Applied Physics and Materials Science Special Seminar
Abstract:
In condensed-matter physics, the introduction of new degrees of freedom (DoFs) often leads to the emergence of complex and fascinating phenomena. Recently, advances in low-dimensional materials have enabled us to tailor electrons in strongly-correlated electron systems through electrostatic gating and the freedom of van der Waals stacking. These developments have raised an important question: are there hidden DoFs in these versatile material platforms that we have yet to discover?
In this seminar, I will discuss our exciting discovery of the moiré degree of freedom in 2D materials. This DoF originates from the twist angle in van der Waals stacks and opens up a new arena of correlated electronic phases. One of the most intriguing observations was the unconventional superconducting state that arises when two sheets of graphene are twisted at a magic angle of 1.1 degrees. Furthermore, our research revealed that this is just the beginning of an entire family of moiré superconductors, all of which exhibit rich and unusual phenomenology.
These findings have sparked a new field of study known as "twistronics", where we can now use moiré systems to study and create correlated quantum phenomena with unparalleled control. The physics of these moiré systems will also provide valuable insight into the understanding and creation of other quantum materials.
More about the Speaker:
Dr. Yuan Cao is a condensed matter physicist with a background in physics and electrical engineering. After earning his Bachelor's degree from the University of Science and Technology of China in 2014, he went on to pursue graduate studies at the Massachusetts Institute of Technology, where he earned his M.S. in 2016 and Ph.D. in 2020.
Dr. Cao's most significant contribution to the field is the development of a new experimental method for creating two layers of precisely twisted sheets of graphene. This groundbreaking research led to the discovery of exotic quantum phases, such as superconductivity, in graphene for the first time, and it has since opened up a new area of research that is now known as "twistronics". These achievements were recognized in 2018 when Dr. Cao was named as one of "Nature's 10", and his work was recognized as the Physics World 2018 Breakthrough of the Year. In recognition of his exceptional research, Dr. Cao was awarded the McMillan Award in 2021 and the Richard L. Greene Dissertation Award in 2022.
Dr. Cao is currently a Junior Fellow at Harvard University, where he continues to push the boundaries of our understanding of quantum materials and their potential for revolutionary technologies.