Browsing by Author "Biesner, Tobias"

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    Pressure-tuned interactions in frustrated magnets : pathway to quantum spin liquids?
    (2019) Biesner, Tobias; Uykur, Ece
    Quantum spin liquids are prime examples of strongly entangled phases of matter with unconventional exotic excitations. Here, strong quantum fluctuations prohibit the freezing of the spin system. On the other hand, frustrated magnets, the proper platforms to search for the quantum spin liquid candidates, still show a magnetic ground state in most of the cases. Pressure is an effective tuning parameter of structural properties and electronic correlations. Nevertheless, the ability to influence the magnetic phases should not be forgotten. We review experimental progress in the field of pressure-tuned magnetic interactions in candidate systems. Elaborating on the possibility of tuned quantum phase transitions, we further show that chemical or external pressure is a suitable parameter in these exotic states of matter.
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    Spectroscopic investigations of kagome - honeycomb quantum magnets
    (2022) Biesner, Tobias; Dressel, Martin (Prof. Dr.)
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    Spectroscopic trace of the Lifshitz transition and multivalley activation in thermoelectric SnSe under high pressure
    (2021) Biesner, Tobias; Li, Weiwu; Tsirlin, Alexander A.; Roh, Seulki; Wei, Pai-Chun; Uykur, Ece; Dressel, Martin
    Multivalley systems offer not only exciting physical phenomena but also the possibility of broad utilization. Identifying an important platform and understanding its physics are paramount tasks to improve their capability for application. Here, we investigate a promising candidate, the semiconductor SnSe, by optical spectroscopy and density functional theory calculations. Upon applying pressure to lightly doped SnSe, we directly monitored the phase transition from semiconductor to semimetal. In addition, heavily doped SnSe exhibited a successive Lifshitz transition, activating multivalley physics. Our comprehensive study provides insight into the effects of pressure and doping on this system, leading to promising routes to tune the material properties for advanced device applications, including thermoelectrics and valleytronics.