Next generation of scientist

One of my life long projects is to produce next generation of scientists. I mean real scientists, not just people working in field of scientific research. The key to this project is to systematically raise the level of creativity: the ability to envision what has not been seen, to produce what has not been made, to open doors to the unknown world. In order to achieve the goal, we will be using modern thinking techniques in every aspect of our daily research activities.

High Temperature Superconductivity

In many senses, a superconductor is a giant atom with one single wavefunction to describe the entire macroscopic entity. For that reason, superconductivity is a bridge between the microscopic world described by quantum physics and the macroscopic world that we live in. Another example of such bridge is the black hole. Just as black hole, superconductivity is not well understood even after more than 100 years of discovery. To fully understand the mystery of superconductivity represents a challenge to the human intelligence. One way to attack this problem is to discover new families of superconductors with high temperatures so that we can find common features that are crucial to this fascinating phenomenon.

We invited you to join us to solve this pattern problem. The reward is a so called Nobel prize.

Topological Superconductivity

A subset of superconductors also have nontrivial topological properties. Such topological superconductors are expected to host exotic Majorana fermion excitations on their surface with unusual quantum statistics. This property makes Majorana fermions the most promising building block for quantum calculations without decoherence. On the other hand, the number of topological superconducting materials can still be counted on one hand, and the existence of theoretically predicted Majorana fermions on the surface state of topological superconductors has not been unambiguously demonstrated. We have recently discovered a candidate of topological superconductor, UTe2, that has attracted enormous interest in the research community. We are now working towards a topological qubit:

  • Discovery more topological superconductors
  • Demonstrate clear signature of surface Majorana fermions
  • Realize quantum braiding of Majorana fermions and therefore topological qubits

Left: discovery of spin triplet superconductivity in UTe2. Right: STM study reveals evidence for chiral surface states.

Strongly correlated topological systems

Topological revolution in the condensed matter physics has greatly broadened our horizon. However, the effect of strong correlation, another important thread in condensed matter physics giving rise to a plethora of exciting phenomena, on the band structure topology is not well understood, due to the theoretical challenge to deal with the interplay between Coulomb repulsion and kinetic degrees of freedom for the electrons. It is conceivable that when strong correlation and band structure topology are combined, the low-energy electronic excitations of topological phases of matter will involve spin, charge, orbital and lattice degrees of freedom, giving rising to yet-unknown phases, transitions, and functionalities that may hold promise for the new generation of electronic devices. We have recently observed some interesting phenomena due to the interplay of Kondo physics and band structure topology, demonstrating the rich physics yet to be explored in the new territory. One example is the anomalous Hall effect up to room temperature in not magnetically ordered Kondo system.

We observed anomalous Hall effect up to room temperature in not magnetically ordered Kondo systems.

Quantum Spin Liquid

Quantum spin liquid is another highly unusual quantum state. It was (no longer) believed to have relation with high temperature superconductors. New theory and experiments show that certain quantum spin liquid can also host Majorana fermions and therefore are also promising candidate for building topological quantum computers.

Two Dimensional Materials

Atomically thin van der Waals materials provide extremely versatile platforms for exotic quantum phenomena and new electronic device architectures. Presently, such 2D materials exhibit a vast range of properties, which includes magnetism and superconductivity. One can easily stack different layers with different properties to achieve new phenomena, like Legos. It is conceivable that there are more exotic properties to be discovered. Recently, we have discovered 2D magnetic material with a previously unknown structure.