I shall discuss nonreciprocal particle and energy transport in linear systems with balanced gain and loss of particles or energy in the bulk  [1]. The role of balanced gain and loss of particles or energies has been extensively investigated in recent years in the context of an effective parity-time symmetry in classical and quantum systems. First, I shall point out severe issues with existing theoretical modeling for the time evolution of such systems [2]. Next, I shall present our studies of these systems within an open-quantum system and a classical master equation description. These descriptions surprisingly lead to nonreciprocal transport in linear systems, even without magnetic fields. Previous studies have found nonreciprocity in such models only due to nonlinearity or magnetic fields. Our results suggest that these systems with broken parity and time-reversal symmetry show an arrow of space manifested through nonreciprocal transport.

References:

1. Nonreciprocal electrical transport in linear systems with balanced gain and loss in the bulk, Rupak Bag and Dibyendu Roy, arXiv: 2409.12510 (2024)

2. Quantum noise induced nonreciprocity for single photon transport in parity-time symmetric systems, Dibyendu Roy and G. S. Agarwal, arXiv: 2407.00758 (2024)