Competing PT potentials and re-entrant PT symmetric phase for a particle in a box

Yogesh N. Joglekar, Bijan Bagchi

We investigate the effects of competition between two complex, \(\mathcal{PT}\)-symmetric potentials on the \(\mathcal{PT}\)-symmetric phase of a “particle in a box”. These potentials, given by \(V_Z(x)=iZ\mathrm{sign}(x)\) and \(V_\xi(x)=i\xi[\delta(x-a)-\delta(x+a)]\), represent long-range and localized gain/loss regions respectively. We obtain the \(\mathcal{PT}\)-symmetric phase in the \((Z,\xi)\) plane, and find that for locations \(\pm a\) near the edge of the box, the \(\mathcal{PT}\)-symmetric phase is strengthened by additional losses to the loss region. We also predict that a broken \(\mathcal{PT}\)-symmetry will be restored by increasing the strength \(\xi\) of the localized potential. By comparing the results for this problem and its lattice counterpart, we show that a robust \(\mathcal{PT}\)-symmetric phase in the continuum is consistent with the fragile phase on the lattice. Our results demonstrate that systems with multiple, \(\mathcal{PT}\)-symmetric potentials show unique, unexpected properties.
Quantum Physics (quant-ph)

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