@article{61257,
  abstract     = {{<jats:p>Exceptional points (EPs), with their intriguing spectral topology, have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field. Here, we investigate spectral topology and EPs in systems with significant nonlinearity, exemplified by a nonequilibrium exciton-polariton condensate. With the possibility to control loss and gain and nonlinearity by optical means, this system allows for a comprehensive analysis of the interplay of nonlinearities (Kerr type and saturable gain) and non-Hermiticity. Not only do we find that EPs can be intentionally shifted in parameter space by the saturable gain, but we also observe intriguing rotations and intersections of Riemann surfaces and find nonlinearity-enhanced sensing capabilities. With this, our results illustrate the potential of tailoring spectral topology and related phenomena in non-Hermitian systems by nonlinearity.</jats:p>
          <jats:sec>
            <jats:title/>
            <jats:supplementary-material>
              <jats:permissions>
                <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement>
                <jats:copyright-year>2024</jats:copyright-year>
              </jats:permissions>
            </jats:supplementary-material>
          </jats:sec>}},
  author       = {{Wingenbach, Jan and Schumacher, Stefan and Ma, Xuekai}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Manipulating spectral topology and exceptional points by nonlinearity in non-Hermitian polariton systems}}},
  doi          = {{10.1103/physrevresearch.6.013148}},
  volume       = {{6}},
  year         = {{2024}},
}

@article{61258,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>Thermal stability is crucial for doped organic semiconductors (OSCs) and their applications in organic thermoelectric (OTE) devices. However, the capacity of n‐dopants to produce thermally stable n‐doped OSC films has not been thoroughly explored, with few reports of high thermal stability. Here, a novel n‐dopant, phosphazenium tetrafluoroborate (P<jats:sub>2</jats:sub>BF<jats:sub>4</jats:sub>) is introduced, which effectively induces n‐doping in N2200, P(PzDPP‐CT2) and several other commonly used OSCs. Remarkably, the electrical conductivity of P<jats:sub>2</jats:sub>BF<jats:sub>4</jats:sub>‐doped OSC films remains almost unchanged even after heating at temperatures &gt; 150 °C for 24 h, far superior to the films doped with benchmark N‐DMBI. The exceptional thermal stability observed in P<jats:sub>2</jats:sub>BF<jats:sub>4</jats:sub>‐doped P(PzDPP‐CT2) films allows for stable operation of the corresponding organic thermoelectric devices at 150 °C for 16 h, a milestone not previously achieved. This study offers valuable insights into the development of n‐dopants capable of producing OSCs with outstanding thermal stability, paving the way for the practical realization of OTE devices with enhanced operation stability.</jats:p>}},
  author       = {{Wei, Huan and Guo, Jing and Liu, Heng and Wu, Tong and Chen, Ping‐An and Dong, Chuanding and Wang, Shu‐Jen and Schumacher, Stefan and Bai, Yugang and Lei, Ting and Wang, Suhao and Hu, Yuanyuan}},
  issn         = {{2199-160X}},
  journal      = {{Advanced Electronic Materials}},
  publisher    = {{Wiley}},
  title        = {{{Novel Phosphazenium Tetrafluoroborate Dopant Enables Efficient and Thermally Stable n‐Doped Organic Semiconductors}}},
  doi          = {{10.1002/aelm.202400767}},
  year         = {{2024}},
}

@article{61259,
  author       = {{Bauch, Fabian and Dong, Chuan-Ding and Schumacher, Stefan}},
  issn         = {{1932-7447}},
  journal      = {{The Journal of Physical Chemistry C}},
  number       = {{8}},
  pages        = {{3525--3532}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Dynamics of Electron–Hole Coulomb Attractive Energy and Dipole Moment of Hot Excitons in Donor–Acceptor Polymers}}},
  doi          = {{10.1021/acs.jpcc.3c07513}},
  volume       = {{128}},
  year         = {{2024}},
}

@article{61263,
  abstract     = {{<jats:p>Charge transfer mechanism in the deprotonation-induced n-type doping of PCBM.</jats:p>}},
  author       = {{Dong, Chuan-Ding and Bauch, Fabian and Hu, Yuanyuan and Schumacher, Stefan}},
  issn         = {{1463-9076}},
  journal      = {{Physical Chemistry Chemical Physics}},
  number       = {{5}},
  pages        = {{4194--4199}},
  publisher    = {{Royal Society of Chemistry (RSC)}},
  title        = {{{Charge transfer in superbase n-type doping of PCBM induced by deprotonation}}},
  doi          = {{10.1039/d3cp05105f}},
  volume       = {{26}},
  year         = {{2024}},
}

@article{61261,
  author       = {{Liang, Qian and Ma, Xuekai and Gu, Chunling and Ren, Jiahuan and An, Cunbin and Fu, Hongbing and Schumacher, Stefan and Liao, Qing}},
  issn         = {{0002-7863}},
  journal      = {{Journal of the American Chemical Society}},
  number       = {{7}},
  pages        = {{4542--4548}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Photochemical Reaction Enabling the Engineering of Photonic Spin–Orbit Coupling in Organic-Crystal Optical Microcavities}}},
  doi          = {{10.1021/jacs.3c11373}},
  volume       = {{146}},
  year         = {{2024}},
}

@article{62868,
  abstract     = {{<jats:p>We theoretically investigate strategies for the deterministic creation of trains of time-bin entangled photons using an individual quantum emitter described by a Λ-type electronic system. We explicitly demonstrate the theoretical generation of linear cluster states with substantial numbers of entangled photonic qubits in full microscopic numerical simulations. The underlying scheme is based on the manipulation of ground state coherences through precise optical driving. One important finding is that the most easily accessible quality metrics, the achievable rotation fidelities, fall short in assessing the actual quantum correlations of the emitted photons in the face of losses. To address this, we explicitly calculate stabilizer generator expectation values as a superior gauge for the quantum properties of the generated many-photon state. With widespread applicability in other emitter and excitation–emission schemes also, our work lays the conceptual foundations for an in-depth practical analysis of time-bin entanglement based on full numerical simulations with predictive capabilities for realistic systems and setups, including losses and imperfections. The specific results shown in the present work illustrate that with controlled minimization of losses and realistic system parameters for quantum-dot type systems, useful linear cluster states of significant lengths can be generated in the calculations, discussing the possibility of scalability for quantum information processing endeavors.</jats:p>}},
  author       = {{Bauch, David and Köcher, Nikolas and Heinisch, Nils and Schumacher, Stefan}},
  issn         = {{2835-0103}},
  journal      = {{APL Quantum}},
  number       = {{3}},
  publisher    = {{AIP Publishing}},
  title        = {{{Time-bin entanglement in the deterministic generation of linear photonic cluster states}}},
  doi          = {{10.1063/5.0214197}},
  volume       = {{1}},
  year         = {{2024}},
}

@unpublished{62858,
  abstract     = {{Phonons in solid-state quantum emitters play a crucial role in their performance as photon sources in quantum technology. For resonant driving, phonons dampen the Rabi oscillations resulting in reduced preparation fidelities. The phonon spectral density, which quantifies the strength of the carrier-phonon interaction, is non-monotonous as a function of energy. As one of the most prominent consequences, this leads to the reappearance of Rabi rotations for increasing pulse power, which was theoretically predicted in Phys. Rev. Lett. 98, 227403 (2007). In this paper we present the experimental demonstration of the reappearance of Rabi rotations.}},
  author       = {{Hanschke, L. and Bracht, T. K. and Schöll, E. and Bauch, David and Berger, Eva and Kallert, Patricia and Peter, M. and Garcia, A. J. and Silva, S. F. Covre da and Manna, S. and Rastelli, A. and Schumacher, Stefan and Reiter, D. E. and Jöns, Klaus}},
  booktitle    = {{arXiv:2409.19167}},
  title        = {{{Experimental measurement of the reappearance of Rabi rotations in semiconductor quantum dots}}},
  year         = {{2024}},
}

@article{48599,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>The biexciton‐exciton emission cascade commonly used in quantum‐dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work, it focuses on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishability. It achieves this goal by selectively reducing the biexciton lifetime with an optical resonator. It demonstrates that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and twofold degenerate optical modes. The in‐depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum‐dot cavity excitation dynamics with full access to photon properties. It reports non‐trivial dependencies on system parameters and use the predictive power of the combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values, here specifically for the telecom C‐band at 1550 nm.</jats:p>}},
  author       = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}},
  issn         = {{2511-9044}},
  journal      = {{Advanced Quantum Technologies}},
  keywords     = {{tet_topic_qd}},
  publisher    = {{Wiley}},
  title        = {{{On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs}}},
  doi          = {{10.1002/qute.202300142}},
  year         = {{2023}},
}

@unpublished{43246,
  abstract     = {{The biexciton-exciton emission cascade commonly used in quantum-dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work we focus on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishibility. We achieve this goal by selectively reducing the biexciton lifetime with an optical resonator. We demonstrate that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and two-fold degenerate optical modes. Our in-depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum-dot cavity excitation dynamics with full access to photon properties. We report non-trivial dependencies on system parameters and use the predictive power of our combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values in the telecom C-band at $1550\,\mathrm{nm}$.}},
  author       = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}},
  keywords     = {{tet_topic_phc, tet_topic_qd}},
  title        = {{{On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs}}},
  year         = {{2023}},
}

@article{51093,
  abstract     = {{<jats:p>Dynamics-induced interchain charge transfer in a polymer aggregate in stack configuration can be understood by single-oligomer polaron energy.</jats:p>}},
  author       = {{Bauch, Fabian and Dong, Chuan-Ding and Schumacher, Stefan}},
  issn         = {{2050-7526}},
  journal      = {{Journal of Materials Chemistry C}},
  keywords     = {{Materials Chemistry, General Chemistry}},
  number       = {{38}},
  pages        = {{12992--12998}},
  publisher    = {{Royal Society of Chemistry (RSC)}},
  title        = {{{Dynamics-induced charge transfer in semiconducting conjugated polymers}}},
  doi          = {{10.1039/d3tc02263c}},
  volume       = {{11}},
  year         = {{2023}},
}

@article{35160,
  author       = {{Jia, Jichao and Cao, Xue and Ma, Xuekai and De, Jianbo and Yao, Jiannian and Schumacher, Stefan and Liao, Qing and Fu, Hongbing}},
  issn         = {{2041-1723}},
  journal      = {{Nature Communications}},
  keywords     = {{General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}},
  number       = {{1}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Circularly polarized electroluminescence from a single-crystal organic microcavity light-emitting diode based on photonic spin-orbit interactions}}},
  doi          = {{10.1038/s41467-022-35745-w}},
  volume       = {{14}},
  year         = {{2023}},
}

@article{42973,
  author       = {{Lüders, Carolin and Pukrop, Matthias and Barkhausen, Franziska and Rozas, Elena and Schneider, Christian and Höfling, Sven and Sperling, Jan and Schumacher, Stefan and Aßmann, Marc}},
  issn         = {{0031-9007}},
  journal      = {{Physical Review Letters}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{11}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Tracking Quantum Coherence in Polariton Condensates with Time-Resolved Tomography}}},
  doi          = {{10.1103/physrevlett.130.113601}},
  volume       = {{130}},
  year         = {{2023}},
}

@article{61252,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>The biexciton‐exciton emission cascade commonly used in quantum‐dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work, it focuses on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishability. It achieves this goal by selectively reducing the biexciton lifetime with an optical resonator. It demonstrates that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and twofold degenerate optical modes. The in‐depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum‐dot cavity excitation dynamics with full access to photon properties. It reports non‐trivial dependencies on system parameters and use the predictive power of the combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values, here specifically for the telecom C‐band at 1550 nm.</jats:p>}},
  author       = {{Bauch, David and Siebert, Dustin and Jöns, Klaus D. and Förstner, Jens and Schumacher, Stefan}},
  issn         = {{2511-9044}},
  journal      = {{Advanced Quantum Technologies}},
  number       = {{1}},
  publisher    = {{Wiley}},
  title        = {{{On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs}}},
  doi          = {{10.1002/qute.202300142}},
  volume       = {{7}},
  year         = {{2023}},
}

@article{61266,
  abstract     = {{<jats:p>This review examines the use of continuous-variable spectroscopy techniques for investigating quantum coherence and light-matter interactions in semiconductor systems with ultrafast dynamics. Special emphasis is placed on multichannel homodyne detection as a powerful tool to measure the quantum coherence and the full density matrix of a polariton system. Observations, such as coherence times that exceed the nanosecond scale obtained by monitoring the temporal decay of quantum coherence in a polariton condensate, are discussed. Proof-of-concept experiments and numerical simulations that demonstrate the enhanced resourcefulness of the produced system states for modern quantum protocols are assessed. The combination of tailored resource quantifiers and ultrafast spectroscopy techniques that have recently been demonstrated paves the way for future applications of quantum information technologies.</jats:p>}},
  author       = {{Lüders, Carolin and Barkhausen, Franziska and Pukrop, Matthias and Rozas, Elena and Sperling, Jan and Schumacher, Stefan and Aßmann, Marc}},
  issn         = {{2159-3930}},
  journal      = {{Optical Materials Express}},
  number       = {{11}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Continuous-variable quantum optics and resource theory for ultrafast semiconductor spectroscopy [Invited]}}},
  doi          = {{10.1364/ome.497006}},
  volume       = {{13}},
  year         = {{2023}},
}

@article{61264,
  author       = {{Yu, Yueyang and Dong, Chuan-Ding and Binder, Rolf and Schumacher, Stefan and Ning, Cun-Zheng}},
  issn         = {{1936-0851}},
  journal      = {{ACS Nano}},
  number       = {{5}},
  pages        = {{4230--4238}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Strain-Induced Indirect-to-Direct Bandgap Transition, Photoluminescence Enhancement, and Linewidth Reduction in Bilayer MoTe<sub>2</sub>}}},
  doi          = {{10.1021/acsnano.2c01665}},
  volume       = {{17}},
  year         = {{2023}},
}

@article{61269,
  author       = {{Gao, Ying and Ma, Xuekai and Zhai, Xiaokun and Xing, Chunzi and Gao, Meini and Dai, Haitao and Wu, Hao and Liu, Tong and Ren, Yuan and Wang, Xiao and Pan, Anlian and Hu, Wei and Schumacher, Stefan and Gao, Tingge}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  number       = {{20}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Single-shot spatial instability and electric control of polariton condensates at room temperature}}},
  doi          = {{10.1103/physrevb.108.205303}},
  volume       = {{108}},
  year         = {{2023}},
}

@article{61267,
  abstract     = {{<jats:p>Dynamics-induced interchain charge transfer in a polymer aggregate in stack configuration can be understood by single-oligomer polaron energy.</jats:p>}},
  author       = {{Bauch, Fabian and Dong, Chuan-Ding and Schumacher, Stefan}},
  issn         = {{2050-7526}},
  journal      = {{Journal of Materials Chemistry C}},
  number       = {{38}},
  pages        = {{12992--12998}},
  publisher    = {{Royal Society of Chemistry (RSC)}},
  title        = {{{Dynamics-induced charge transfer in semiconducting conjugated polymers}}},
  doi          = {{10.1039/d3tc02263c}},
  volume       = {{11}},
  year         = {{2023}},
}

@article{40274,
  author       = {{Zhai, Xiaokun and Ma, Xuekai and Gao, Ying and Xing, Chunzi and Gao, Meini and Dai, Haitao and Wang, Xiao and Pan, Anlian and Schumacher, Stefan and Gao, Tingge}},
  journal      = {{Physical Review Letters}},
  number       = {{13}},
  pages        = {{136901}},
  title        = {{{Electrically controlling vortices in a neutral exciton polariton condensate at room temperature}}},
  doi          = {{10.1103/PhysRevLett.131.136901}},
  volume       = {{131}},
  year         = {{2023}},
}

@article{36416,
  author       = {{De, Jianbo and Ma, Xuekai and Yin, Fan and Ren, Jiahuan and Yao, Jiannian and Schumacher, Stefan and Liao, Qing and Fu, Hongbing and Malpuech, Guillaume and Solnyshkov, Dmitry}},
  issn         = {{0002-7863}},
  journal      = {{Journal of the American Chemical Society (JACS)}},
  keywords     = {{Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}},
  number       = {{3}},
  pages        = {{1557--1563}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Room-Temperature Electrical Field-Enhanced Ultrafast Switch in Organic Microcavity Polariton Condensates}}},
  doi          = {{10.1021/jacs.2c07557}},
  volume       = {{145}},
  year         = {{2023}},
}

@article{51092,
  abstract     = {{<jats:p>Lewis-acid doping of organic semiconductors (OSCs) opens up new ways of p-type doping and has recently become of significant interest.</jats:p>}},
  author       = {{Bauch, Fabian and Dong, Chuan-Ding and Schumacher, Stefan}},
  issn         = {{2046-2069}},
  journal      = {{RSC Advances}},
  keywords     = {{General Chemical Engineering, General Chemistry}},
  number       = {{22}},
  pages        = {{13999--14006}},
  publisher    = {{Royal Society of Chemistry (RSC)}},
  title        = {{{Protonation-induced charge transfer and polaron formation in organic semiconductors doped by Lewis acids}}},
  doi          = {{10.1039/d2ra02032g}},
  volume       = {{12}},
  year         = {{2022}},
}