Overview
Our ongoing research is centered on the following overarching themes outlined in the subsequent list:
- Condensed matter experiments, focusing on scientific and technological topics of correlated electrons (e.g., high-temperature superconductors; colossal magnetic perovskites), topological materials (e.g., topological insulators and superconductors; topological states for quantum information), low-dimensional systems (e.g., van der Waals materials including graphene, h-BN and two-dimensional transition-metal dichalcogenides; graphene nanostripes; carbon nanotubes; nanoparticles; quantum dots), valleytronics, spintronics (based on spin-orbit-coupled materials, half-metallic ferromagnets), nanoscience and nanotechnology (e.g., instrumentation of scanning probe microscopy for nanoscale characterization; nanofabrication of electronic, optoelectronic, valleytronic and spintronic devices; nanoscale strain engineering of graphene and transition-metal dichalcogenides) and energy research (e.g., energy conversion in photovoltaic and fuel cells; supercapacitors and lithium ion batteries for energy storage).
- Nano-scale instrumentation with variable temperature capabilities for surface and subsurface characterizations of the electronic and mechanical properties of novel nanostructures, nano-assemblies and molecules
- Low-temperature high-field Scanning Tunneling Microscope (STM)
- Variable temperature STM/Scanning Electron Microscope (SEM)
- Low-temperature STM/Near-field Scanning Optical Microscope (NSOM)
- Organic/Magnetic Heterostructures for Spintronics & Optoelectronics
- Investigation of spin and charge quantum transport in the heterostructures using cryogenic STM/SNOM
- Optimizing the tunneling magnetoresistance and electroluminescence for spintronic and optoelectronic applications
- Studies of spin-polarized tunneling in FM-filled carbon nanotubes; exploration of possible spintronic devices based on FM-filled carbon nanotubes.
- Applications of Superconducting Cavity Stabilized Oscillators
- Precise measurements of the Bose-Einstein condensation of quantum gases and critical phenomena of quantum fluids
- High frequency stability microwave sources
Primary Research Activities
Within the aforementioned list, our current emphasis is on the following research areas:
Superconductivity
- competing orders, pseudogap phenomena, pairing symmetry and pairing mechanism of high-temperature superconducting cuprates
- magnetic field-induced microscopic orders and quantum fluctuations in cuprate superconductors
- competing orders, pairing symmetry, pairing mechanism and low-energy quasiparticle excitations in iron-based superconductors
- non-equilibrium superconductivity associated with excess charge and spin injection into the cuprate superconductors
- vortex phases and dynamics of high-temperature and conventional amorphous superconductors, from DC to radio to microwave frequencies
Topological Matter
- proximity-induced magnetism and superconductivity on topological insulators
- impurity resonances and topological defects in the surface state of topological insulators
- applications of magnetically doped topological insulators to spintronics and quantum information technology
Graphene and Graphene-based Devices
- low-temperature PECVD growth of high-quality large-area strain-free graphene
- nano-scale strain energineering of graphene for designer gauge potentials and novel nano-electronics
- development of graphene-based photovoltaic cells
Transition Metal Dichalcogenide (TMD)-based Optoelectronic Devices
- CVD growth of monolayer TMD
- Surface plasma polariton induced enhanced light-matter interactions
- strain engineering of TMD to control excitonic physics
Instrumentation
- a variable-temperature (from ~ 2 to 300 K) high-field-compatible scanning tunneling microscope (STM) and spin-polarized STM with both atomic-scale spatial resolution and large scanning area
- a variable-temperature (from ~ 8 to 300 K) ultra high vacuum (UHV) scanning tunneling microscope (STM) combined a scanning electtron microscope (SEM) for efficient placement, imaging and spectroscopic studies of nano-scale structures and nano-arrays
- a variable-temperature (from ~ 4 to 300 K) high-field-compatible UHV scanning tunneling microscope (STM) combined with a near-field scanning optical microscope (NSOM) for studies of tunneling magnetoresistance and electroluminescence of organic/magnetic heterostructures with nano-scale spatial resolution
- broadband apparatus for small-signal complex resistivity and magnetic susceptibility measurements
- superconducting cavity-stabilized oscillators (SCSO) integrated with the high-resolution thermometry for state-of-the-art frequency standards and for precise measurements of fundamental physical properties of quantum gases and fluids
- high-Q dielectric microwave resonators for cryogenic surface impedance measurements of materials in high magnetic fields and over a broad frequency range