Interests: Theoretical condensed matter physics of strongly correlated electron systems, classical and quantum phase transitions, unconventional superconductivity, quantum magnetism, quantum impurity models, low dimensional physics and cold atoms.

Overview: Heavy fermion metals are a type of rare-earth inter-metallic compound that have charge carriers which appear to be thousands of times heavier than a normal electron. The heavy charge carriers are due to a phenomenon known as the Kondo effect, which arises at low temperatures as a result of magnetic moments interacting with a sea of electrons. Interestingly, the competition between magnetism and the Kondo effect can give rise to a zero temperature quantum phase transition (QPT) where the Kondo effect is destroyed as a result of magnetic order. The critical destruction of the Kondo effect defies a description in terms of the conventional theory of phase transitions and therefore new theories need to be developed.   My graduate research focus is threefold and can be summarized as follows: quantum critical phenomena, frustrated magnetism and unconventional superconductivity.

Quantum Critical Phenomena: One area of my research has been developing a theoretical understanding of the nature of Kondo destroyed quantum critical points. Specifically, I have developed a continuous time quantum Monte Carlo approach to study the competition of the Kondo effect and magnetic order (J. Phys.: Conf. Ser. & PRB). In addition I have introduced the Binder cumulant to determine the location of Kondo destroyed quantum critical points. My collaborators and I have also shown that the relaxation rate of electrons in a heavy fermion metal is linear in temperature (PRL) with a single particle greens function and spin susceptibility that obey energy-over-temperature scaling at the quantum phase transition, consistent with experiments on the compound YbRh2Si2. In addition, we have shown that even in mixed valence heavy fermion metals it is possible to have a Kondo destroyed quantum critical point (PRL). As a consequence of the mixed valence nature we have shown charge excitations become critical at the quantum phase transition.  Figure reproduced from Phys. Rev. B, © 2013, The American Physical Society.

Frustrated Magnetism:
Recently a number of geometrically frustrated heavy fermion metals have been discovered. These compounds have a number of exciting possible ground states that arise due to magnetic frustration and Kondo screening (PRBR). In this aspect, my collaborators and I have been investigating the Kondo lattice model on the geometrically frustrated Shastry-Sutherland lattice (arXiv:1309.0581). We have found interesting new QPTs dictated by the degree of magnetic frustration in the system, our results have also made a step forward in developing a global phase diagram of heavy fermion metals.

Unconventional Superconductivity: The last area of my current research concerns unconventional superconductivity in heavy fermion metals.  We have introduced an effective model to study superconducting fluctuations at a Kondo destroyed QPT (arXiv:1308.0839). In one of our main conclusions, we have shown that pairing is enhanced in the vicinity of the QPT.