Intra-OIST Research

SYMMETRY AND OPTICAL SELECTION RULES IN GRAPHENE QUANTUM DOTS

In collaboration with the Theory of Quantum Matter (Shannon) Unit

Nanoscale islands of graphene, referred to as Graphene Quantum Dots (GQDs), have garnered significant interest due to their potential applications and their ability to provide insights into the effects of confinement on graphene's distinct properties. Depending on their size, shape, and edge structure, GQDs exhibit optical properties that differ from those of extended graphene sheets. In this work, we have undertaken theoretical investigations to explore the influence of GQD size, shape, and edge structure (as depicted in the figure below) on their optical conductivity and optical selection rules. By examining these factors, we aim to gain a deeper understanding of how these fundamental characteristics impact the optical behavior of GQDs. This knowledge is crucial for both advancing our comprehension of graphene's confinement effects and unlocking the potential applications of GQDs in various fields.

Associated publication
R. Pohle, E. G. Kavousanaki, K. M. Dani, N. Shannon
Physical Review B 97, 115404 (2018)

SUPERCONDUCTIVITY IN DOPED WEYL SEMIMETALS

In collaboration with the Quantum Materials Science (Okada) Unit

Weyl semimetals, as three-dimensional topological and gapless materials, exhibit unique properties such as the presence of Fermi arcs on their surfaces and Weyl cones in the bulk. Interestingly, these materials can also host superconducting states, leading to the emergence of exotic topological superconductivity. In our collaborative research, we have focused on the experimental investigation of a doped Weyl semimetal, specifically on Se doped MoTe2, using Scanning Tunneling Microscopy (STM). We have identified the existence of a low-temperature Td phase in the material. By employing quasiparticle interference imaging, we have been able to visualize and study the properties of this phase. Our findings confirm the presence of global superconductivity within the system, as depicted in the figure below. Notably, we have determined that the superconducting coherence length exceeds the characteristic length scale of existing chemical disorder in the material. This discovery establishes the system as a robust superconductor even in the normal phase of the Weyl semimetal. Our findings contribute to the broader field of topological superconductivity and pave the way for future research and applications in this exciting area of study.

Associated publication
Z. Wang, J. Olivares, H. Namiki, V. Pareek, K. M. Dani, T. Sasagawa, V. Madhavan, Y. Okada
Physical Review B 104, 115102 (2021)

ON-DEMAND DRUG DELVIERY SYSTEM FOR CONTROL OF EPILEPSY

In collaboration with the Neurobiology Research (Wickens) Unit

Drug delivery systems play a crucial role in delivering drugs to specific target areas when needed, while minimizing their effects in non-target areas. These systems offer the potential to achieve high drug concentrations at specific sites while encapsulating the drug to limit unwanted actions elsewhere. In our collaborative research, we have focused on studying a novel drug delivery system that utilizes hollow-gold nanoparticles tethered to liposomes. Our investigation involved conducting proof-of-concept tests both in vivo and ex vivo. The drug delivery system we examined consists of hollow-gold nanoparticles that are attached to liposomes. When activated by optical or acoustic stimulation, these liposomes transiently become permeable. This allows for controlled release of the encapsulated drug at the desired target area. By conducting in vivo tests, we studied the system's performance and observed its effectiveness in delivering drugs to specific sites in a living organism. Additionally, ex vivo tests were carried out to further assess the system's functionality outside of a living organism.

This collaborative research effort has provided valuable insights into the potential of the hollow-gold nanoparticle-based drug delivery system. By leveraging optical or acoustic stimulation to trigger controlled drug release, we aim to enhance the precision and effectiveness of drug delivery while minimizing off-target effects. These findings have promising implications for the development of advanced drug delivery strategies with improved therapeutic outcomes.

Associated publication
T. Nakano, S. Rizwan, D. M. A. Myint, J. Gray, S. M. Mackay, P. Harris, C. G. Perk, B. I. Hyland, R. Empson, E. W. Tan, K. M. Dani, J. N. J. Reynolds, J. R. Wickens
Pharmaceutics 14, 468 (2022)