1. Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
2. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
3. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
4. Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
5. CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China