PAR Ann-Kathrin AUDREN To my parents Beate and Theo and my brother Tobias and my husband Benjamin Acknowledgements It was almost four years ago that I started the PhD work at EPFL. At that time I remember myself having only a vague idea what the work of an experimental physicist looked like. In retrospect, I am very grateful and happy that I decided for this particular thesis subject, since it allowed me to merge high quality experimental data, simulations and a theoretical description of a

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... lex process. The outcome of this project depended on many other people, without them it would not have been possible. Therefore, I am glad about the support and help from many people throughout these four years. First of all, I would like to express my thanks to both the thesis directors Prof. Robert Schaller and Dr. Daniele Mari. They were a complementary team in guiding my thesis work and I never had the feeling to be sitting between two chairs. Robert Schaller not only proposed the project but also guided me through it, even after his official retirement one year ago. He convinced me that mechanical spectroscopy is a beautiful and extremely powerful technique to study complicated materials. I admire him for his extensive knowledge of the physics of material and for his intuition, in which direction the research should be focused. I am very grateful for the fruitful discussions that opened new doors for further research and from which I learned plenty of things. Thank you very much for the good collaboration. I am equally grateful to my other supervisor, Daniele Mari. I have profited on many occasions from his open door in order to engage him in spontaneous discussions. Thanks to his detailed knowledge and experimental know-how, he helped me a lot in my every-day research activity. He has a good ability to distinguish between the necessity of deadlines in order to get a project done and the necessary freedom to be able to develop new ideas. I appreciated this a lot during my time here.