Tuning frustration in spin liquids by uniaxial pressure

• Applicants: Professor Dr. Philipp Gegenwart; Dr. Robert Küchler
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2014 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263806350

We explore novel quantum states of matter, in particular quantum spin liquids that arise due to strong geometrical frustration. Geometrical frustration is determined by the location of the atoms in the lattice and can hardly be varied in a controllable way without introducing disorder. Our entirely new experimental concept is to systematically vary geometrical frustration using uniaxial pressure and to detect with highest precision the linear thermal expansion down to very low temperature. This quantity is not only most sensitive to (magnetic) phase transitions but also to low-energy excitations, e.g. related to quantum criticality. Furthermore, as directional dependent probe of the entropy, it is ideally suited to investigate anisotropic properties of geometrically frustrated materials. Implementing the project requires the development of a uniaxial pressure dilatometer at the Max-Planck Institute CPFS in Dresden, as well as its application to single crystals of prototype materials, characterized at Augsburg University. Our main goal is to use uniaxial pressure for modifying geometrical frustration, tuning systems into novel quantum spin liquid states, as well as exploring the sensitivity of quantum spin liquids to symmetry-breaking distortions.

• DFG Programme: Research Grants