SEMINAR 1 Title Charge Frustration and Electron pairing

SEMINAR 1. Title : Charge Frustration and Electron pairing in a Triangular Triple Quantum Dot 2. Speaker : Yunchul Chung (Department of Physics , Pusan National University) 3. Time : 16: 00 – 17: 00, Thursday, March 02, 2017 4. Place : e+ Lecture Hall (room 83188), 2 nd Research Building, Sungkyunkwan University 5. Summary : Exotic states such as charge frustrated state and electron pair state have been simulated in artificial lattice formed with coupled quantum dots. First, the charge (isospin) frustration induced by a geometrical symmetry in a triangular triple quantum dot is realized. We observe the ground-state charge configurations of six-fold degeneracy, the manifestation of the frustration. The frustration results in omnidirectional charge transport, and it is accompanied by nearby nontrivial triple degenerate states in the charge stability diagram. The work demonstrates a unique way of studying geometrical frustration in a controllable way. Second, the electron pairing due to repulsive Coulomb interaction in a triple quantum dot (TQD) is experimentally studied. It is found that electron pairing in two dots of the TQD is mediated by the third dot, when the third dot strongly couples with the other two via Coulomb repulsion so that the TQD is in the two-fold degenerate ground states of (1, 0, 0) and (0, 1, 1) charge configurations. Using the transport spectroscopy that monitors electron transport through each individual dot of the TQD, we analyze how to achieve the degeneracy in experiments, how the degeneracy is related to the electron pairing, and the resulting nontrivial behavior of electron transport. Our findings may be exploited to design and synthesize materials or chemicals with nontrivial electron correlations and functionalities. 6 Background : • Education Ph. D : 1990 -1995, Physics, Korea University M. S. : 1988 -1990, Physics, Korea University B. S. : 1984 -1988, Physics, Korea University • Work Post-Doctoral Research Associate, Oxford University, 1996 -2000 Visiting Scientist, Weizmann Institute of Science, 2000 -2003 Assistant Professor, Pusan National University, 2003 -2008 Associate Professor, Pusan National University, 2008 -2014 Professor, Pusan National University, 2005 -present 7. Questions : (☏ 031 -299 -4115)