title: Manifestation of PT symmetry breaking in polarization space with terahertz metasurfaces.
abstract: By utilizing the vector nature of light as well as the inherent anisotropy of artificial meta-atoms, we investigate parity time symmetry breaking in polarization space using a metasurface with anisotropic absorption, whose building blocks consist of two orthogonally orientated meta-atoms with the same resonant frequency but different loss coefficients. By varying their coupling strength, we directly observe a phase transition in the eigenpolarization states of the system, across which the long axis of the eigenpolarization ellipses experience a sudden rotation of 45°. Despite the lack of rotational symmetry of the metasurface, precisely at the phase transition, known as the exceptional point, the eigenmodes coalesce into a single circularly polarized state. The PT symmetric metasurfaces are experimentally implemented at terahertz frequencies.
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Lawrence
authors.affiliation: School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
authors.forename: Ningning
authors.initials: N
authors.lastname: Xu
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom and Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
authors.forename: Xueqian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
authors.forename: Longqing
authors.initials: L
authors.lastname: Cong
authors.affiliation: Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
authors.forename: Jiaguang
authors.initials: J
authors.lastname: Han
authors.affiliation: School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA and Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
authors.forename: Weili
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhang