Maciej Koperski

@article{ISI:001360396900001,
title = {Nb impurity-bound excitons as quantum emitters in monolayer WS_{2}},
author = {Leyi Loh and Yi Wei Ho and Fengyuan Xuan and Andres Granados del Aguila and Yuan Chen and See Yoong Wong and Jingda Zhang and Zhe Wang and Kenji Watanabe and Takashi Taniguchi and Paul J Pigram and Michel Bosman and Su Ying Quek and Maciej Koperski and Goki Eda},
doi = {10.1038/s41467-024-54360-5},
times_cited = {0},
year = {2024},
date = {2024-11-20},
journal = {NATURE COMMUNICATIONS},
volume = {15},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Point defects in crystalline solids behave as optically addressable individual quantum systems when present in sufficiently low concentrations. In two-dimensional (2D) semiconductors, such quantum defects hold potential as versatile single photon sources. Here, we report the synthesis and optical properties of Nb-doped monolayer WS2 in the dilute limit where the average spacing between individual dopants exceeds the optical diffraction limit, allowing the emission spectrum to be studied at the single-dopant level. We show that these individual dopants exhibit common features of quantum emitters, including narrow emission lines (with linewidths <1 meV), strong spatial confinement, and photon antibunching. These emitters consistently occur within a narrow spectral range across multiple samples, distinct from common quantum emitters in van der Waals (vdW) materials that show large ensemble broadening. Analysis of the Zeeman splitting reveals that they can be attributed to bound exciton complexes comprising dark excitons and negatively charged Nb.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001010099700001,
title = {Dielectric Environment Sensitivity of Carbon Centers in Hexagonal Boron Nitride},
author = {Danis I Badrtdinov and Carlos Rodriguez-Fernandez and Magdalena Grzeszczyk and Zhizhan Qiu and Kristina Vaklinova and Pengru Huang and Alexander Hampel and Kenji Watanabe and Takashi Taniguchi and Lu Jiong and Marek Potemski and Cyrus E Dreyer and Maciej Koperski and Malte Rosner},
doi = {10.1002/smll.202300144},
times_cited = {8},
issn = {1613-6810},
year = {2023},
date = {2023-06-17},
journal = {SMALL},
volume = {19},
number = {41},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {A key advantage of utilizing van-der-Waals (vdW) materials as defect-hosting platforms for quantum applications is the controllable proximity of the defect to the surface or the substrate allowing for improved light extraction, enhanced coupling with photonic elements, or more sensitive metrology. However, this aspect results in a significant challenge for defect identification and characterization, as the defect's properties depend on the the atomic environment. This study explores how the environment can influence the properties of carbon impurity centers in hexagonal boron nitride (hBN). It compares the optical and electronic properties of such defects between bulk-like and few-layer films, showing alteration of the zero-phonon line energies and their phonon sidebands, and enhancements of inhomogeneous broadenings. To disentangle the mechanisms responsible for these changes, including the atomic structure, electronic wavefunctions, and dielectric screening, it combines ab initio calculations with a quantum-embedding approach. By studying various carbon-based defects embedded in monolayer and bulk hBN, it demonstrates that the dominant effect of the change in the environment is the screening of density-density Coulomb interactions between the defect orbitals. The comparative analysis of experimental and theoretical findings paves the way for improved identification of defects in low-dimensional materials and the development of atomic scale sensors for dielectric environments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000799109400015,
title = {Degradation Chemistry and Kinetic Stabilization of Magnetic CrI_{3}},
author = {Taiming Zhang and Magdalena Grzeszczyk and Jing Li and Wei Yu and Haomin Xu and Peng He and Liming Yang and Zhizhan Qiu and HuiHui Lin and Huimin Yang and Jian Zeng and Tao Sun and Zejun Li and Jishan Wu and Ming Lin and Kian Ping Loh and Chenliang Su and Kostya S Novoselov and Alexandra Carvalho and Maciej Koperski and Jiong Lu},
doi = {10.1021/jacs.1c08906},
times_cited = {20},
issn = {0002-7863},
year = {2022},
date = {2022-03-30},
journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
volume = {144},
number = {12},
pages = {5295-5303},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {The discovery of the intrinsic magnetic order in single-layer chromium trihalides (CrX3, X = I, Br, and Cl) has drawn intensive interest due to their potential application in spintronic devices. However, the notorious environmental instability of this class of materials under ambient conditions renders their device fabrication and practical application extremely challenging. Her; we performed a systematic investigation of the degradation chemistry of chromium iodide (CrI3), the most studied among CrX3 families, via a joint spectroscopic and microscopic analysis of the structural and composition evolution of bulk and exfoliated nanoflakes in different environments. Unlike other air-sensitive 2D materials, CrI3 undergoes a pseudo-first-order hydrolysis in the presence of pure water toward the formation of amorphous Cr(OH)(3) and hydrogen iodide (HI) with a rate constant of k(1) = 0.63 day(-1) without light. In contrast, a faster pseudo-first-order surface oxidation of CrI3 occurs in a pure O-2 environment, generating CrO3 and I-2 with a large rate constant of k(Cr) = 4.2 day(-1). Both hydrolysis and surface oxidation of CrI3 can be accelerated via light irradiation, resulting in its ultrafast degradation in air. The new chemical insights obtained allow for the design of an effective stabilization strategy for CrI3 with preserved optical and magnetic properties. The use of organic acid solvents (e.g., formic acid) as reversible capping agents ensures that CrI3 nanoflakes remain stable beyond 1 month due to the effective suppression of both hydrolysis and oxidation of CrI3.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000664289800061,
title = {Electrically Controlled Thermal Radiation from Reduced Graphene Oxide Membranes},
author = {Zhaolong Chen and Kou Yang and Tongfeng Xian and Coskun Kocabas and Sergei Morozov and Antonio Castro H Neto and Kostya S Novoselov and Daria Andreeva and Maciej Koperski},
doi = {10.1021/acsami.1c04352},
times_cited = {15},
issn = {1944-8244},
year = {2021},
date = {2021-06-04},
journal = {ACS APPLIED MATERIALS & INTERFACES},
volume = {13},
number = {23},
pages = {27278-27283},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {We demonstrate a fabrication procedure of hybrid devices that consist of reduced graphene oxide films supported by porous polymer membranes that host ionic solutions. We find that we can control the thermal radiation from the surface of reduced graphene oxide through a process of electrically driven reversible ionic intercalation. Through a comparative analysis of the structural, chemical, and optical properties of our reduced graphene oxide films, we identify that the dominant mechanism leading to the intercalation-induced reduction of light emission is Pauli blocking of the interband recombination of charge carriers. We inspect the capabilities of our devices to act as a platform for the electrical control of mid-infrared photonics by observing a bias-induced reduction of apparent temperature of hot surfaces visualized through an infrared thermal camera.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}