Phase transition related thermal radiation in gated bilayer graphene

The presence of interlayer potential, Rashba spin–orbit coupling and exchange field in bilayer graphene leads to a topological phase transition. We theoretically calculate the optical conductivity, radiation spectrum and energy radiation in gated bilayer graphene with only interlayer potential and Rashba spin–orbit coupling. The sharp peaks of longitudinal conductivity at low frequency contribute more to energy radiation. The quantum valley Hall insulator and strong topological insulator phases can be distinguished by energy radiation. When the exchange field is also turned on, time-reversal symmetry is broken. As a result, bilayer graphene has net angular momentum radiation. Compared with the phase diagram, the quantum valley Hall insulator and quantum anomalous Hall insulator phases can also be distinguished by energy and angular momentum radiation. The gate voltage in conjunction with proper Rashba SOC and exchange field can serve as effective tuning method to adjust energy or angular momentum radiation.