Research
Our current research focuses on the following general directions:
- Strongly correlated and quantum confined electronic systems, including competing orders in
superconducting and magnetic perovskite oxides, pairing mechanism and pseudogap phenomena of cuprate
superconductors, quasiparticle excitations and pairing symmetry of FeAs- and FeSe-based superconductors, atomically resolved electronic properties of graphene, graphene-based atomic switches, strain-induced pseudo-magnetic fields and fractional/integer quantum Hall effects on graphene, strain-induced novel electronic states of silicon nano-pillars, ferromagnetic metal (FM)-filled carbon nanotubes, and topological insulators.
- 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
- 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
Our primary research activities in the past few years have concentrated on the
following areas:
- Superconductivity:
- competing orders, pseudogap phenomena and pairing mechanism of cuprate superconductivity
- magnetic field-induced microscopic orders and quantum fluctuations in cuprate superconductors
- pairing symmetry and low-energy quasiparticle excitations in iron-pnictide 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
- Magnetism:
- physical origin and systematic control of the colossal magnetoresistive (CMR)
effect in perovskite manganites
- discovery and investigation of giant spontaneous Hall effect in perovskite cobaltites
- 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
- Nano-electronics:
- strain-induced giant pseudo-magnetic fields and charging effects on graphene in nano-scales.
- atomically resolved electronic density of states of graphene and graphene-based nano-electronic devices as a function of temperature and magnetic fields.
- local electronic states of FM-filled carbon nanotubes and related nano-scale devices.
- surface electronic states of topological insulators.
- novel electronic properties of strained silicon nano-pillars at the nano and atomic scales. (In collaboration with Professor Axel Scherer).
- Spintronics:
- Fabrication of heterostructures of organic semiconductors and ferromagnetic manganites (OSE/FM) using
a pulsed laser deposition (PLD) system and an evaporation chamber
- Investigation of the spin and charge quantum transport in the OSE/FM heterostructures using a
spin-polarized STM/NSOM
- Optimization of the OSE/FM heterostructures for best tunneling magnetoresistance and electroluminescence
- Development of soft lithographic techniques for making spintronic & optoelectronic devices based on optimized FM/OSE/FM heterostructures
- Engineering crossed FM-filled carbon nanotubes for nano-scale spintronic devices