We consider ionized hydrogen-like atoms accelerated by an external electric field to detect Unruh radiation. By applying quantum field theory in the Rindler spacetime, we show that the first-quantized description for hydrogen-like atoms cannot always be adopted. This is due to the frame-dependent definition of particles as positive and negative frequency field modes. We show how to suppress such a frame-dependent effect by constraining the atomic ionization and the electric field. We identify the physical regimes with nonvanishing atomic excitation probability due to the Unruh electromagnetic background. We recognize the observational limits for the Unruh effect via first-quantized atomic detectors, which appear to be compatible with current technology. Notably, the non-relativistic energy spectrum of the atom cannot induce coupling with the thermal radiation, even when special relativistic and general relativistic corrections are considered. On the contrary, the coupling with the Unruh radiation arises because of relativistic hyperfine splitting.
Probing Lorentz-invariance-violation with quantum coherence of Unruh-DeWitt detector
School of Physics, Hangzhou Normal University（杭州师范大学物理学院）；Department of physics and electrical engineering, Liupanshui Normal University（六盘水师范学院物理与电气工程系）
Acceleration radiation from vibrating atoms in Schwarzschild spacetime
Mapúa University（马普阿大学）；Eastern Mediterranean University（东地中海大学）；Westlake University（西湖大学）；Westlake Institute for Advanced Study（西湖高等研究院）；Zhejiang University（浙江大学）
