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  1. Article ; Online: Polaron-induced changes in moiré exciton propagation in twisted van der Waals heterostructures.

    Knorr, Willy / Brem, Samuel / Meneghini, Giuseppe / Malic, Ermin

    Nanoscale

    2024  

    Abstract: Twisted transition metal dichalcogenides (TMDs) present an intriguing platform for exploring excitons and their transport properties. By introducing a twist angle, a moiré superlattice forms, providing a spatially dependent exciton energy landscape. ... ...

    Abstract Twisted transition metal dichalcogenides (TMDs) present an intriguing platform for exploring excitons and their transport properties. By introducing a twist angle, a moiré superlattice forms, providing a spatially dependent exciton energy landscape. Based on a microscopic many-particle theory, we investigate in this work polaron-induced changes in exciton transport properties in the exemplary MoSe
    Language English
    Publishing date 2024-04-16
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d4nr00136b
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Excitonic Thermalization Bottleneck in Twisted TMD Heterostructures.

    Meneghini, Giuseppe / Brem, Samuel / Malic, Ermin

    Nano letters

    2024  Volume 24, Issue 15, Page(s) 4505–4511

    Abstract: Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited ... ...

    Abstract Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited states show lifetimes that are several orders of magnitude longer than in monolayers. The origin of this behavior is still under debate. Based on a microscopic many-particle approach, we investigate the phonon-driven relaxation cascade of nonequilibrium moiré excitons in the exemplary MoSe
    Language English
    Publishing date 2024-04-05
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.4c00450
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Bosonic Delocalization of Dipolar Moiré Excitons.

    Brem, Samuel / Malic, Ermin

    Nano letters

    2023  Volume 23, Issue 10, Page(s) 4627–4633

    Abstract: In superlattices of twisted semiconductor monolayers, tunable moiré potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent ... ...

    Abstract In superlattices of twisted semiconductor monolayers, tunable moiré potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent dipole providing a unique opportunity to study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties of moiré excitons, which could play a key role for technological applications. However, the intriguing interplay between exciton-exciton interactions and moiré trapping has not been well understood yet. In this work, we develop a microscopic theory of interacting excitons in external potentials allowing us to tackle this highly challenging problem. We find that interactions between moiré excitons lead to a delocalization at intermediate densities, and we show how this transition can be tuned via twist angle and temperature. The delocalization is accompanied by a modification of optical moiré resonances, which gradually merge into a single free exciton peak.
    Language English
    Publishing date 2023-05-15
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.3c01160
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Terahertz Fingerprint of Monolayer Wigner Crystals.

    Brem, Samuel / Malic, Ermin

    Nano letters

    2022  Volume 22, Issue 3, Page(s) 1311–1315

    Abstract: The strong Coulomb interaction in monolayer semiconductors represents a unique opportunity for the realization of Wigner crystals without external magnetic fields. In this work, we predict that the formation of monolayer Wigner crystals can be detected ... ...

    Abstract The strong Coulomb interaction in monolayer semiconductors represents a unique opportunity for the realization of Wigner crystals without external magnetic fields. In this work, we predict that the formation of monolayer Wigner crystals can be detected by their terahertz response spectrum, which exhibits a characteristic sequence of internal optical transitions. We apply the density matrix formalism to derive the internal quantum structure and the optical conductivity of the Wigner crystal and to microscopically analyze the multipeak shape of the obtained terahertz spectrum. Moreover, we predict a characteristic shift of the peak position as a function of charge density for different atomically thin materials and show how our results can be generalized to an arbitrary two-dimensional system.
    Language English
    Publishing date 2022-01-20
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.1c04620
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Trion Photoluminescence and Trion Stability in Atomically Thin Semiconductors.

    Perea-Causin, Raul / Brem, Samuel / Schmidt, Ole / Malic, Ermin

    Physical review letters

    2024  Volume 132, Issue 3, Page(s) 36903

    Abstract: The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model ... ...

    Abstract The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model consistently capturing bright and dark trion peaks is still lacking. In this work, we derive a generalized trion PL formula on a quantum-mechanical footing, considering direct and phonon-assisted recombination mechanisms. We show the trion energy landscape in WSe_{2} by solving the trion Schrödinger equation. We reveal that the mass imbalance between equal charges results in less stable trions exhibiting a small binding energy and, interestingly, a large energetic offset from exciton peaks in PL spectra. Furthermore, we compute the temperature-dependent PL spectra for n- and p-doped monolayers and predict yet unobserved signatures originating from trions with an electron at the Λ point. Our work presents an important step toward a microscopic understanding of the internal structure of trions determining their stability and optical fingerprint.
    Language English
    Publishing date 2024-01-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.132.036903
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Book ; Online: Bosonic Delocalization of Dipolar Moir\'e Excitons

    Brem, Samuel / Malic, Ermin

    2023  

    Abstract: In superlattices of twisted semiconductor monolayers, tunable moir\'e potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent ...

    Abstract In superlattices of twisted semiconductor monolayers, tunable moir\'e potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent dipole providing a unique opportunity to study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties of moir\'e excitons, which could play a key role for technological applications. However, the intriguing interplay between exciton-exciton interactions and moir\'e trapping has not been well understood yet. In this work, we develop a microscopic theory of interacting excitons in external potentials allowing us to tackle this highly challenging problem. We find that interactions between moir\'e excitons lead to a delocalization at intermediate densities and we show how this transition can be tuned via twist angle and temperature. The delocalization is accompanied by a modification of optical moir\'e resonances, which gradually merge into a single free exciton peak. The predicted density-tunability of the supercell hopping can be utilized to control the energy transport in moir\'e materials.
    Keywords Condensed Matter - Mesoscale and Nanoscale Physics ; Condensed Matter - Materials Science ; Physics - Computational Physics ; Quantum Physics
    Subject code 530
    Publishing date 2023-06-01
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Exciton transport in atomically thin semiconductors.

    Malic, Ermin / Perea-Causin, Raül / Rosati, Roberto / Erkensten, Daniel / Brem, Samuel

    Nature communications

    2023  Volume 14, Issue 1, Page(s) 3430

    Language English
    Publishing date 2023-06-10
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-023-38556-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Phonon-assisted exciton dissociation in transition metal dichalcogenides.

    Perea-Causín, Raül / Brem, Samuel / Malic, Ermin

    Nanoscale

    2021  Volume 13, Issue 3, Page(s) 1884–1892

    Abstract: Monolayers of transition metal dichalcogenides (TMDs) have been established in the last years as promising materials for novel optoelectronic devices. However, the performance of such devices is often limited by the dissociation of tightly bound excitons ...

    Abstract Monolayers of transition metal dichalcogenides (TMDs) have been established in the last years as promising materials for novel optoelectronic devices. However, the performance of such devices is often limited by the dissociation of tightly bound excitons into free electrons and holes. While previous studies have investigated tunneling at large electric fields, we focus in this work on phonon-assisted exciton dissociation that is expected to be the dominant mechanism at small fields. We present a microscopic model based on the density matrix formalism providing access to time- and momentum-resolved exciton dynamics including phonon-assisted dissociation. We track the pathway of excitons from optical excitation via thermalization to dissociation, identifying the main transitions and dissociation channels. Furthermore, we find intrinsic limits for the quantum efficiency and response time of a TMD-based photodetector and investigate their tunability with externally accessible knobs, such as excitation energy, substrate screening, temperature and strain. Our work provides microscopic insights in fundamental mechanisms behind exciton dissociation and can serve as a guide for the optimization of TMD-based optoelectronic devices.
    Language English
    Publishing date 2021-01-13
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d0nr07131e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Electrically tunable dipolar interactions between layer-hybridized excitons.

    Erkensten, Daniel / Brem, Samuel / Perea-Causín, Raül / Hagel, Joakim / Tagarelli, Fedele / Lopriore, Edoardo / Kis, Andras / Malic, Ermin

    Nanoscale

    2023  Volume 15, Issue 26, Page(s) 11064–11071

    Abstract: Transition-metal dichalcogenide bilayers exhibit a rich exciton landscape including layer-hybridized excitons, ...

    Abstract Transition-metal dichalcogenide bilayers exhibit a rich exciton landscape including layer-hybridized excitons,
    Language English
    Publishing date 2023-07-06
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d3nr01049j
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Exciton transport in atomically thin semiconductors

    Ermin Malic / Raül Perea-Causin / Roberto Rosati / Daniel Erkensten / Samuel Brem

    Nature Communications, Vol 14, Iss 1, Pp 1-

    2023  Volume 4

    Abstract: Atomically thin semiconductors have been in the center of one of the most active research fields. Here, we discuss the main challenges in exciton transport that is crucial for nanoelectronics. We focus on transport phenomena in monolayers, lateral ... ...

    Abstract Atomically thin semiconductors have been in the center of one of the most active research fields. Here, we discuss the main challenges in exciton transport that is crucial for nanoelectronics. We focus on transport phenomena in monolayers, lateral heterostructures, and twisted heterostacks of transition metal dichalcogenides.
    Keywords Science ; Q
    Language English
    Publishing date 2023-06-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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