Shot noise measurements in strongly correlated materials
Doctor of Philosophy
In conventional metals where the interaction between electrons is weak, the low energy excitations can be well explained by Landau Fermi liquid theory. However, in many metallic materials with bulk d or f-electrons, such as transition metal oxides, conventional theories fail to effectively describe the electronic or spin properties due to the presence of strong electron-electron interactions. A better understanding of electronic behavior in strongly correlated systems has been a great challenge in modern physics. In this dissertation, I mainly focused on the studying of quasiparticle's effective charge in strongly correlated material by probing the shot noise--a current fuctuation that originates from the discrete nature of charge carriers. We firstly explored methods for fabricating tunnel junctions and found that hexagonal boron nitride (hBN) is a very good candidate for a tunneling barrier. The tunneling device made by Au/hBN/Au has well-behaved shot noise properties that match with single-particle tunneling predictions quantitatively. Shot noise is also studied in highquality LSCO/LCO/LSCO tunnel structures grown by the molecular beam epitaxy (MBE) technique at various doping levels from underdoped to nearly optimum doped. In those devices, the shot noise is found to be larger than single-electron tunneling prediction deep into the pseudogap region of temperature and bias, indicating pairing might exist in the pseudogap phase.