Strain Tuning the Electronic Ground State in Rare Earth Nickelate Membranes

The ground state of rare earth nickelates (RENiO₃) is characterized by rich electronic phenomena that strongly couple to lattice degrees of freedom. One well-known example is the bandwidth control of the insulator-to-metal transition (IMT) across different rare earth elements (1). Advances in freestanding oxide membranes allow versatile control of lattice strain beyond bulk limits (2, 3). In this talk, I present our efforts to integrate in-situ strain tuning capability on oxide freestanding membranes with multiple synchrotron probes. Using a prototypical RENiO₃ membranes, we conducted soft x-ray spectroscopy with in- situ tunable uniaxial strain. A systematic evolution of the XAS and RIXS spectra were observed, which highlights the interplay between lattice degrees of freedom and electronic structure, presumably important to the mechanism of IMT transition. Our work opens new opportunities into controlled strain engineering on low dimensional quantum materials for novel electronic devices.