Anatolie Mitioglu

Radboud University Nijmegen

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Paulina Płochocka

Centre National de la Recherche Scientifique

Peter C. M. Christianen

Radboud University Nijmegen

L. Kulyuk

Institute of Applied Physics

Mariana V. Ballottin

Radboud University Nijmegen

S. Anghel

TU Dortmund University

Alessandro Surrente

Wrocław University of Science and Technology

Krzysztof Gałkowski

University of Cambridge

D. K. Maude

Centre National de la Recherche Scientifique

Alexey Chernikov

TU Dresden

Tobias Korn

National Institute for Materials Science

Cooperative Institutions

Centre National de la Recherche Scientifique

Université Grenoble Alpes

Laboratoire National des Champs Magnétiques Intenses

Université Toulouse III - Paul Sabatier

University of Cambridge

Institut National des Sciences Appliquées de Toulouse

Université Joseph Fourier

Russian Academy of Sciences

Ioffe Institute

Sorbonne Université

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Valley-magnetophonon resonance for interlayer excitons

2D Materials (2022)

D. S. Smirnov Johannes Höller Michael Kempf Jonas Zipfel Philipp Nagler

Abstract Heterobilayers consisting of MoSe 2 and WSe 2 monolayers can host optically bright interlayer excitons with intriguing properties such as ultralong lifetimes and pronounced circular polarization of their photoluminescence due to valley polarization, which can be induced by circularly polarized excitation or applied magnetic fields. Here, we report on the observation of an intrinsic valley-magnetophonon resonance for localized interlayer excitons promoted by invervalley hole scattering. It leads to a resonant increase of the photoluminescence polarization degree at the same field of 24.2 Tesla for H-type and R-type stacking configurations despite their vastly different excitonic energy splittings. As a microscopic mechanism of the hole intervalley scattering we identify the scattering with chiral TA phonons of MoSe 2 between excitonic states mixed by the long-range electron hole exchange interaction.

10.1088/2053-1583/ac8602

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Citations (7)

Intervalley scattering of excitons and trions in monolayer WSe$_{2}$ under strong excitation

arXiv (Cornell University) (2015)

Anatolie Mitioglu Ł. Kłopotowski D. K. Maude G. Deligeorgis S. Anghel

Monolayer transition metal dichalcogenides offer the possibility of optical control of the valley degree of freedom. In order to asses the potential of these materials in applications, detailed knowledge of the valley dynamics is essential. In this work, we apply low temperature time-resolved photoluminescence (PL) measurements to investigate exciton valley relaxation dynamics and, in particular, its behavior under strong excitation. At the lowest excitation powers the inter valley scattering time is $\simeq 50$ ps, but shortens by more than a factor of two at the highest powers. We attribute this acceleration to either heating of the exciton system or the presence of a dense exciton gas, which could influence the exciton valley properties. Furthermore, we analyze the PL dynamics of excitons and trions. We find that the PL decays for all peaks are bi-exponential and approximately independent of the excitation power. We attribute the short decay to radiative recombination and escape to a reservoir of dark states. The long decay is ascribed to a transfer of excitons back from the reservoir. For the first time, we evaluate the exciton PL decay time of $\simeq$ 10 ps. The latter process is valley-conserving and occurs on a timescale of $\simeq$ 50 ps.

Exponential decay

10.48550/arxiv.1507.00496

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Citations (1)

Addressing the exciton fine structure in colloidal nanocrystals: the case of CdSe nanoplatelets

Nanoscale (2017)

Elena V. Shornikova Louis Biadala D. R. Yakovlev V. F. Sapega Yuri G. Kusrayev

We study the band-edge exciton fine structure and in particular its bright-dark splitting in colloidal semiconductor nanocrystals by four different optical methods based on fluorescence line narrowing and time-resolved measurements at various temperatures down to 2 K. We demonstrate that all these methods provide consistent splitting values and discuss their advances and limitations. Colloidal CdSe nanoplatelets with thicknesses of 3, 4 and 5 monolayers are chosen for experimental demonstrations. The bright-dark splitting of excitons varies from 3.2 to 6.0 meV and is inversely proportional to the nanoplatelet thickness. Good agreement between experimental and theoretically calculated size dependence of the bright-dark exciton slitting is achieved. The recombination rates of the bright and dark excitons and the bright to dark relaxation rate are measured by time-resolved techniques.

Fine structure

10.1039/c7nr07206f

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Citations (90)

Site-selective measurement of coupled spin pairs in an organic semiconductor

Proceedings of the National Academy of Sciences (2018)

Sam L. Bayliss Leah R. Weiss Anatolie Mitioglu Krzysztof Gałkowski Zhuo Yang

Significance Pairs of spins in molecular materials have attracted significant interest as intermediates in photovoltaic devices and light-emitting diodes. However, isolating the local spin and electronic environments of such intermediates has proved challenging due to the complex structures in which they reside. Here we show how exchange coupling can be used to select and characterize multiple coexisting pairs, enabling joint measurement of their exchange interactions and optical profiles. We apply this to spin-1 pairs formed by photon absorption whose coupling gives rise to total-spin S = 0,1 and 2-pair configurations with drastically different properties. This presents a way of identifying the molecular conformations involved in spin-pair processes and generating design rules for more effective use of interacting spins.

Organic semiconductor

10.1073/pnas.1718868115

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Citations (52)

Negatively Charged and Dark Excitons in CsPbBr₃ Perovskite Nanocrystals Revealed by High Magnetic Fields

Nano Letters (2017)

Damien Canneson Elena V. Shornikova D. R. Yakovlev Tobias Rogge Anatolie Mitioglu

The optical properties of colloidal cesium lead halide perovskite (CsPbBr3) nanocrystals are examined by time-resolved and polarization-resolved spectroscopy in high magnetic fields up to 30 T. We unambiguously show that at cryogenic temperatures the emission is dominated by recombination of negatively charged excitons with radiative decay time of 300 ps. The additional long-lived emission, which decay time shortens from 40 down to 8 ns and in which the decay time shortens and relative amplitude increases in high magnetic fields, evidences the presence of a dark exciton. We evaluate g-factors of the bright exciton gX = +2.4, the electron ge = +2.18, and the hole gh = -0.22.

10.1021/acs.nanolett.7b02827

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Citations (115)

Direct measurement of the exciton binding energy and effective masses for charge carriers in organic–inorganic tri-halide perovskites

Nature Physics (2015)

Atsuhiko Miyata Anatolie Mitioglu Paulina Płochocka O. Portugall Jacob Tse‐Wei Wang

Charge carrier

10.1038/nphys3357

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Citations (1,839)

Anomalous rotation of the linearly polarized emission of bright excitons in strained WSe2 monolayers under high magnetic fields

Physical review. B./Physical review. B (2019)

Anatolie Mitioglu S. Anghel Mariana V. Ballottin K. Sushkevich L. Kulyuk

Linearly polarized microphotoluminescence ($\ensuremath{\mu}$-PL) measurements of strained ${\mathrm{WSe}}_{2}$ monolayers in out-of-plane high magnetic fields are presented. At low temperature, a splitting of the bright exciton emission into two exciton components is observed, which is attributed to an in-plane uniaxial strain based on the full polarization dependence of the photoluminescence spectrum. High magnetic field measurements directly reveal a distinct evolution of the linear polarization and allows us to extract the valley coherence time constants (${T}_{s2}^{*}$) for both exciton components. For the high-energy transition of the exciton, the valley coherence time $\ensuremath{\simeq}0.45$ ps, closely matching ${T}_{s2}^{*}$ of an unstrained monolayer ($\ensuremath{\simeq}0.34$ ps). For the low-energy exciton, however, ${T}_{s2}^{*}$ is four times larger, $\ensuremath{\simeq}1.97$ ps. This valley coherence time observed here may be explored for future valleytronic applications.

10.1103/physrevb.99.155414

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Citations (5)

Magneto-transport properties of a random distribution of few-layer graphene patches

Journal of Applied Physics (2014)

Fabrice Iacovella Pierre Trinsoutrot Anatolie Mitioglu Véronique Conédéra M. Pierre

In this study, we address the electronic properties of conducting films constituted of an array of randomly distributed few layer graphene patches and investigate on their most salient galvanometric features in the moderate and extreme disordered limit. We demonstrate that, in annealed devices, the ambipolar behaviour and the onset of Landau level quantization in high magnetic field constitute robust hallmarks of few-layer graphene films. In the strong disorder limit, however, the magneto-transport properties are best described by a variable-range hopping behaviour. A large negative magneto-conductance is observed at the charge neutrality point, in consistency with localized transport regime.

Ambipolar diffusion

Landau quantization

Magneto

Variable-range hopping

10.1063/1.4901953

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Citations (2)

Edge effects in second-harmonic generation in nanoscale layers of transition-metal dichalcogenides

Semiconductors (2015)

Е. Д. Мишина N. É. Sherstyuk A. P. Shestakova S. D. Lavrov Sergey Semin

Crystal (programming language)

Harmonic

Band bending

10.1134/s1063782615060159

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Citations (9)

Giant magnetic splitting inducing near-unity valley polarization in van der Waals heterostructures

Nature Communications (2017)

Philipp Nagler Mariana V. Ballottin Anatolie Mitioglu Fabian Mooshammer Nicola Paradiso

Monolayers of semiconducting transition metal dichalcogenides exhibit intriguing fundamental physics of strongly coupled spin and valley degrees of freedom for charge carriers. While the possibility of exploiting these properties for information processing stimulated concerted research activities towards the concept of valleytronics , maintaining control over spin-valley polarization proved challenging in individual monolayers. A promising alternative route explores type II band alignment in artificial van der Waals heterostructures. The resulting formation of interlayer excitons combines the advantages of long carrier lifetimes and spin-valley locking . Here, we demonstrate direct magnetic manipulation of valley polarization in a WSe2/MoSe2 heterostructure through giant valley Zeeman splitting of interlayer transitions. Remarkably, even after non-selective injection, the observed $g$ factor as large as $-15$ induces near-unity polarization of long-lived excitons with 100 ns lifetimes under magnetic fields. The demonstrated control of the spin-valley physics highlights the exceptional aspects of novel, artificially designed material systems and their promise for atomically-thin valleytronic devices.

Valleytronics

10.1038/s41467-017-01748-1

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Citations (139)