AC CONDUCTANCE OF A DOUBLE-BARRIER RESONANT TUNNELING SYSTEM UNDER A DC-BIAS VOLTAGE

An analytical path-integral method based on the nonequilibrium Greens function is developed to investigate the linear response of a double-barrier resonant-tunneling system under a small ac signal which is superimposed upon a dc bias. When the dc-bias voltage is zero, our calculated ac conductance reduces back to that of a recent Kubo-formula study. When the system is biased at the negative differential resistance point, both the real (negative) conductance and imaginary part of admittance are derived. Comparisons with previous numerical study and experiments are discussed. © 1990 The American Physical Society.