Emergent phases from the interplay between correlation and disorder: non-Fermi-liquid type Weyl metals and quantum critical metals with finite randomness
The interplay between correlation and disorder has been one of the most important and hardest problems in strongly correlated systems. In this talk, I will view their interplay as a rich source for new interesting phases. In the first half, I will talk about the possibility of universal appearance of Weyl fermions in magnetic-doped semiconductors . Tuned to magnetic quantum criticality, the system follows the universal scaling law governed by magnetic critical fluctuations. A non-trivial aspect here is that an electron ’ s band gap parameter acquires a “ screening ” effect from such critical fluctuations. This novel scaling behavior opens up the possibility that the band gap of semiconductors, which is usually too large to be closed by the Zeeman splitting, can be closed by applying magnetic fields to give rise to a pair of Weyl nodes. The resulting Weyl metallic phase is distinguished from ordinary ones in that Weyl fermions are strongly coupled with critical fluctuations and lose their coherence completely in the low-energy limit. In the second half, I will talk about quantum critical metals with finite randomness emerging in two-dimensional nematic quantum criticality in the presence of nonmagnetic disorder . It turns out that the interplay between long-range correlation and elastic disorder scattering is an essential ingredient for understanding transport properties in such quantum critical metals. To understand their interplay, we start from a clean quantum critical point to take nematic critical fluctuations first and elastic disorder scattering further. Interestingly, nematic critical fluctuations suppress all inter-patch disorder scattering channels except forward scattering channel. The resulting local-patch theory has a stable fixed point whose scaling law is determined not only by the fermion-critical mode coupling but also by the forward scattering amplitude. This research would be the first step in understanding the T-linear electrical resistivity as a characteristic feature of non-Fermi liquids.
 Emergence of non-Fermi-liquid type Weyl metals driven by doped magnetic impurities in spin-orbit coupled semiconductors, Kyoung-Min Kim, Jinsu Kim, Soo-Whan Kim, Myung-Hwa Jung, and Ki-Seok Kim, Phys. Rev. B 98, 205133, (2018).
 Protection of effective hydrodynamics from Anderson localization in two dimensional nematic quantum criticality, Kyoung-Min Kim, Ki-Seok Kim, arXiv:1905.08442, (2019).
Host: Prof. Bohm Jung Yang