FIELD-INDUCED NEW QUANTUM PHENOMENA IN MAGNETIC SYSTEMS

磁系统中场引发的新量子现象

• 批准号: 13130101
• 负责人: TANAKA Hidekazu
• 金额: $ 18.05万
• 依托单位: TOKYO INSTITUTE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research on Priority Areas
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13130101/
• 关键词: Magnetism; Experiments for Solid State Physics; Low Temperature Physics; Statistical Mechanics; High Magnetic Field; Quantum Spin Systems; Field-Induced Magnetic Phenomena; Low Dimensional Magnets; 強磁場物性; 高圧物性; スピンギャップ; 量子相転移; 量子効果; 新物質; フラス

We have developed many quantum magnets, which have various crystal structures, and have investigated their magnetic properties in high magnetic fields. Followings are representative results. Coupled S=1/2 spin dimer systems undergo novel quantum phase transitions in high magnetic fields. These systems often have singlet ground states with excitation gaps. In high magnetic field, one of the triplets whose energy decreases with magnetic field plays an important role. The triplet can hop to neighboring site as a quasi-particle and interact due to the transverse and longitudinal components of the interdimer exchange interaction. The quasi-particle has characteristics of boson and is called magnon or triplon. Consequently, the system can be described as interaction boson system, where magnetic field corresponds to the chemical potential. We found that the magnetization plateaus in SrCu_2(BO_3)_2 and other systems. The magnetization plateau can occur when the hopping of magnons are strongly … More suppressed due to spin frustration or parity and the periodic arrangement of magnons (Wigner crystal) are stabilized due to the repulsive interaction. This is a typical quantum many-body effect By means of NMR in high magnetic fields on SrCu_2(B0_3)_2, we verify the realization of Wigner crystal of magnons. On the other hand, the field-induced antiferromagnetic (AF) ordering occurs when the hopping of magnons is dominant The ordering can be described as the Bose-Einstein condensation (BEC) of magnons. We have performed various measurements on the field-induced AF ordering in TlCuCl_3. Together with theoretical analysis, we verify that the field-induced AF ordering in TlCuCl_3 is the BEC of magnons. The present study demonstrated that there are cases where the quantum magnets exhibit the nature characteristic of ensemble of quantum particles. This provides a new concept of magnetism.To encourage our research project, we organized three open symposiums inviting researchers from abroad and International Symposium on Quantum Spin Systems QSS04. We also supported three international meetings. Less

我们已经开发了许多具有不同晶体结构的量子磁体，并研究了它们在强磁场下的磁特性。以下是代表性结果。耦合的S=1/2自旋二聚体系统在强磁场下经历了新的量子相变。这些系统通常具有带激发能隙的单重基态。在强磁场中，能量随磁场减小的三重态之一起着重要作用。由于二聚体间交换相互作用的横向和纵向分量，三重态可以作为准粒子跳跃到相邻位点并相互作用。这种准粒子具有玻色子的特征，称为磁振子或三重子。因此，该系统可以被描述为相互作用玻色子系统，其中磁场对应于化学势。我们发现SrCu_2（BO_3）_2和其它体系的磁化强度都出现了平台。当磁振子的跃迁较强时， ...更多信息 由于自旋挫挫或宇称，磁振子的周期性排列被抑制，并且由于排斥相互作用，磁振子（维格纳晶体）的周期性排列被稳定。这是一个典型的量子多体效应。通过对SrCu_2（B0_3）_2在强磁场中的NMR研究，证实了磁振子Wigner晶体的实现。另一方面，当磁振子的跳跃占主导地位时，场诱导的反铁磁（AF）有序化可以描述为磁振子的玻色-爱因斯坦凝聚（BEC）。我们对TlCuCl_3中的场致AF有序进行了各种测量。结合理论分析，我们证实了TlCuCl_3中的场诱导AF有序是磁振子的BEC。本研究表明，在某些情况下，量子磁体表现出量子粒子系综的性质特征。为了鼓励我们的研究项目，我们组织了三次邀请国外研究人员参加的公开研讨会和量子自旋系统国际研讨会QSS 04。我们还支持了三次国际会议。少