Nonreciprocal negative refraction in a dense hot atomic medium

We investigate the electromagnetic properties of a four-level dense atomic gas medium with Doppler effect. It is shown that the relative permittivity and relative permeability of the medium can be negative simultaneously with low absorption in the same detuning interval on account of electromagnetically induced transparency. Furthermore, with the suitable parameters, the nonreciprocal negative refraction can be obtained due to the Doppler effect, and the nonreciprocity frequency band can be regulated by adjusting the temperature, the intensity of the control field and the atomic density in this hot atomic medium.