Читать книгу Quantum Mechanics, Volume 3 - Claude Cohen-Tannoudji - Страница 106

Consider now a system of repulsive bosons contained in a toroidal box with a rotational axis Oz (Figure 2); the shape of the torus cross-section (circular, rectangular or other) is irrelevant for our argument and we shall use cylindrical coordinates r, φ and z. We first introduce solutions of the Gross-Pitaevskii equation that correspond to the system rotating inside the toroidal box, around the Oz axis. We will then show that these rotational states are metastable, as they can only relax towards lower energy rotational states by overcoming a macroscopic energy barrier: this is the physical origin of superfluidity.