PT Symmetry of a Square-Wave Modulated Two-Level System
PT Symmetry of a Square-Wave Modulated Two-Level System
复制标题
方波调制两电平系统的 PT 对称性
DOI：
10.1088/0256-307x/37/8/081101
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发表时间：
2020
影响因子：
3.5
通讯作者：
Chen Qing-Hu
中科院分区：
文献类型：
--
作者：
Duan Liwei Wang;Wang Yan-Zhi;Chen Qing-Hu
We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling. Based on the Floquet theory, we achieve an effective Hamiltonian from which the boundaries of the PT phase diagram are captured exactly. Two kinds of PT symmetry broken phases are found, whose effective Hamiltonians differ by a constant ω/2. For the time-periodic dissipation, a vanishingly small dissipation strength can lead to the PT symmetry breaking in the (2k – 1)-photon resonance (Δ = (2k – 1) ω), with k = 1,2,3… It is worth noting that such a phenomenon can also happen in 2k-photon resonance (Δ = 2kΔ), as long as the dissipation strengths or the driving times are imbalanced, namely γ0 ≠ – γ1 or T0 ≠ T1. For the time-periodic coupling, the weak dissipation induced PT symmetry breaking occurs at Δeff = kω, where Δeff = (Δ0T0 + Δ1T1)/T. In the high frequency limit, the phase boundary is given by a simple relation γeff = ±Δeff.
