PT symmetry and spontaneous symmetry breaking in a microwave billiard.
We demonstrate the presence of parity-time (PT) symmetry for the non-Hermitian two-state Hamiltonian of a dissipative microwave billiard in the vicinity of an exceptional point (EP). The shape of the billiard depends on two parameters. The Hamiltonian is determined from the measured resonance spectrum on a fine grid in the parameter plane. After applying a purely imaginary diagonal shift to the Hamiltonian, its eigenvalues are either real or complex conjugate on a curve, which passes through the EP. An appropriate basis choice reveals its PT symmetry. Spontaneous symmetry breaking occurs at the EP.
Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany.
S
S
Bittner
B
B
Dietz
U
U
Günther
H L
HL
Harney
M
M
Miski-Oglu
A
A
Richter
F
F
Schäfer