The Mao group’s research interests lie in synthesis and study of quantum materials, including topological Dirac and Weyl semimetals, 2D magnetic topological materials, high entropy materials, strongly correlated oxides, novel superconductors, and nonlinear optical materials. Our group not only grows bulk single crystals of various quantum materials, but also performs various measurements to study the physics of quantum materials. For crystal growth, we primarily use the optical floating-zone, flux, chemical vapor transport, and Bridgman methods. Besides material synthesis, we also perform electronic transport, magnetization, and specific heat measurements to characterize and understand electronic, magnetic, and thermodynamic properties of quantum materials. Our group also performs high-field measurements at the National High Magnetic Field Laboratory to seek new quantum phenomena under high magnetic fields. Furthermore, Dr. Mao has also established extensive collaborations with researchers at other institutions and National Laboratories to study quantum materials using other techniques such as neutron scattering and photoemission spectroscopy.
Our recent research activities are more focused on topological materials, including topological insulators and Dirac and Weyl semimetals. These new classes of quantum materials all feature relativistic fermions with linear energy dispersion that can be described by the Dirac or Weyl equations. The unique topological properties of the electronic band structures in topological materials result in distinct transport properties such as high carrier mobility and large magnetoresistance. These materials also provide access to fascinating exotic quantum states of technological relevance such as the quantum anomalous Hall insulator which can support dissipationless current. As such, topological materials hold great promise for applications in information technology. The objective of our research in this area is to discover novel topological materials and understand their exotic quantum phenomena through bulk single crystal growth, magnetotransport, and quantum oscillation measurements.
In addition to topological materials, we are also developing several other avenues of research which aim to discover novel nonlinear optical materials, novel superconductors, and 2D magnetic materials with non-centrosymmetric/chiral structures. Research on catalytical and high-entropy materials is also being developed through collaborations with other professors in Materials Science and Engineering and Chemistry Departments.
Recent accomplishments of his research group include demonstrations of a long-sought ideal time reversal symmetry breaking type-II Weyl semimetal (Physical Review X 2021), spin-valley locking and three-dimensional quantum Hall effect in a non-centrosymmetric Dirac semimetal BaMnSb2 (Nature Communications 2021), a ferromagnetic Weyl semimetal Co2MnAl (Nature Communications, 2020), noncollinear spin structure-induced intrinsic anomalous Hall effect in antiferromagnetic topological insulator MnBi2Te4 [Phys. Rev. Research 1, 012011(R) (2019)], unusual interlayer quantum transport behavior caused by the zeroth Landau level in a Weyl semimetal YbMnBi2 [Nature Communications 8, 646 (2017)], topological nodal-line fermions in ZrSiSe and ZrSiTe [Phys. Rev. Lett. 117, 016602 (2016)], as well as discovery of a magnetic topological semimetal Sr1-yMn1-zSb2 [Nature Materials 16, 905 (2017)].