Shot noise measurement in magic-angle twisted bilayer graphene

Magic-angle twisted bilayer graphene (MATBG) is a superconducting material known to exhibit linear electrical resistivity across a range of temperatures. This unusual linear in T property makes MATBG an appealing platform for investigating possible strange metal phase behavior. The discrete nature of charge carriers generates shot noise, which can provide information about the charge quantization and interactions between charge carriers. In a strange metal phase without quasiparticle excitation, the shot noise Fano factor is expected to be suppressed from the Fermi liquid counterpart. To measure the shot noise, the MATBG device is cooled to 4K in a 4He Dewar. A low temperature cryostat maintains these conditions while the device's signal is passed through 2 stages of amplification at room temperature before being measured. The cross-correlation power spectrum density is computed to analyze the noise. Characterizing the shot noise will offer further insight into electron scattering dynamics in moiré pattern structures like MATBG. This talk would focus specifically on the signal processing and iterative averaging strategies used to find more accurate values for Johnson noise and consequently, values for shot noise.