Quantum Phase Transitions in SrCu2(BO3)2 and NiS2 Revealed by X-rays and Transport
Quantum phase transitions (QPT) are fundamentally different from their classical counterparts, mixing statics and dynamics. I will describe our experimental approaches to two such QPTs. In the first part, I will show that the precise measurement of lattice distortions can reveal information about magnetic phase transitions in a material with strong spin-lattice coupling. Combining synchrotron x-ray and diamond anvl celltechniques, we consider a set of interacting dimers on a square lattice to uncover the magnetic phase diagram of the Shastry-Sutherland model in SrCu2(BO3)2.
For the second part, I will consider quantum criticality at a Mott-Hubbard metal-insulator transition in NiS2. We have used x-ray diffraction to track magnetism and lattice symmetry to showthat neither plays a driving role at the phase transition, and that the transition is solely driven by electronic correlations. Finally, we explore the critical region of the phase transition in search for scaling laws using high-pressure transport measurements.