Department of Physics, Massachusetts Institute of Technology, Cambridge, 02139, USA.
Phys Rev Lett. 2012 Aug 17;109(7):077205. doi: 10.1103/PhysRevLett.109.077205. Epub 2012 Aug 16.
We describe a new possible route to the metal-insulator transition in doped semiconductors such as Si:P or Si:B. We explore the possibility that the loss of metallic transport occurs through Mott localization of electrons into a quantum spin liquid state with diffusive charge neutral "spinon" excitations. Such a quantum spin liquid state can appear as an intermediate phase between the metal and the Anderson-Mott insulator. An immediate testable consequence is the presence of metallic thermal conductivity at low temperature in the electrical insulator near the metal-insulator transition. Further, we show that though the transition is second order, the zero temperature residual electrical conductivity will jump as the transition is approached from the metallic side. However, the electrical conductivity will have a nonmonotonic temperature dependence that may complicate the extrapolation to zero temperature. Signatures in other experiments and some comparisons with existing data are made.
我们描述了掺杂半导体（如 Si:P 或 Si:B）中金属-绝缘转变的一种新的可能途径。我们探讨了电子通过莫特局域化进入具有扩散电荷中性“自旋子”激发的量子自旋液体状态，从而导致金属输运丧失的可能性。这样的量子自旋液体状态可以出现在金属和安德森-莫特绝缘体之间的中间相。一个可以立即检验的结果是，在金属-绝缘转变附近的电绝缘体中，低温下存在金属热导率。此外，我们表明，尽管转变是二级相变，但当从金属侧接近转变时，零温剩余电导率将跳跃。然而，电导率将具有非单调的温度依赖性，这可能会使向零温的外推复杂化。在其他实验中找到了一些特征，并与现有数据进行了一些比较。
