Observation of continuum Landau modes in non-Hermitian electric circuits

Observation of continuum Landau modes in non-Hermitian electric circuits

27 February 2024 | Xuwei Zhang, Chaohua Wu, Mou Yan, Ni Liu, Ziyu Wang & Gang Chen
This study reports the experimental observation of continuum Landau modes (CLMs) in non-Hermitian electric circuits. CLMs are continuous bound states predicted in non-Hermitian Dirac Hamiltonians under uniform magnetic fields, which differ from the quantized Landau levels in Hermitian systems. The non-Hermitian Dirac Hamiltonian was simulated using non-reciprocal hoppings and a pseudomagnetic field was introduced via inhomogeneous complex on-site potentials. By measuring the admittance spectrum and eigenstates, the key features of CLMs were successfully verified. Notably, an exotic voltage response was observed, acting as a rainbow trap or wave funnel through full-field excitation, arising from the linear relationship between the CLMs' center position and complex eigenvalues. The work bridges non-Hermiticity and magnetic fields, opening new avenues for exploring non-Hermitian physics. CLMs were observed in both 2D and 1D non-Hermitian electric circuits. In the 2D case, the CLMs exhibited a Gaussian spatial envelope and formed a continuous spectrum filling the complex energy plane. The eigenstates were localized and their center positions were linearly related to the complex eigenvalues. In the 1D case, the CLMs were centered at positions proportional to the eigenvalues, demonstrating behaviors of rainbow trapping or wave funneling. The experiments confirmed the robustness of CLMs, showing that the linear relationship between the center position and complex eigenvalues persisted even with increased circuit component errors. The study provides a platform to explore non-Hermitian physics driven by magnetic fields. The results highlight the unique properties of non-Hermitian systems, including complex energy spectra, exceptional points, and the skin effect, and their potential applications in sensing, lasing, and wave manipulation. The experimental observations validate the theoretical predictions and demonstrate the feasibility of using non-Hermitian electric circuits to study exotic quantum phenomena.This study reports the experimental observation of continuum Landau modes (CLMs) in non-Hermitian electric circuits. CLMs are continuous bound states predicted in non-Hermitian Dirac Hamiltonians under uniform magnetic fields, which differ from the quantized Landau levels in Hermitian systems. The non-Hermitian Dirac Hamiltonian was simulated using non-reciprocal hoppings and a pseudomagnetic field was introduced via inhomogeneous complex on-site potentials. By measuring the admittance spectrum and eigenstates, the key features of CLMs were successfully verified. Notably, an exotic voltage response was observed, acting as a rainbow trap or wave funnel through full-field excitation, arising from the linear relationship between the CLMs' center position and complex eigenvalues. The work bridges non-Hermiticity and magnetic fields, opening new avenues for exploring non-Hermitian physics. CLMs were observed in both 2D and 1D non-Hermitian electric circuits. In the 2D case, the CLMs exhibited a Gaussian spatial envelope and formed a continuous spectrum filling the complex energy plane. The eigenstates were localized and their center positions were linearly related to the complex eigenvalues. In the 1D case, the CLMs were centered at positions proportional to the eigenvalues, demonstrating behaviors of rainbow trapping or wave funneling. The experiments confirmed the robustness of CLMs, showing that the linear relationship between the center position and complex eigenvalues persisted even with increased circuit component errors. The study provides a platform to explore non-Hermitian physics driven by magnetic fields. The results highlight the unique properties of non-Hermitian systems, including complex energy spectra, exceptional points, and the skin effect, and their potential applications in sensing, lasing, and wave manipulation. The experimental observations validate the theoretical predictions and demonstrate the feasibility of using non-Hermitian electric circuits to study exotic quantum phenomena.
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