Pinotti Ermanno, Longhi Stefano
Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy.
IFISC (UIB-CSIC), Instituto de Fisica Interdisciplinar y Sistemas Complejos, E-07122 Palma de Mallorca, Spain.
Entropy (Basel). 2023 Sep 16;25(9):1345. doi: 10.3390/e25091345.
A quantum particle constrained between two high potential barriers provides a paradigmatic example of a system sustaining quasi-bound (or resonance) states. When the system is prepared in one of such quasi-bound states, the wave function approximately maintains its shape but decays in time in a nearly exponential manner radiating into the surrounding space, the lifetime being of the order of the reciprocal of the width of the resonance peak in the transmission spectrum. Naively, one could think that adding more lateral barriers would preferentially slow down or prevent the quantum decay since tunneling is expected to become less probable and due to quantum backflow induced by multiple scattering processes. However, this is not always the case and in the early stage of the dynamics quantum decay can be accelerated (rather than decelerated) by additional lateral barriers, even when the barrier heights are arbitrarily large. The decay acceleration originates from resonant tunneling effects and is associated to large deviations from an exponential decay law. We discuss such a counterintuitive phenomenon by considering the hopping dynamics of a quantum particle on a tight-binding lattice with on-site potential barriers.
一个被限制在两个高势垒之间的量子粒子提供了一个维持准束缚（或共振）态系统的典型例子。当系统处于这样一种准束缚态时，波函数大致保持其形状，但会随着时间以近似指数的方式衰减，并向周围空间辐射，其寿命约为透射谱中共振峰宽度的倒数。直观地说，人们可能会认为增加更多的横向势垒会优先减缓或阻止量子衰变，因为预计隧穿的可能性会降低，并且由于多重散射过程引起的量子回流。然而，情况并非总是如此，在动力学的早期阶段，即使势垒高度任意大，额外的横向势垒也可以加速（而不是减速）量子衰变。衰变加速源于共振隧穿效应，并且与指数衰变定律的大偏差有关。我们通过考虑具有在位势垒的紧束缚晶格上量子粒子的跳跃动力学来讨论这种反直觉现象。
