CAREER: Nature of Pure and Dirty Liquid 3He-Fundamental Investigations and Educational Activities

这个低温物理CAREER项目将使用超声光谱技术研究纯超流体和脏超流体3He的基本性质。强磁场（高达15 T）对存在磁性和非磁性杂质的脏p波超流体的影响将被研究。这项工作将为这个相对较新的系统的相图提供重要的信息，并有可能揭示临界压力附近的新现象。临界压力与量子相变有关，量子相变在一系列凝聚态系统中引起了极大的兴趣。使用横向声光谱技术，将研究b相中次优势f波配对相互作用的直接证据。这种新的光谱技术被认为在寻找仅由f波对相互作用保证存在的新集体模式方面优于传统的技术。对新模态的观察将是对在更一般的超流体中由亚优势配对相互作用产生的集体模态的第一次实验证实。跃迁以上的波动效应将用零声来研究。已知的背景贡献和零声速测量中的极高分辨率将有助于直接测量相干长度。这个低温物理CAREER项目将使用超声波光谱技术研究纯超流体和所谓的脏超流体3He的基本性质。脏超流体是指存在密度非常低的多孔固体（如气凝胶）的超流体样品。这项研究在接近绝对零度的温度下进行，不仅与量子流体界、研究3He和4He性质的科学家有关，而且与凝聚态物理的许多其他领域有关。近年来，在各种凝聚态体系中发现了许多与量子相变有关的有趣现象，并进行了广泛的研究。与传统的（经典的）转变不同，它发生在有限的温度下，如固体的熔化，量子相变是由纯粹的量子力学起源触发的，因此可以在绝对零度下发生。脏超流体系统是研究这种量子相变的一个很好的系统，特别是在临界压力附近。研究了强磁场对无序超流体3He相图的影响。在其他工作中，将使用一种新的横向声光谱技术，通过寻找（3He原子的）库珀对的新激发态，来研究纯超流体3He中超流体的详细微观起源。通过高分辨率声速测量，将研究在过渡温度以上但附近的初始超流动性。初期超流动性是由寿命短的库珀对的热驱动波动引起的。这项研究涉及研究生和本科生的广泛参与，他们将获得广泛的严格的实验室经验和培训，为以后在学术界、工业界或政府的职业发展提供机会。该研究项目包括一个重要的组成部分，旨在改善当地高中科学教育。

This low temperature physics CAREER project will investigate the fundamental nature of pure and dirty superfluid 3He using ultrasound spectroscopic techniques. The effect of strong magnetic fields (up to 15 T) on the dirty p-wave superfluid in the presence of magnetic and non-magnetic impurities will be investigated. This work will provide important information on the phase diagram of this relatively new system and has the potential to reveal new phenomena near the critical pressure. The critical pressure is related to quantum phase transitions, which are of great current interest in a range of condensed matter systems. Using a transverse sound spectroscopic technique, direct evidence of a sub-dominant f-wave pairing interaction in the B-phase will be investigated. This novel spectroscopic technique is believed to be superior to the conventional technique in searching for the new collective modes whose existence is guaranteed only by the f-wave pairing interaction. The observation of the new mode would be the first experimental confirmation of the collective modes generated by the subdominant pairing interaction in a more general class of superfluids. Fluctuation effects above the transition will be studied using zero sound. The known background contribution and an extremely high resolution in the zero sound velocity measurements will facilitate the direct measurement of the coherence length. This low temperature physics CAREER project will investigate fundamental properties of pure and so-called dirty superfluid 3He using ultrasound spectroscopic techniques. Dirty superfluid refers to superfluid samples in the presence of very low-density porous solids, such as an aerogel. The research, near the absolute zero of temperature, is relevant not only to the quantum fluids community, scientists who investigate the properties of 3He and 4He, but to many other areas of condensed matter physics. Recently, many interesting phenomena related to quantum phase transitions have been discovered and studied extensively in various condensed matter systems. Unlike conventional (classical) transitions, which occur at finite temperatures such as melting of solids, quantum phase transitions are triggered from purely quantum mechanical origins and accordingly can occur at absolute zero temperature. The dirty superfluid system is an excellent system to study this quantum phase transitions especially near the critical pressure. The effect of strong magnetic fields on the phase diagram of disordered superfluid 3He will be investigated. In other work, the detailed microscopic origin of superfluidity in pure superfluid 3He will be investigated via a search for a new excited state of the Cooper pairs (of 3He atoms) using a novel transverse sound spectroscopic technique. The incipient superfluidity above, but near, the transition temperature will be studied by conducting high resolution sound velocity measurements. The incipient superfluidity is caused by the thermally driven fluctuations of Cooper pairs with a short lifetime. The research involves extensive participation of both graduate and undergraduate students, who will be provided a wide range of rigorous laboratory experience and training for later career opportunities in academe, industry or government. The research project includes an important integral component directed toward improving local high school science education.