CAREER: Fundamental Discovery with Solid-State Spin Ensembles

该奖项的部分资金来自《2021年美国救援计划法案》(公法117-2)。暗物质的性质是现代科学中最基本的开放问题之一。随着对暗物质的研究取得进展，轴子和类轴子粒子已经成为特别引人注目的候选粒子。轴子是从被称为强CP问题的模型解中自然产生的。对这些粒子的搜索为了解超高能物理打开了一扇实验窗口，最高可达普朗克尺度，而类轴子暗物质的发现将为我们提供对宇宙最早演化阶段的潜在洞察。这项职业奖支持开发基于固态电子和核自旋系综和磁传感的精密实验室实验平台，以推进在纳电子伏特到皮电子伏特质量范围内具有灵敏度的轴子和轴子类粒子的搜索。该奖项将开发一个面向年轻学生和普通公众的外展计划，重点是培养复杂现实世界挑战的非标准解决问题的技能。该计划将与波士顿大学Growth和MIT BLOOMS计划合作，开发与宇宙和暗物质研究有关的新型在线内容，并将重点与波士顿地区的学校建立联系，该地区有大量来自STEM代表不足的群体的学生。该奖项利用了利用铁磁环晕(SHAIL)实验平台寻找晕轴子所取得的既定技术成果。具体地说，该平台在10 kHz到1 MHz的范围内实现了每平方根(Hz)150的磁场灵敏度，这是使用宽带磁强计技术进行的最灵敏的磁场测量。作为获奖活动的一部分，计划进行两项主要测量。第一个将在0.1K温度下的稀释冰箱中运行设备的SQUID传感器，以提高对类似轴子的暗物质的电磁耦合的敏感度，大约为3E-12GeV，质量接近20皮电子伏。这一测量将比目前的实验灵敏度提高一个数量级以上。第二次互补测量将通过将固体晶体集成到磁传感设备中来实现，这些固体晶体承载着一整套核自旋，为搜索由轴子状暗物质的电火花相互作用引起的时变核电偶极矩(EDM)而优化。搜索将涉及高分辨率光学光谱学和测量核自旋弛豫参数，目标是通过直接光学泵浦实现20%的核自旋极化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The nature of dark matter is one of the most fundamental open questions of modern science. As searches for the dark matter have advanced, axions - that arise naturally from model solutions of what is known as the strong-CP problem - and axion-like particles have emerged as particularly compelling candidates. The search for these particles opens an experimental window into physics at ultra-high energy scales, up to the Planck-scale, and discovery of axion-like dark matter would provide potential insight into the earliest evolutionary stages of the Universe. This CAREER award supports the development of a precision laboratory experimental platform based on solid-state electron and nuclear spin ensembles and magnetic sensing to advance the search for axions and axion-like particles with sensitivity in the nano-electronvolt to pico-electronvolt mass range. The award will develop an outreach program directed toward young students and the general public with a focus on developing non-standard problem-solving skills of complex real-world challenges. This program will partner with the Boston University GROW and MIT BLOSSOMS programs to develop novel online content with connections to the study of the cosmos and dark matter, and will focus on building connections with schools in the Boston-area with large populations of students from underrepresented groups in STEM.This award leverages the established technical achievements of the Search for Halo Axions with Ferromagnetic Toroids (SHAFT) experimental platform. Specifically, the platform realizes a magnetic field sensitivity of 150 aT per square root(Hz) over a range of 10 kHz to 1 MHz, representing the most sensitive magnetic field measurement with a broadband magnetometer technology. Two primary measurements are planned as a part of the awarded activities. The first will operate the apparatus’ SQUID sensors within a dilution refrigerator at 0.1K temperature to improve the sensitivity to the electromagnetic coupling of axion-like dark matter to approximately 3e-12 GeV near 20 pico-electronvolt mass. This measurement would represent more than an order of magnitude improvement over current experimental sensitivities. The second complementary measurement will be made possible by integrating into the magnetic sensing apparatus solid crystals that host ensembles of nuclear spins, optimized for searches for time-varying nuclear electric dipole moments (EDMs) induced by the EDM interaction of axion-like dark matter. The search will involve high-resolution optical spectroscopy and measurements of the nuclear spin relaxation parameters, with the goal of achieving 20 percent nuclear spin polarization by direct optical pumping.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.