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

这个低温物理职业项目将使用超声光谱技术来研究纯净和肮脏的超流体3He的基本性质。我们将研究强磁场(高达15T)对含有磁性和非磁性杂质的脏p波超流体的影响。这项工作将提供关于这一相对较新系统相图的重要信息，并有可能揭示临界压力附近的新现象。临界压强与量子相变有关，量子相变在一系列凝聚态系统中引起了极大的兴趣。利用横向声谱技术，将研究在B相中存在亚主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新的集体模方面优于传统的方法，这些新的集体模的存在仅由f波对相互作用保证。新模式的观测将是对更一般的超流体中次优配对相互作用产生的集体模式的第一次实验证实。我们将使用零声来研究跃迁上方的涨落效应。已知的背景贡献和零声速测量中极高的分辨率将有助于直接测量相干长度。这个低温物理职业项目将使用超声光谱技术研究纯净和所谓的脏超流体3He的基本性质。肮脏的超流体是指存在密度极低的多孔固体(如气凝胶)的超流体样本。这项在绝对零度附近进行的研究，不仅与量子流体团体、研究3He和4He性质的科学家有关，还与凝聚态物理的许多其他领域有关。近年来，人们在各种凝聚态系统中发现并广泛研究了许多与量子相变相关的有趣现象。与传统的(经典)相变不同的是，量子相变发生在有限的温度，如固体的熔化，量子相变是从纯粹的量子力学起源触发的，因此可以在绝对零度发生。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3He相图的影响。在另一项工作中，将利用一种新的横向声谱技术，通过寻找(3He原子的)库珀对的新激发态，来研究纯超流3He超流的详细微观起源。我们将通过进行高分辨率声速测量来研究高于、但接近转变温度的初始超流性。初始超流是由短寿命的库珀对的热驱动涨落引起的。这项研究涉及研究生和本科生的广泛参与，他们将为以后在学术界、行业或政府的职业机会提供广泛的严格实验室经验和培训。该研究项目包括一个重要的组成部分，旨在改善当地高中的科学教育。

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.