicity, multiple reflections and the full heterostructure have been omitted. (c) Selected line cuts of the measured and modeled reflectance in the spectral region of $X_{0}$ . The black arrows indicate increasing $z$ . (d) Measured reflectance, both absolute and normalized, at two $z$ positions highlighting the modulation of total linewidth.
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Figure 3
Extracted and modeled linewidths. (a) The FWHM linewidth ${γ がんま}_{tot}$ both from the model and extracted from the experimental data. Note that we cannot extract linewidth data over the full range of the experimental data, since near $z_{d}$ the $X_{0}$ resonance is almost completely extinguished. Also shown are ${γ がんま}_{r}$ and ${γ がんま}_{n r}$ from the model. (b) Center frequency ${ω おめが}_{X_{0}}$ for both model and experiment. (c) Minimum reflectance for both model and experiment. The shading in panels (a)–(c) represents the uncertainties in the model; see Ref. [52]. (d) Simplified models of the total linewidth modulation for both a point and 2D dipole, assuming a perfect mirror with zero skin depth. The top panel shows the ideal case with coherent quantum efficiency in vacuum ${η いーた}_{0} = 1$ , and the bottom panel shows the case with ${η いーた}_{0} = 0.45$ . Both are shown alongside the experimental data.
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