Identification of exotic carriers in highly entangled Mott insulators

Eun-Gook Moon (Department of Physics, KAIST, e.g.moon@kaist.ac.kr)

Mott insulators may host highly entangled quantum many-body states, including quantum spin liquids. In this talk. we show that topological phase transitions may be utilized to identify Kitaev quantum spin liquids by tuning electric and magnetic fields [1-5]. We show that specific directions of magnetic fields may give gapless Majorana fermion excitations, constrained by the lattice symmetry. Furthermore, we also consider electric field effects and find that topological phase transitions may be controlled in sharp contrast to the common belief that an insulator is inert under weak electric fields due to charge energy gaps. We predict distinctive experimental signatures to detect Kitaev quantum spin liquids, especially in connection with candidate materials such as α-RuCl3. If time permits, we also discuss the recent results in TbInO3 where exotic charge carriers were identified by tera-hertz optical conductivity [6].

[1] Vestiges of Topological Phase Transitions in Kitaev Quantum Spin Liquids, Physical Review Letters 122, 147203 (2019)
[2] Identification of a Kitaev quantum spin liquid by magnetic field angle dependence, Nature Communications 13, 323 (2022)
[3] Thermodynamic evidence for a field-angle-dependent Majorana gap in a Kitaev spin liquid, Nature Physics 18, 429 (2022)
[4] Majorana-fermion origin of the planar thermal Hall effect in the Kitaev magnet RuCl3, arXiv:2305.10619
[5] Manipulating topological quantum phase transitions of Kitaev’s quantum spin liquids with electric fields, arXiv:2308.00760
[6] Unconventional room-temperature carriers in the triangular-lattice Mott insulator TbInO3, Nature Physics (2023, online).

About the Speaker

Eun-Gook received his B.S in physics at Seoul National University in 2005 and received his Ph. D. in Physics from Harvard University in 2011. He was a postdoctoral Fellow in Physics at University of California, Santa Barbara during 2011-2014. He was a Kadanoff Fellow in Physics at University of Chicago during 2014-2015. Then, he joined in Department of Physics at Korea Advanced Institute of Science and Technology (KAIST) as a faculty member since 2015.

The focus of Eun-Gook’s research is the theoretical investigation of quantum many-body systems, particularly, quantum spin liquids and topological phases of matter in strongly correlated systems as well as cold atomic and molecular systems in quantum simulations.

Eun-Gook is a member of the Young Korean Academy of Science and Technology and the principal investigator of the Ultra Quantum Materials basic research group funded by the Korean National Research Foundation. He also received numerous honors and awards including the Academic Prize (2020) from KAIST.