Babaev Egor, Sudbø Asle, Ashcroft N W
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York, 14853-2501, USA.
Nature. 2004 Oct 7;431(7009):666-8. doi: 10.1038/nature02910.
Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids.
尽管氢是最简单的原子，但它形成的固体或液体却并非最简单。这些物相中的量子效应相当显著（这是质子质量轻的结果），并且对包括空间有序性在内的许多物理性质有着明显且常常令人费解的影响。迄今为止，致密氢的结构在实验上仍然难以捉摸。近期对氢的熔化曲线的研究表明，在高（但实验上可达到）压力下，即使在低温时，压缩氢也会呈现液态。在达到这个物相的过程中，氢还预计会经历从绝缘体到金属的转变。这就引发了一种新物质状态的可能性：一种接近基态的液态金属及其在量子领域中的有序状态。传统上，有序量子流体被归类为超导体或超流体；这些各自的系统具有无耗散电流或质量流的特征。在此，我们报告了对预计的液态金属氢物相的拓扑分析，发现它可能代表一种新型的有序量子流体。具体而言，我们表明液态金属氢不能仅仅归类为超导体或超流体。我们预测，在有磁场存在的情况下，液态金属氢将展现出从超导体到超流体等多种向有序状态的相变。
