CAREER: Fundamental Discovery with Solid-State Spin Ensembles

该奖项部分由2021年美国救援计划法案（公法117-2）资助。暗物质的本质是现代科学中最基本的开放性问题之一。随着对暗物质搜索的深入，轴子——从强cp问题的模型解中自然产生的——和类轴子粒子已经成为特别引人注目的候选者。对这些粒子的探索打开了一扇实验窗口，让我们了解超高能量尺度的物理学，直到普朗克尺度，而发现类似轴子的暗物质将为我们了解宇宙最早的进化阶段提供潜在的视角。该CAREER奖支持基于固态电子和核自旋综和磁传感的精密实验室实验平台的开发，以推进对具有纳米电子伏特到皮电子伏特质量范围灵敏度的轴子和轴子样粒子的搜索。该奖项将开发一个面向年轻学生和公众的推广项目，重点是培养解决复杂现实世界挑战的非标准问题的技能。该项目将与波士顿大学GROW和麻省理工学院BLOSSOMS项目合作，开发与宇宙和暗物质研究有关的新颖在线内容，并将重点与波士顿地区的学校建立联系，这些学校有大量来自STEM领域代表性不足群体的学生。该奖项利用了铁磁环体（SHAFT）实验平台搜索光环轴子的既定技术成果。具体而言，该平台在10 kHz至1 MHz的范围内实现了150 aT /平方根（Hz）的磁场灵敏度，代表了宽带磁强计技术中最灵敏的磁场测量。作为授予活动的一部分，计划进行两项主要测量。第一个将在0.1K的温度下在稀释冰箱中操作仪器的SQUID传感器，以提高对轴子样暗物质电磁耦合的灵敏度，使其达到约3e-12 GeV，接近20皮电子伏质量。这一测量将比目前的实验灵敏度提高一个数量级以上。第二次补充测量将通过集成到磁传感装置中实现，该装置包含核自旋集合，优化用于搜索由轴子样暗物质的EDM相互作用引起的时变原子核电偶极矩（EDM）。这项研究将涉及高分辨率光谱学和核自旋弛豫参数的测量，目标是通过直接光泵浦实现20%的核自旋极化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.