Why do electrons and atoms in a solid state material spontaneously arrange themselves in patterns, and how does this relate to tunable electrical conduction?

#Spontaneous symmetry breaking #Beyond Born-Oppenheimer approximation #Metal-to-insulator transitions

Left: energy-momentum dependent spectral function along the Ta-chain direction in Ta2NiSe5

How can low dimensionality make materials switch between a metal, an insulator and a superconductor? Where does the energy go during these transitions? (How) can we make the system Tc higher? How do correlated orders interact with each other and (how) can we manipulate these orders?

#Quantum fluctuations #Superconducting phase coherence #Electron-phonon coupling #Orbital content engineering

Left: energy-momentum dependent spectral function along the Cu-Cu direction in Bi2Sr2CaCu2O8

How can the electronic properties of itinerant magnets be used to create high temperature magnetic materials in two-dimensions for real world spintronic applications?

#Local moment #Itinerant magnetism #Magnetoelastic coupling

Left: Fermi-surface measured within the van der Waals plane of Ni-doped Fe5GeTe2

Isoelectronic molecules often share similar chemical properties - can lab-designed solids be used to simulate the quantum properties in their isoelectronic and/or isostructural siblings?

#Supramolecular self-assembly #Artificial lattice #Quantum simulation

Left: our newly commissioned portable organic molecular beam epitaxy system for versatile molecular self assembly. Inset: molecular beam epitaxy grown naphthalocyanine (H2Pc) monolayer of which structure mimics a 2D square lattice system and which may modify the electronic structure of the substrate.

Traditional approach to conduct temperature dependent studies in ARPES involves global warm-cool cycles of the entire (massive) cryostat. This process is not only time-consuming and energy-inefficient, but more damagingly causes outgassing that is often detrimental to the fresh sample surface under active investigation. As shown to the left, a high-power CW laser is employed to achieve localized sample heating and create graduated thermal profiles on the sample surface. It will also be used to flash clean the surfaces of ex-situ prepared heterostructure devices and patterned structures. Moreover, it will be used to modify surface adsorbate density during and after targeted gas molecule or alkaline metal deposition. Last but not least, it can also maintain a steady state exciton population.

Integration of nano-photonics design with traditional ARPES substrate also offers another route towards more extreme sample environment, and will also path the way to a generic, compact, low cost, and highly controllable on-demand property tuning as well as the creation of new phases. We are working with Prof. Owen Miller and Prof. Peter Rakich's groups to explore this exciting avenue.

• sub-resolution superconducting energy gap extraction

• automatic spectral feature extraction with image-based learning

• condensation energy analysis

• 4D X-Y-E-kp spectral information extraction (symmetry, mosaicity, intensity)

• detector grid removal and distortion correction