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arXiv 2009.08124cond-mat.supr-concond-mat.str-el
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二维系统中超过泡利顺磁极限的电荷密度波

Charge Density Waves beyond the Pauli paramagnetic limit in 2D systems

Alex Aperis, Georgios Varelogiannis

备注：
9 pages, 2 figures, preprint version
发表信息：
Journal of Applied Physics 128, 083901 (2020)
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摘要：

二维材料是承载电荷密度波（CDW）的理想候选者，其表现出顺磁限制行为，类似于众所周知的超导体的情况。在这里，我们研究如何CDW在二维系统中可以生存超过泡利极限时，他们受到一个强大的磁场通过开发一个广义的平均场论的CDW塞曼场，包括不可分割性，不完美的嵌套和温度效应和竞争或共存的自旋密度波（SDW）秩序的可能性。我们的数值计算产生丰富的相图与不同的高场相位以上的泡利极限场。对于完全嵌套的相称CDW，$q$调制的CDW相位，这是完全类似于超导Fulde-Ferrell-Larkin-Ovchinnikov（FFLO）相位出现在高场。在不完美嵌套的更常见的情况下，相称的CDW基态经历一系列磁场诱导的相变，首先进入相称的CDW和SDW共存的相位，随后进入另一个相位，其中CDW和SDW获得$q$调制，然而，该调制不同于纯FFLO CDW相位。相应的CDW+SDW相出现在与Pauli极限相当但小于Pauli极限的场中，并且在Pauli极限以上仍然存在。因此，该相提供了一种合理的机制，使得CDW在高场下仍然存在，而不需要形成更脆弱的FFLO相。我们认为，最近发现的二维材料，如过渡金属dichalcogenides提供了一个很有前途的平台，观察这种外来场诱导CDW现象。

英文摘要：

Two-dimensional materials are ideal candidates to host Charge density waves (CDWs) that exhibit paramagnetic limiting behavior, similarly to the well known case of superconductors. Here we study how CDWs in two-dimensional systems can survive beyond the Pauli limit when they are subjected to a strong magnetic field by developing a generalized mean-field theory of CDWs under Zeeman fields that includes incommensurability, imperfect nesting and temperature effects and the possibility of a competing or coexisting Spin density wave (SDW) order. Our numerical calculations yield rich phase diagrams with distinct high-field phases above the Pauli limiting field. For perfectly nested commensurate CDWs, a $q$-modulated CDW phase that is completely analogous to the superconducting Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase appears at high-fields. In the more common case of imperfect nesting, the commensurate CDW groundstate undergoes a series of magnetic-field-induced phase transitions first into a phase where commensurate CDW and SDW coexist and subsequently into another phase where CDW and SDW acquire a $q$-modulation that is however distinct from the pure FFLO CDW phase. The commensurate CDW+SDW phase occurs for fields comparable to but less than the Pauli limit and survives above it. Thus this phase provides a plausible mechanism for the CDW to survive at high fields without the need of forming the more fragile FFLO phase. We suggest that the recently discovered 2D materials like the transition metal dichalcogenides offer a promising platform for observing such exotic field induced CDW phenomena.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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