Wang group

• Dr. Shuqiu Wang

  Lecturer

Research Interests & Activities

My research group focuses on visualizing novel quantum states in strongly correlated electron systems. My group study topological and unconventional superconductors through advanced scanning tunnelling microscopy (STM) techniques developed in our laboratory. We implement beyond state-of-the-art experimental approaches to investigate quantum criticality and exotic electronic phenomena in materials such as heavy fermion compounds and high-temperature superconductors. Our work reveals the atomic-scale properties of these quantum materials, providing insights into pair density waves, orbital ordering, and topological surface states. Much of our research examines the interplay between superconductivity and other electronic orders, with recent breakthroughs in visualizing p-wave topological superconductivity in UTe₂ and orbital ordering in cuprates.

Topological superconductivity

The properties of superconducting materials, their perfectly dissipationless electronics, perfect diamagnetism, and macroscopic quantum mechanical dynamics are all the products of the formation of a macroscopic quantum fluid of electron pairs. To better understand this, we have developed the first scanned Josephson/Andreev tunnelling microscopes (SJTM/SATM) which provide direct access to the topological surface states.

Although nodal spin-triplet topological superconductivity appears probable in UTe₂, its superconductive order parameter has not yet been established. If spin-triplet, it should have odd parity so that . A distinctive identifier of such nodal spin-triplet superconductors is the appearance of an Andreev bound state (ABS) on surfaces parallel to a nodal axis, in the form of a topological quasiparticle surface band (QSB). Moreover, theory shows that specific QSB characteristics observable in tunnelling to an s-wave superconductor distinguish between chiral and non-chiral  order parameters. To search for such phenomena in UTe₂, we employ s-wave superconductive STM scan-tip imaging and discover a distinct TSB signature, an intense zero-energy Andreev conductance maximum at the (0-11) crystal termination. Its imaging yields zero-energy quasiparticle scattering interference evidence for two nodes aligned with the crystal a-axis. Development of the zero-energy Andreev conductance peak into two finite-energy particle-hole symmetric conductance maxima as the tunnel barrier is reduced, then signifies that UTe₂ superconductivity is non chiral. Ultimately, these data imply that the superconductive is the odd-parity non-chiral B_3u state.

Electron pair density wave state

Superconductors are materials that exhibit zero electrical resistance when cooled to temperatures of just a few kelvin. But harnessing this remarkable property for practical applications — in energy transmission and electronics, for example — requires materials that superconduct at higher temperatures. And to induce such behaviour, it must first be understood. A particular class of new superconductor has shown an intriguing phenomenon that involves a periodic modulation of electron density, known as a pair density wave. We have visualised the pair density waves in d-wave and p-wave unconventional superconductors.

Current researchers and PhD students