Leggett Modes Accompanying Crystallographic Phase Transitions
Leggett Modes Accompanying Crystallographic Phase Transitions
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DOI：
10.1103/physrevx.12.011024
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发表时间：
2021-07
影响因子：
12.5
通讯作者：
Q. Meier;D. Hickox-Young;Geneva Laurita;N. Spaldin;J. Rondinelli;M. Norman
中科院分区：
文献类型：
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作者：
Q. Meier;D. Hickox-Young;Geneva Laurita;N. Spaldin;J. Rondinelli;M. Norman
希格斯模式和戈德斯通模式在高能物理学中众所周知，已在许多凝聚态物理背景中实现，包括超导和磁性。戈德斯通-希格斯概念也适用于结构相变，并带来了关于结构相变的新见解。在这里，我们证明了莱格特模式（在多带超导体中观察到的集体模式）在晶体相变中也有类似物。这种结构 Leggett 模式可以出现在相位通道中，如 Leggett 的原始作品 \href{https://doi.org/10.1143/PTP.36.901}{Prog.\ Theor.\ Phys.\ \textbf{36}, 901 (1966)}。也就是说，它们是反相戈德斯通模式（反相子）。此外，振幅通道中还可能出现一种新的集体模式，即异相（反相）希格斯模式，这也应该在多带超导体中观察到。我们使用烧绿石弛豫铁电体 Cd$_2$Nb$_2$O$_7$ 的例子来说明这些结构 Leggett 模式的存在和性质。
Higgs and Goldstone modes, well known in high energy physics, have been realized in a number of condensed matter physics contexts, including superconductivity and magnetism. The Goldstone-Higgs concept is also applicable to and gives rise to new insights on structural phase transitions. Here, we show that the Leggett mode, a collective mode observed in multi-band superconductors, also has an analog in crystallographic phase transitions. Such structural Leggett modes can occur in the phase channel as in the original work of Leggett, \href{https://doi.org/10.1143/PTP.36.901}{Prog.\ Theor.\ Phys.\ \textbf{36}, 901 (1966)}. That is, they are antiphase Goldstone modes (anti-phasons). In addition, a new collective mode can also occur in the amplitude channel, an out-of phase (antiphase) Higgs mode, that should be observable in multi-band superconductors as well. We illustrate the existence and properties of these structural Leggett modes using the example of the pyrochlore relaxor ferroelectric, Cd$_2$Nb$_2$O$_7$.