LPEM (UPMC-CNRS), Ecole Supérieure de Physique et de Chimie Industrielles, 75005 Paris, France.
Phys Rev Lett. 2013 Jun 28;110(26):266601. doi: 10.1103/PhysRevLett.110.266601. Epub 2013 Jun 25.
Different instabilities have been speculated for a three-dimensional electron gas confined to its lowest Landau level. The phase transition induced in graphite by a strong magnetic field, and believed to be a charge density wave, is the only experimentally established case of such instabilities. Studying the magnetoresistance in graphite for the first time up to 80 T, we find that the magnetic field induces two successive phase transitions, consisting of two distinct ordered states each restricted to a finite field window. In both states, an energy gap opens up in the out-of-plane conductivity and coexists with an unexpected in-plane metallicity for a fully gap bulk system. Such peculiar metallicity may arise as a consequence of edge-state transport expected to develop in the presence of a bulk gap.
人们推测，在被限制在最低朗道能级的三维电子气中存在多种不稳定性。在磁场作用下石墨中发生的相变被认为是一种电荷密度波，这是唯一一种被实验证实的不稳定性情况。我们首次在高达 80 T 的磁场下研究了石墨的磁电阻，发现磁场诱导了两个连续的相变，每个相变都由两个受限在有限磁场窗口内的有序状态组成。在这两种状态下，面外电导率出现能隙，同时在完全能隙体系统中出人意料地出现面内金属性。这种特殊的金属性可能是由于在体隙存在的情况下预期会出现的边缘态输运所致。
