Transition-metal dichalcogenides (TMDs) exhibit a phase diagram in which a multitude of charge density wave (CDW) orders can coexist and/or compete with superconductivity. Despite extensive studies over the last decade, the mechanisms of CDWs and superconductivity in TMDs are still under debate. In the first part of the colloquium, I will provide a review of CDW in MDs. I will then discuss our recent observations of dynamically modulated quantum phase transition between two distinct charge density wave (CDW) phases in two-dimensional 2H-NbSe2. We find a surprising evolution of the conductance fluctuation spectra across the CDW temperature: the conductance fluctuates between two precise values,separated by a quantum of conductance. With the help of mean-field calculations, these observations could be explained as to arise from dynamical phase transition between the two CDW states. The results resolve a long-standing mystery of the anomalously large spectroscopic gap in NbSe2. I will also discuss our recent results on observation of signatures of pseudogap state at temperatures above TCDW in two-dimensional 2H-NbSe2. These results might explain the difference in the CDW transition temperature inferred from transport and Raman spectroscopy measurements.
Aveek Bid did his Ph.D in Physics at Indian Institute of Science, Bangalore. After his post-doctoral work at Weizmann Institute of Science, Israel he returned to his alma mater as assistant professor in the year 2010, where he is now an associate professor. Aveek Bid has received several awards and fellowships in recognition of his research work. These include Swarnajayanti Fellowship from DST, India (2017), Feinberg Graduate School Fellowship for postdoctoral studies at Weizmann Institute of Science and Shyama Prasad Mukherjee Memorial fellowship awarded by CSIR, India. His recent research interests include electrical transport in 2D van der Waals heterostructures, graphene, topological insulators and ultrathin nanowires and superconductivity and charge density wave in low dimensional systems.