Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Phys Rev Lett. 2009 Oct 2;103(14):140402. doi: 10.1103/PhysRevLett.103.140402. Epub 2009 Sep 28.
We prove the absence of a direct quantum phase transition between a superfluid and a Mott insulator in a bosonic system with generic, bounded disorder. We also prove the compressibility of the system on the superfluid-insulator critical line and in its neighborhood. These conclusions follow from a general theorem of inclusions, which states that for any transition in a disordered system, one can always find rare regions of the competing phase on either side of the transition line. Quantum Monte Carlo simulations for the disordered Bose-Hubbard model show an even stronger result, important for the nature of the Mott insulator to Bose glass phase transition: the critical disorder bound Delta(c) corresponding to the onset of disorder-induced superfluidity, satisfies the relation Delta(c)>Eg/2, with Eg/2 the half-width of the Mott gap in the pure system.
我们证明了在具有一般、有界无序的玻色系统中，超流相与莫特绝缘相之间不存在直接的量子相变。我们还证明了系统在超流-绝缘相变线上及其附近的压缩性。这些结论源自于一个广义的包含定理，该定理指出，对于无序系统中的任何相变，都可以在相变线的任意一侧找到竞争相的稀有区域。针对无序玻色-哈伯德模型的量子蒙特卡罗模拟则显示出了更为强大的结果，这对莫特绝缘相到玻色玻璃相变的本质非常重要：与无序诱导超流出现相对应的临界无序边界 Delta(c)，满足关系 Delta(c)>Eg/2，其中 Eg/2 是纯净系统中莫特能隙的半宽度。
