Quantum metastability in time-dependent potentials
| Autor: | Chung-Chieh Lee, 李中傑 |
|---|---|
| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 In this dissertation we consider a quantum system with a state initially trapped by a static barrier potential, then instead of the static potential we investigate the quantum metastability of the system in two different classes of time-dependent barrier potentials. The first class of the barrier has expanding/contracting width and a specifically scaling barrier height. While deriving the non-decay probability of the system, we demonstrate that the appropriate technique to use is the less well known method of scattering states. For the case of the expanding width, we find that a small but finite non-decay probability persists at large time. Next, in the second class of the time-dependent potential we consider a barrier potential with a time-periodically oscillating height but a constant width. Unlike the method we used in our previous problem, we apply Floquet theory to the time-periodic system, and determine all possible metastable states of the system by numerical analysis. In our results we find that the time-periodically oscillating barrier will induce the metastable system to produce new metastable states by absorbing or emitting photons, and these new metastable states are less stable than the original time-independent one. But we also find as the frequency of the oscillating barrier exceeds a critical frequency, besides absorbing or emitting photons the system also has ability to preserve its original metastable state, and its stability is superior to the one without time-periodically oscillating barrier. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|