Theory

Currently, our center has 3 theory teams as introduced below.
             
Correlated Quantum Matter Theory                  

   Our research team studies a broad class of theoretical problems about correlated quantum matter by using the theoretical tools of analytic quantum field theory and numerical methods. Currently, we are focusing on new emergent quantum physics originating from the nontrivial interplay between electron correlations and bulk topological properties such as quantum critical phenomena in topological media, interacting Weyl/Dirac semimetals, 5d transition metal oxides, frustrated quantum magnets, etc. Our aim is to search for unconventional quantum states of matter beyond the conventional paradigms and theoretically design novel functional materials.

Selected Publications

  • B. -J. Yang, M. S. Bahramy, R. Arita, H. Isobe, E. ?G. Moon and N. Nagaosa, ?Theory of topological quantum phase transitions in 3D non-centrosymmetric systems?, Phys. Rev. Lett., 110, 086402 (2013).
  • B. -J. Yang, Mohammad Saeed Bahramy, and Naoto Nagaosa, ?Topological protection of bound states against the hybridization?, Nature Communications, 4, 1524 (2013).
  • B. -J. Yang and Naoto Nagaosa, ?Emergent topological phenomena in thin films of pyrochlore iridates?, Phys. Rev. Lett., 112, 246402 (2014).
  • B. -J. Yang, Eun-Gook Moon, Hiroki Isobe, and Naoto Nagaosa, ?Quantum criticality of topological phase transitions in 3D interacting electron systems?, Nature Physics 10, 774 (2014).
  • B. -J. Yang and Naoto Nagaosa, ?Classification of stable three-dimensional Dirac semimetals with nontrivial topology?, Nature Communications 5, 4898 (2014).
  • K. Ueda, J. Fujioka, B.-J. Yang, J. Shiogai, A. Tsukazaki, S. Nakamura, S. Awaji, N. Nagaosa, and Y. Tokura, ?Magnetic-field-induced insulator-semimetal transition in a pyrochlore Nd2Ir2O7 ?, Phys. Rev. Lett., 115, 056402 (2015).


Topological Matter Theory

   The Topological Matter Theory Group, led by IBS Young Scientist Dr Suk Bum Chung, is the junior theory groups established within the IBS Center for Correlated Electron Systems. We focus on theoretical studies topological phases of matter, such as topological insulator, topological superconductor and fractional quantum Hall state, occurring in correlated electron systems including transition metal oxide materials. We are also interested in unconventional superconductivity and Rashba spin-orbit coupling in interface and surface of various heterostructure.  
   Our method mainly focuses on studying exactly solvable models and field theory and hence is complementary to the first principle calculations. We seek to provide direction for experimental efforts in CCES as well as trying to understand the new experimental results. In addition, we seek collaboration with other related fields, such as quantum fluid and ultracold atoms.
  Since March 2015, Dr Jae-Seung Jeong and Dr Kihoon Lee have joined the group as the postdoctoral research fellows.

Selected Publications

  • Minsung Kim, Jisoon Ihm and Suk Bum Chung, Enhanced Rashba-Dresselhaus spin-orbit interaction near the band saddle point in 5d transition metal oxide heterostructure (in preparation).
  • Suk Bum Chung, Cheung Chan and Hong Yao, Dislocation Majorana zero modes in perovskite oxide 2DEG, arXiv:1505.00790
  • YeJe Park, Suk Bum Chung and Joseph Maciejko, Surface Majorana fermions and bulk collective modes in superuid 3He-B, Phys. Rev. B 91, 054507 (2015)
  • Suk Bum Chung, Joshua Horowitz, and Xiao-Liang Qi, Time-reversal anomaly and Josephson eect in time-reversal invariant topological superconductors, Phys. Rev. B 88, 214514 (2013)
  • Daesu Lee, Sang Mo Yang, Jong-Gul Yoon, and Tae Won Noh, Flexoelectric Rectification of Charge Transport in Strain-Graded Dielectrics, Nano Letters 12, 6436 (2012).
  • Suk Bum Chung, Srinivas Raghu, Aharon Kapitulnik and Steven A. Kivelson, Charge and spin collective modes in a quasi-1D model of Sr2RuO4, Phys. Rev. B 86, 064525 (2012).


First-principles Theory


   Our team, led by Dr. Choong Hyun Kim is the first-principles theory team to be established within the IBS Center for Correlated Electron Systems. A key element of our team is the prediction of new phases arise at the oxide interfaces from first-principles. And the project will be conducted in close collaboration with experimental group.
   The purposes of our team's project are to develop a first-principle based method for correlated transition metal oxides and to understand and discover novel physical properties of correlated oxides and related systems, such as magnetism, metal-insulator transition, superconductivity. It is expected that predictions based on our calculations will suggest new experiments where exotic states of matter may be found.

Selected Publications
  • Y. F. Nie, P. D. C. King, C. H. Kim, M. Uchida, H. I. Wei, B. D. Faeth, J. P. Ruf, J. P. C. Ruff, L. Xie, X. Pan, C. J. Fennie, D. G. Schlom, and K. M. Shen, Interplay of spin-orbit interactions, dimensionality, and octahedral rotations in semimetallic SrIrO3, Phys. Rev. Lett. 114, 016401 (2015).
  • Ho-Hyun Nahm and Yong-Sung Kim, Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4, NPG Asia Materials 6, e143 (2014).
  • Jin-Hong Park, Choong H. Kim, Hyun-Woo Lee, and Jung Hoon Han, Orbital chirality and Rashba interaction in magnetic bands, Phys. Rev. B 87, 041301(R) (2013).
  • hoong H. Kim, Heung Sik Kim, Hogyun Jeong, Hosub Jin and Jaejun Yu, Topological quantum phase transition in transition metal oxide Na2IrO3, Phys. Rev. Lett. 108, 106401 (2012).