Seven scientists who are at the forefront of quantum materials research will deliver their talks online. They will accept the questions from participants after each talk.
How to watch?
An overview is presented for recent development of graphene NEMS (Nano-Electro-Mechanical Systems) technology for extreme sensing and novel thermal engineering applications. Three-terminal switches with heterogeneously stacked graphene / h-BN layers are developed, which achieve low-voltage and sub-thermal switching (S << 60 mV/dec). We then present graphene chemical gas sensors, which detect either resistance or mass changes due to a small number of gas molecules physisorbed onto suspended graphene at room temperature. We also show our recent attempt of single-nanometer-scale patterning of suspended graphene by using focused helium ion beam for nanoscale thermal devices such as a thermal rectifier.
Hexagonal boron nitride is a kind of van der Waals layered materials, in which each layer is composed of an atomically flat layer with sp2 bonding between boron and nitrogen atoms, and the inter layers are weekly coupled via the van der Waals interaction. Originating from the strongly anisotropic 2D crystal structure, this material shows very interesting optical properties, such a high luminous efficiency of exciton in the far-UV region at room temperature. We will focus on the peculiar optical properties and discuss the mechanism of the efficient luminescence.
The droplet epitaxy technique is a scheme to create quantum dots, i.e., semiconductor nanoparticles with typical sizes around 10-100 nm. The technique was invented by Nobuyuki Koguchi in National Research Institute for Metals (former NIMS) in 1990, and now regarded worldwide as an alternative approach to self-assembling high-quality quantum dots, which are suitable for various quantum applications. In this talk I review progress on the development of novel quantum light sources based on our droplet epitaxy technology.
The diamond NV center is expected to be applied to high-sensitivity quantum magnetic sensors. The excellent spin characteristics are derived from the physical properties of diamond as a high-temperature material, and it has already been reported that the spin coherence time at room temperature exceeds 2 ms. In order to improve the sensitivity, it is indispensable to improve the crystalline quality and appropriately form the NV centers. In this talk, we will focus on the research conducted at NIMS regarding diamond crystal growth for the purpose of quantum magnetic sensor application.
Topological materials have been attracting much interest in condensed matter physics. To date, thousands of materials have been identified to be topological by combining theories on topological materials with materials databases. Meanwhile, apart from such automated searches, we need deeper understanding on their topological nature. In this talk, we explain a series of our works to understand their origins from various theoretical viewpoints. For example, studies on topological-nontopological phase transitions have shown us new classes of topological materials called topological semimetals, which have been established among the family of topological materials. Such an understanding leads us to renewed interests in various known materials.
Topological classification of materials is a new paradigm in the field of materials science. Topologically-nontrivial materials may offer revolutionary functionalities. Topologically-protected surface states may find application in future electronics. Majorana-fermion-based topological quantum computing is one of long-term targets in topological materials research. In this talk, I will introduce basic research into topological materials and vortex manipulation we are conducting at the NIMS.
It is known that in 3D chiral Weyl fermion becomes possible only when mass is zero. In this talk, we highlight the possibility of massive chiral quasiparticle in 2D, and unveil its physical consequence. When honeycomb lattice is distorted in Kekulé ways respecting the C6v symmetry, Dirac dispersions open a gap and massive chiral quasiparticle appears as eigenmode carrying specific pseudospin defined in the hexagonal unit cell. We have demonstrated that the massive chiral quasiparticle can be exploited for realizing topological states. As an explicit example, we show the creation of topological photonic crystal based on dielectrics, and its applications to brand-new topological photonic integrated circuits (TPICs) and topological cavity surface emitting laser (TCSEL).
The NIMS Award 2021 was given to three distinguished scientists who have achieved outstanding results in the field of “research on quantum materials.” The award-winning lectures will be streamed online.