Qimiao Si
Professor
Harry C. and Olga K. Wiess Professor of Physics and Astronomy
Email: qmsi@rice.edu
- B.S., University of Science and Technology of China, 1986
- Ph.D., University of Chicago, 1991
- Alfred P. Sloan Research Fellow
- Humboldt Research Prize
- Fellow, Institute of Physics (U.K.)
- Fellow, AAAS (American Association for the Advancement of Science)
- Fellow, American Physical Society
- Ulam Distinguished Scholar, Los Alamos National Laboratory
- Vannevar Bush Faculty Fellow
- Phone: 713-348-5204; Fax: 713-348-4150
Primary Department
Department of Physics and Astronomy
Department Affiliations
- Department of Physics and Astronomy
- Smalley-Curl Institute
- Wiess School of Natural Sciences
Websites
- Rice Center for Quantum Materials
- Condensed Matter Physics @ Rice University
- Recent publications – search arxiv.org
Research Areas
Theoretical Condensed matter physics, specializing in strongly correlated electron systems: quantum criticality and emergent phases, iron-based high temperature superconductivity, topological metals driven by strong correlations.
Research Profile
Qimiao Si is the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice University. He obtained his B.S. degree from the University of Science and Technology of China and Ph.D. degree from the University of Chicago. He did postdoctoral works at Rutgers University and University of Illinois at Urbana-Champaign. He has been on the faculty of Rice University since 1995.
Prof. Si works in the field of theoretical condensed matter physics. His major contributions have been in the area of strongly correlated electron systems, including quantum criticality and emergent quantum phases, magnetic heavy fermion metals, high temperature iron-based superconductivity, topological metals driven by strong correlations, and mesoscopic and disordered electronic systems.
He is particularly well known for his contributions to the theory of quantum criticality, which concerns the physics of matter undergoing a transition from one quantum state to another. He introduced and developed the theory of local quantum criticality, which involves the notion of critical destruction of Kondo entanglement. The theory goes beyond the textbook Landau framework, and has received extensive support by experiments in magnetic heavy fermion systems. He has made seminal contributions to the field of iron-based superconductors, contributing broadly to the understanding of electron correlations, quantum criticality, magnetism, nematicity and superconductivity. In the area of topological states driven by strong correlations, he pioneered a Weyl-Kondo semimetal state. He has introduced the Bose-Fermi Kondo model and the method of the extended dynamical mean field theory, and contributed to the early development of the dynamical mean field theory. Other topics he has studied include the spin dynamics of the high temperature cuprate superconductors, metal-insulator transition in disordered and interacting electrons in two dimensions, experimental signatures of spin-charge separation, non-Fermi liquid states in an extended Hubbard model and in quantum impurity systems, and Mott transition between metallic and correlated insulating phases of interacting electrons.
Prof. Si was named a Sloan Research Fellow in 1996, and received a Cottrell Scholar Award from the Research Corporation for Science Advancement in 1998. He was elected a Fellow of the British Institute of Physics in 2004, the American Physical Society in 2005, and the American Association for the Advancement of Science in 2008. He received a Humboldt Prize from the Alexander von Humboldt Foundation in 2012, and was chosen as a Ulam Distinguished Scholar by the Center for Nonlinear Studies of Los Alamos National Laboratory in 2018. In 2023, he was named a Vannevar Bush Faculty Fellow.
As of December 2020, he has published over 215 scientific articles (including 32 in Science, Nature, their Group Journals and PNAS, and 50 in Physical Review Letters) and has given more than 370 invited talks (including over 200 at conferences) on his research. He has been serving as a General Member on the Board of the Aspen Center for Physics (since 2009), was a Member of the Advisory Editorial Board of Journal of Physics – Condensed Matter (2002-2006), and has chaired or co-organized many international conferences, workshops or programs, including the 2007 International Conference on Strongly Correlated Electron Systems (SCES’07), the 2014 KITP Program on Magnetism, Bad Metals and Superconductivity — Iron Pnictides and Beyond, and the 2018 Aspen Winter Conference on High Temperature Superconductivity — Unifying Themes in Diverse Materials.
Research Statement
Qimiao Si works in theoretical condensed matter physics, with an emphasis on topics in strongly correlated electron systems including quantum criticality, unconventional superconductivity, and correlated electronic topology.
Strongly correlated electron systems are at the forefront of condensed matter physics. Their theoretical description is a challenge that provides rich opportunities for creative and original research. The fundamental question is how the electrons are organized and, in particular, whether there are principles that are universal among the various classes of these strongly correlated materials. The overarching goal of the group’s research is to seek such principles of universality. Along the way, it is also fascinating to explore the diversity of the phenomena that result from electron correlations.
One area of Prof. Si’s current interest is quantum criticality. He and his collaborators have advanced a by now well-known theory of local quantum criticality. Developed in the context of magnetic heavy fermion metals, which is a prototype system for quantum phase transitions, this theory features the “beyond-Landau” physics of critical Kondo destruction. The notion that electronic excitations undergoing a localization-delocalization transition drive quantum criticality has impacted the developments in wider contexts, in high-temperature superconductors and beyond. A related topic of his recent research addresses novel phases that emerge in the vicinity of quantum critical points; for heavy fermion systems, his work here appears in the form of a global phase diagram. He has also been interested in quantum critical physics in a variety of other contexts.
Another focus of Prof. Si’s ongoing research concerns iron-based superconductors. From the very beginning of the field, he recognized that the bad metallicity of these systems implies that strong correlations play an important role. This line of consideration has opened up studies on orbital-selective Mott phenomena. A corollary of this approach is that magnetism is primarily driven by short-range and frustrating (J1-J2) interactions, a notion that he and his collaborators have pioneered. This approach has led them to theoretically predict a magnetic quantum critical point in iso-electronically tuned iron pnictides, which has been verified by extensive subsequent experiments. His recent work has also explored the related magnetic frustration physics in the iron chalcogenides, including its effect on the nematicity in FeSe. Finally, he has been studying the implications of such magnetic interactions for the unconventional superconductivity. He and his collaborators introduced the notion of orbital-selective superconducting pairing. Recent work along this direction has shown how high Tc superconductivity may develop in the iron chalcogenides with seemingly unfavorable Fermi-surface conditions, and how the orbital selectivity gives rise to a new superconducting pairing state.
Yet another direction is on topological metals driven by strong correlations. His group has recently advanced the Kondo-driven Weyl semimetal state. Contemporaneous experiments in heavy fermion semimetals have provided thermodynamic and transfport evidence for this Weyl-Kondo semimetal. Both the theory and the strategy used in establishing the Weyl-Kondo semimetal state promise to open up a new general design principle for strongly correlated topological states.
A variety of other topics on correlated electron systems are also of interest to the group. These range from non-Fermi liquid behavior, cuprate superconductors, quantum entanglement in many-body systems, disordered and interacting electronic systems, metal-insulator transitions, out of equilibrium behavior of electronic systems, spin transport, and the probe of spin-charge separation.