我们简要回顾了量子自旋液体概念的提出及最初阶段的发展及演化,重点不是对这个快速发展领域的研究状况作较系统的评述,而是关注概念的出发点及面临的困难并分析可能的原因:通过声称自旋不做什么并不是一个好的出发点。通过考察自旋做什么应该能够提供一个量子自旋液体直接定义的可能的出发点。对阻挫自旋-1/2
反铁磁方格子模型的分析,表明图案语言能够描述小
区域和大
区域的长程序。这样,没有理由怀疑它不能描述中间
区间自旋的行为:对角单畴(Néel反铁磁)→ 对角双畴→ 对角四畴→ 对角六畴→......→对角
畴(striped反铁磁)。图案语言提供的对角畴的演化过程,相信能够为量子自旋液体的直接定义及各种可能的相和相变的刻画提供见解。对目前
周期性格点,最强阻挫区域的物理可以用一句俗语较为准确地表达:“山中无老虎,猴子称霸王”。
目前的结果只限于正方格子的小格点尺寸。增加格点尺寸和应用到另外的格点如三角格点、honeycomb格点、Kagomé格点等将会提供更加丰富的行为,但上面的图像应该保持有效。
我们仍然以《西游记》电视剧主题曲结束本文,“敢问路在何方?路在脚下”。
致谢:特别感谢基金委理论物理专款对“兰州大学理论物理交流平台”(2010-2020)和“兰州理论物理中心”(2021-)的支持和甘肃省科技厅对“甘肃省理论物理重点实验室”的支持。
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