Tomasz Smolenski

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Smolenski

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Tomasz

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0000-0002-4706-7777

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Publications 1 - 10 of 13

Optical Signatures of Periodic Charge Distribution in a Mott-like Correlated Insulator State
Shimazaki, Yuya; Kuhlenkamp, Clemens; Schwartz, Ido; et al. (2021)
Physical Review X
The elementary optical excitations in two-dimensional semiconductors hosting itinerant electrons are attractive and repulsive polarons—excitons that are dynamically screened by electrons. Exciton polarons have hitherto been studied in translationally invariant degenerate Fermi systems. Here, we show that periodic distribution of electrons breaks the excitonic translational invariance and leads to a direct optical signature in the exciton-polaron spectrum. Specifically, we demonstrate that new optical resonances appear due to spatially modulated interactions between excitons and electrons in an incompressible Mott-like correlated state. Our observations demonstrate that resonant optical spectroscopy provides an invaluable tool for studying strongly correlated states, such as Wigner crystals and density waves, where exciton-electron interactions are modified by the emergence of charge order.
Carrier relaxation to quantum emitters in few-layer WSe2
Oreszczuk, Kacper; Kazimierczuk, Tomasz; Smolenski, Tomasz; et al. (2020)
Physical Review B
We present a detailed study of the time-resolved photoluminescence of narrow-line emission centers in WSe2 monolayers and bilayers. Our experiments reveal noninstantaneous photoluminescence intensity rise after the laser pulse. This shows that the simplest excitation model in which the localized states are directly populated by free excitons is not sufficient to fully reproduce experimental results. We, therefore, analyze a more complex phenomenological model where the relaxation of the carriers is mediated by long-lived intermediate states. Strong suppression of the lifetime of those intermediate states at elevated temperatures reveals their unique character, not matching any relaxed excitonic state in WSe2 monolayer. © 2020 American Physical Society
Interaction-Induced Shubnikov–de Haas Oscillations in Optical Conductivity of Monolayer MoSe2
Smolenski, Tomasz; Cotlet, Ovidiu; Popert, Alexander; et al. (2019)
Physical Review Letters
We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valley-polarized holes in the presence of a strong magnetic field. We find that exciton-hole interactions manifest themselves in hole-density dependent, Shubnikov–de Haas–like oscillations in the energy and line broadening of the excitonic resonances. These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, thus demonstrating that strong interactions between the excitons and Landau-quantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides.
Electrically tunable quantum confinement of neutral excitons
Thureja, Deepankur; Imamoglu, Atac; Smolenski, Tomasz; et al. (2022)
Nature
Confining particles to distances below their de Broglie wavelength discretizes their motional state. This fundamental effect is observed in many physical systems, ranging from electrons confined in atoms or quantum dots1,2 to ultracold atoms trapped in optical tweezers3,4. In solid-state photonics, a long-standing goal has been to achieve fully tunable quantum confinement of optically active electron–hole pairs, known as excitons. To confine excitons, existing approaches mainly rely on material modulation5, which suffers from poor control over the energy and position of trapping potentials. This has severely impeded the engineering of large-scale quantum photonic systems. Here we demonstrate electrically controlled quantum confinement of neutral excitons in 2D semiconductors. By combining gate-defined in-plane electric fields with inherent interactions between excitons and free charges in a lateral p–i–n junction, we achieve exciton confinement below 10 nm. Quantization of excitonic motion manifests in the measured optical response as a ladder of discrete voltage-dependent states below the continuum. Furthermore, we observe that our confining potentials lead to a strong modification of the relative wave function of excitons. Our technique provides an experimental route towards creating scalable arrays of identical single-photon sources and has wide-ranging implications for realizing strongly correlated photonic phases6,7 and on-chip optical quantum information processors8,9.
Optical Sensing of Fractional Quantum Hall Effect in Graphene
Popert, Alexander; Shimazaki, Yuya; Kroner, Martin; et al. (2022)
Nano Letters
Graphene and its heterostructures provide a unique and versatile playground for explorations of strongly correlated electronic phases, ranging from unconventional fractional quantum Hall (FQH) states in a monolayer system to a plethora of superconducting and insulating states in twisted bilayers. However, the access to those fascinating phases has been thus far entirely restricted to transport techniques, due to the lack of a robust energy bandgap that makes graphene hard to access optically. Here we demonstrate an all-optical, noninvasive spectroscopic tool for probing electronic correlations in graphene using excited Rydberg excitons in an adjacent transition metal dichalcogenide monolayer. These excitons are highly susceptible to the compressibility of graphene electrons, allowing us to detect the formation of odd-denominator FQH states at high magnetic fields. Owing to its submicron spatial resolution, the technique we demonstrate circumvents spatial inhomogeneities and paves the way for optical studies of correlated states in optically inactive atomically thin materials.
A simple state-of-the-art spectrometer for student labs: Cost-efficient, instructive, and widely applicable
Eggenberger, Andreas; Smolenski, Tomasz; Kroner, Martin (2024)
American Journal of Physics
We present a simple, cost-effective, yet instructive spectrometer for use in undergraduate instructional laboratory courses. Deliberate design choices are made to enhance the learning experience provided by the setup, where every component is accessible to students, allowing them to fully understand the function of each individual item. The result is a state-of-the-art spectrometer, built from commercially available components, which balances pedagogical simplicity with the potential for a wide range of applications. Our setup prepares students for future spectroscopy work in research labs. Furthermore, data-taking by means of a CCD camera and the subsequent analysis teach students fundamental computational skills. Within one image, the spectrometer can cover a spectral range of 40 nm and its spectral resolution is about 0.1 nm, limited by the imaging optics. Systematic uncertainties arising from mechanical play of the grating's rotation stage limit the reproducibility of the setup to 0.65 nm. While these parameters can be improved, we decided to maintain the pedagogical and straightforward nature of the presented setup, as any increase in cost or complexity would undermine its educational benefits. Using the spectrometer in an undergraduate instructional laboratory makes possible a variety of valuable experiments, such as calibration measurements, investigation of different types of uncertainties and measurements errors, and historically important measurements (e.g., the Balmer series or solar spectrum). We are convinced that the presented spectrometer will greatly benefit the learning experience of students for many years to come.
Temperature dependence of photoluminescence lifetime of atomically-thin WSe2 layer
Lopion, A.; Goryca, Mateusz; Smolenski, Tomasz; et al. (2020)
Nanotechnology
High-temperature kinetic magnetism in triangular lattices
Morera, Ivan; Kanász-Nagy, Márton; Smolenski, Tomasz; et al. (2023)
Physical Review Research
We study kinetic magnetism for the Fermi-Hubbard models in triangular type lattices, including a zigzag ladder, four- and six-legged triangular cylinders and a full two-dimensional triangular lattice. We focus on the regime of strong interactions, U≫t and filling factors around one electron per site. For temperatures well above the hopping strength, the Curie-Weiss form of the magnetic susceptibility suggests effective antiferromagnetic correlations for systems that are hole doped with respect to ν=1, and ferromagnetic correlations for systems with electron dopings. We show that these correlations arise from magnetic polaron dressing of charge carrier propagating in a spin incoherent Mott insulator. Effective interactions corresponding to these correlations can strongly exceed the magnetic super-exchange energy. In the case of hole doping, antiferromagnetic polarons originate from kinetic frustration of individual holes in a triangular lattice. In the case of electron doping, Nagaoka type ferromagnetic correlations are induced by propagating doublons. These results provide a theoretical explanation of recent experimental results in moire TMDC materials. To understand many-body states arising from antiferromagentic polarons at low temperatures, we study hole doped systems in finite magnetic fields. At low dopings and intermediate magnetic fields we find a magnetic polaron phase, separated from the fully polarized state by a metamagnetic transition. With decreasing magnetic field the system shows a tendency to phase separate, with hole rich regions forming antiferromagnetic spinbags. We demonstrate that direct observations of magnetic polarons in triangular lattices can be achieved in experiments with ultracold atoms, which allow measurements of three point hole-spin-spin correlations.
Kinetic magnetism in triangular moiré materials
Ciorciaro, Livio; Smolenski, Tomasz; Morera, Ivan; et al. (2023)
Nature
Magnetic properties of materials ranging from conventional ferromagnetic metals to strongly correlated materials such as cuprates originate from Coulomb exchange interactions. The existence of alternate mechanisms for magnetism that could naturally facilitate electrical control has been discussed theoretically, but an experimental demonstration in an extended system has been missing. Here we investigate MoSe₂/WS₂ van der Waals heterostructures in the vicinity of Mott insulator states of electrons forming a frustrated triangular lattice and observe direct evidence of magnetic correlations originating from a kinetic mechanism. By directly measuring electronic magnetization through the strength of the polarization-selective attractive polaron resonance, we find that when the Mott state is electron-doped, the system exhibits ferromagnetic correlations in agreement with the Nagaoka mechanism.
Electrically defined quantum dots for bosonic excitons
Thureja, Deepankur; Yazıcı, F. Emre; Smolenski, Tomasz; et al. (2024)
Physical Review B
Quantum dots are semiconductor nanostructures where particle motion is confined in all three spatial dimensions. Since their first experimental realization, nanocrystals confining the quanta of polarization waves, termed excitons, have found numerous applications in fields ranging from single photon sources for quantum information processing to commercial displays. A major limitation to further extending the range of potential applications has been the large inhomogeneity in, and lack-of tunability of, exciton energy that is generic to quantum dot materials. Here, we address this challenge by demonstrating electrically defined quantum dots for excitons in monolayer semiconductors where the discrete exciton energies can be tuned using applied gate voltages. Resonance fluorescence measurements show strong spectral jumps and blinking of these resonances, verifying their zero-dimensional nature. Our work paves the way for realizing quantum confined bosonic modes where nonlinear response would arise exclusively from exciton-exciton interactions.

Publications 1 - 10 of 13

Tomasz Smolenski

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