Research

Cuprate Superconductivity

Due to the vast amount of theoretical and experimental work performed for 25 years and its relatively simple band structure, it is an ideal test bed for any newly developed and advanced spectroscopic technology. Still holding the title of the highest-Tc superconductor with undetermined pairing mechanism, it requires a more radical, extensive and conclusive measurement technique in real and momentum space and a revolutionary analytical framework. Its high Tc also requires a variable temperature SI-STM with unprecedentedly wide temperature range.

Iron-based Superconductivity

Due to its complicated band structure and magnetic iron-embedded host layers, the discovery of iron-based high-Tc superconductors have raised surprises and new challenges for physicists. Claims of experimental determination of the gap symmetry, which will be a prerequisite for determination of the pairing mechanism, are being reported by groups with ARPES or SI-STM with high magnetic field but the consensus is not reached yet. Some physicists think that the gap symmetry and the pairing mechanism may be qualitatively different for different variations of iron compound structures. The complicated band structure generally requires a high-magnetic-field SI-STM with higher momentum space resolution than reported to date.

Topological Insulators

Due to the strong spin-orbit coupling, the conducting surface states of these insulating materials have unique spin-momentum interlocking. The result is suppression of the back scattering from atomic scale defects. Understanding this intriguing phenomena may lead us to a new class of quantum electronic devices. SI-STM is naturally an ideal tool for investigating the backscattering of surface states off atomic terraces, surface disorders and magnetic impurities.

Graphene-derivatives

Graphene is a single-atom-thick carbon network with large carrier mobility and mechanical strength. The isospin degree of freedom due to the two equivalent atoms in the unit cell and the unique massless Dirac band structure induce interesting novel phenomena in high magnetic field and in bi-layer graphene structure directly observable by SI-STM. There is also a prediction that modulation-doped graphene shows interesting lensing effect for the conduction electrons which may lead to a new class of electron optics.

Low Dimensional Electron Systems

Due to the confinement effects, low dimensional electron systems such as nanotubes and graphene nano-ribbons show unique band structures and many-body phenomena. Also the internal space of nanotube can be filled with special molecules to show interesting effects in the nanotube band structure. Reliable SI-STM measurements on device structures made of these low dimensional electron systems require special technology yet to be developed.