熵驱动的热磁振子交替磁性

中文摘要 AI 辅助

我们确定了一条由熵在加热时驱动交替磁性的途径，并在一个最小方格子反铁磁体中演示了它。交换调制在熵上是有利的，因为由此产生的动量相关磁振子分裂增加了磁振子熵，从而降低了自由能并有利于交替磁性。我们推导了这种交换调制态的不稳定性判据，预测了其温度驱动的重入行为，并表明其与奈尔序的重叠定义了一个有限温度交替磁性相。变分自旋波理论、自旋-晶格蒙特卡洛和团簇对角化确立了熵驱动的不稳定性及其与磁序的共存。所得态支持横向自旋电导率。该机制为在耦合到足够软的物理模式的补偿磁体中热诱导交替磁性提供了一条途径。

英文摘要

We identify a route to altermagnetism driven by entropy upon heating and demonstrate it in a minimal square-lattice antiferromagnet. An exchange modulation is entropically favored because the resulting momentum-dependent magnon splitting increases the magnon entropy, thereby lowering the free energy and favoring altermagnetism. We derive an instability criterion for this exchange-modulated state, predict its temperature-driven reentrant behavior, and show that its overlap with Néel order defines a finite-temperature altermagnetic phase. Variational spin-wave theory, spin--lattice Monte Carlo, and cluster diagonalization establish the entropy-driven instability and its coexistence with magnetic order. The resulting state supports a transverse spin conductivity. The mechanism provides a route to thermally induced altermagnetism in compensated magnets coupled to sufficiently soft physical modes.

发表机构

• School of Physical Sciences, National Institute of Science Education and Research（国家科学教育研究中心物理科学学院）
• Homi Bhabha National Institute（霍米·巴巴国立研究所）

机构由 AI 辅助整理，请以论文原文为准。