Carbon nanocomposites refer to a class of material produced by embedding a low-dimensional carbon material (take for example 1D carbon nanotubes or 2D graphene) into a matrix of either polymer, ceramic, or metal. CNT and graphene are known to have an excellent electrical conductivity and their surfaces can be functionalized as well. This makes them suitable for a wide range of applications from sensing to wound dressing!. Over the past few years in collaboration with Korea Institute of Materials Science (KIMS), we have been developing piezo-resistive sensors based on CNT nanocomposites for motion detection as well as volatile organic compounds (VOC) sensor.
See our recent paper here to learn more about the subject.
In most cases, a nuclear spin in a host material is dormant and does not influence electron transport. However in a certain case particularly in a semiconductor material with s-wave conduction band like in GaAs, the hyperfine interaction can be significantly large and the interaction between an electron and a nuclear spin degree of freedoms cannot be ignored. In fact, if all nuclear spins were fully polarized in GaAs, the magnetic field (known as Overhauser or Hyperfine field) exerted on an electron spin would be as high as -5.3 T!. Likewise, a net of electron spin polarization would generate an effective magnetic field for the nuclear spin (known as Knight field) and shift the nuclear Zeeman energy level. One can directly measure electron spin polarization by looking at the shift in the electrically-detected nuclear magnetic resonance. Furthermore, measuring how fast the nuclear spin relaxes toward thermal equilibrium provides a way to probe electron spin fluctuations. One can study a great deal of electronic states in semiconductor nanostructures by measuring the Knight shift and the nuclear spin relaxation rate.
In collaboration with Prof. Yoshiro Hirayama and Assistant Prof. Katsushi Hashimoto of Tohoku University, we are actively exploring the topic to study various spin phase transitions in fractional quantum Hall states and anomalous conductance plateau observed below the lowest subband in a quantum point contact.
See our recent review on arXiv to learn more about the subject.
A spin system in nitrogen vacancy center (NV center) contained in nano-diamond is actively being exploited for quantum sensing. Among several existing electronic states in NV center, the spin of a negatively charge NV center (NV−) can be optically initialized by green laser and read out its red fluorescence, while its spin state can be manipulated by radio frequency magnetic fields. All the operations can be conveniently done at room temperature. NV− center is able to sense many physical quantities with superior sensitivity including magnetic field and electric field quantifications, temperature, mechanical vibration, as well as pH level. Furthermore, nanodiamond is known to have extraordinary photo-stability and high bio-compability. We are interested in using those excellent modalities for bio-marker applications including cell labelling, imaging, and sensing.
The project, started in FY 2021, is carried out in collaboration with Dr. Yulianti Herbani (Laser group), Dr. Yusuf Nur Wijayanto and Ken Paramayuda, M.Phil. (Microwave, acoustic, and photonics group), and Dr. Ahmad Randy (Analytical chemistry group).