Emergent States in Photoinduced Charge-Density-Wave Transitions, 1st ed. 2021 Springer Theses Series

This book advances understanding of light-induced phase transitions and nonequilibrium orders that occur in a broken-symmetry system. Upon excitation with an intense laser pulse, materials can undergo a nonthermal transition through pathways different from those in equilibrium. The mechanism underlying these photoinduced phase transitions has long been researched, but many details in this ultrafast, non-adiabatic regime still remain to be clarified. The work in this book reveals new insights into this phenomena via investigation of photoinduced melting and recovery of charge density waves (CDWs). Using several time-resolved diffraction and spectroscopic techniques, the author shows that the light-induced melting of a CDW is characterized by dynamical slowing-down, while the restoration of the symmetry-breaking order features two distinct timescales: A fast recovery of the CDW amplitude is followed by a slower re-establishment of phase coherence, the latter of which is dictated by the presence of topological defects in the CDW. Furthermore, after the suppression of the original CDW by photoexcitation, a different, competing CDW transiently emerges, illustrating how a hidden order in equilibrium can be unleashed by a laser pulse. These insights into CDW systems may be carried over to other broken-symmetry states, such as superconductivity and magnetic ordering, bringing us one step closer towards manipulating phases of matter using a laser pulse.

Alfred Zong was awarded a PhD in Physics by Massachusetts Institute of Technology in 2020. He is currently a Miller Research Fellow at University of California, Berkeley. Dr. Zong’s research centers on studying photoinduced phase transitions and nonequilibrium ordering phenomena using time-resolved diffraction and spectroscopies.

Nominated as an outstanding PhD thesis by Massachusetts Institute of Technology

Includes an accessible introduction to the ultrafast science of quantum materials

Offers insights into photoinduced phase transitions and nonequilibrium orders in the ultrafast, non-adiabatic regime