Cryogen-free dilution refrigerator with 14T magnet for high-field studies of quantum materials

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Quantum materials are novel systems, engineered in laboratories, which host strong enough electronic interactions to display quantum phenomena such as superconductivity, correlated insulating states and magnetism with tremendous technological applications. These phenomena emerge when the electronic interaction dominate over the thermal fluctuations of the system, i.e. at milliKelvin temperatures. Experimentally, these temperatures are reached in dilution refrigerator systems. Consequently, we aim to add such a dilution refrigerator, capable of a base temperature of 10 mK (and stability below 5mK) and equipped with a 14T superconducting magnet, to the LMU’s experimental capabilities. This system, absent from the current apparatus of the LMU, will be dedicated to the study of said quantum materials. This acquisition is paramount to secure a competitive position for our institution, and more precisely its Chair of Solid State Physics, on this timely subject. The ultra-high 14T magnetic field will allow us to introduce a new quantizing energy scale to the material, and thus to tune the electronic interaction. In particular, this field will be high enough to condense all the electronic carriers of a variety of quantum materials into a single energy level, causing the electronic spectrum to become analogous to a one-dimensional system which is highly sensitive to pertubations. Attaining this ultra-quantum limit permits the emergence of novel phenomena such as charge/spin density waves and quantum Hall effect. This refrigerator system will thus open completely new axis of research at the LMU. We will probe the electronic response to the temperature and field constraints through 48 highly-filtered DC transmission lines designed to suppress electromagnetic heating of the electrons with an output integrated in our measurement setup made of an array of DC pre-amplifiers and lock-in amplifiers. The additional sample rotator will expand the operational area, whereby the magnetic field can be applied arbitrary with respect to the sample surface. The fast loading mechanism is crucial to optimize our usage of this system by greatly reducing loading times. Finally, we wish to buy a cryogen-free system both for its simplicity of usage, as we plan to grant access to the equipment across several chairs of the LMU as well as the Munich Quantum Valley initiative, and for the long-term economies it permits in light of the ever increasing price of liquid helium.