title: Observation of an exceptional point in a two-dimensional ultrasonic cavity of concentric circular shells.
abstract: We report observation of an exceptional point in circular shell ultrasonic cavities in both theory and experiment. In our theoretical analysis we first observe two interacting mode groups, fluid- and solid-based modes, in the acoustic cavities and then show the existence of an EP of these mode groups exhibiting a branch-point topological structure of eigenfrequencies around the EP. We then confirm the mode patterns as well as eigenfrequency structure around the EP in experiments employing the schlieren method, thereby demonstrating utility of ultrasound cavities as experimental platform for investigating non-Hermitian physics.
authors.affiliation: School of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul 151-742, Korea.
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Shin
authors.affiliation: School of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul 151-742, Korea.|Samsung Electronics Company, Hwaseong 445-330, Korea.
authors.forename: Hojeong
authors.initials: H
authors.lastname: Kwak
authors.affiliation: School of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul 151-742, Korea.
authors.forename: Songky
authors.initials: S
authors.lastname: Moon
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.
authors.forename: Sang-Bum
authors.initials: SB
authors.lastname: Lee
authors.affiliation: Russia Science Seoul, Korea Electrotechnology Research Institute, Seoul 121-912, Korea.
authors.forename: Juhee
authors.initials: J
authors.lastname: Yang
authors.affiliation: School of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul 151-742, Korea.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: An