In the world of condensed matter physics, the concept of fractionalization has long been a dream for many researchers. This phenomena refers to a collective state of electrons in which they carry a charge that is a fraction of the electron charge, all without the presence of a magnetic field. This breakthrough has significant implications not only for intellectual exploration but also for potential technological applications, such as quantum computing.
Traditionally, physicists have achieved fractionalization by using magnetic fields to suppress kinetic energy, resulting in the celebrated fractional quantum Hall effect. However, the reliance on specialized labs equipped with strong magnetic fields has limited progress in this area. Therefore, the research conducted by the Kim Group, led by Professor Eun-Ah Kim from the College of Arts and Sciences at Cornell University, aims to uncover strategies for achieving fractionalization without the need for a magnetic field.
The Kim Group takes an unconventional approach by leveraging geometric thinking in a twisted bilayer graphene (TBG) lattice. This unique lattice structure provides an opportunity to predict new effects and explore the possibility of fractional correlated insulator phases. Unlike traditional studies of charge distribution, where electron wave functions are isotropic clouds centered at lattice sites, the electron wave functions in moiré graphene systems are spread over multiple moiré lattice sites and take on an anisotropic, three-leaf clover shape.
Through their research, the Kim Group has proposed the existence of fractional correlated insulator phases with distinct properties:
– Excitations or particles in these phases carry fractional electric charges, a hallmark of fractionalization.
– Some of these fractional excitations exhibit “fractonic” behavior, meaning they can only move in certain directions.
– An emergent symmetry has been identified, playing a crucial role in unifying the behavior of these fractional excitations.
The discovery of fractionalization without a magnetic field presents the field of condensed matter physics with a new setting for exploring novel theoretical concepts, such as emergent symmetries and fractonic dynamics. However, Professor Kim emphasizes that this is only the beginning, and the researchers have merely scratched the surface of this fascinating phenomenon.
To validate their predictions and further explore the possibilities of fractionalization, the Kim Group is collaborating with experimental colleagues. These collaborations aim to confirm the existence of fractional correlated insulator phases experimentally and delve deeper into the emergent symmetries and fractonic dynamics that underpin this phenomenon. It is through these collaborative efforts that the true potential of fractionalization in condensed matter physics can be realized.
The pursuit of observing fractionalization in condensed matter physics has captivated the imaginations of many researchers. Now, with the possibility of achieving it without the need for a magnetic field, the field is set to enter a new era of exploration. Professor Eun-Ah Kim and her team’s groundbreaking research on fractional correlated insulator phases in twisted bilayer graphene opens the doors to a wealth of theoretical and practical advancements. As they say, this is only the beginning, and there is still much more to discover and understand about this fascinating phenomenon.