Statistics of Conductance Fluctuations in 2D systems

Abstract

Study of 2D materials is interesting due to the various phase transitions observed in these materials. I shall present the results obtained in the study of phase transi tions in three different 2D material systems – monolayer graphene in integer quan tum Hall (IQH) regime, topological surface states (TSS) of 3D topological insulator (TI) BiSbTeSe2 (BSTS), and a thin film of rare-earth nickelate with composition (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)NiO3 ([LPNSE]NO). First, I shall talk about the conductance fluctuations in IQH transition in mono layer graphene. The results shall provide the first experimental evidence for the the oretical prediction that observables such as conductance fluctuations are multifractal in an Anderson localization-delocalization transition [1]. Next, I shall discuss the measured universal conductance fluctuations (UCF) aris ing from the TSS of BSTS and show that the UCF is multifractal at low temperatures thus proving the theoretical prediction that in the presence of electron-electron inter actions, the TSS of a 3D TI exists at Anderson criticality. Finally, I shall discuss the phase transitions in [LPNSE]NO thin films probed through resistance fluctuations spectroscopy measurements in the temperature range 80 K to 240 K. The results establish the co-existence of two phase transitions (metal insulator and magnetic Néel transitions) in this sample in the temperature window un der consideration and demonstrate the existence of an electronically phase-separated regime [2].