The results were published in two manuscripts backtoback in Physical Review Letters, one focusing on the experimental investigation [121, 086806 (2018)], while the second one presents the theoretical investigation based on numerical simulations [121, 086805 (2018)].
Noise is usually an annoyance to be avoided and minimized for practical applications. However, sometimes it plays a constructive role that can be exploited to produce useful results. Applying noise in combination with smallamplitude periodic oscillations to a nonlinear system can result in very intricate effects. Noise can drive a stationary system into an oscillatory state with coherent current selfoscillations having tunable frequencies between zero and about 100 MHz, which is called a coherence resonance. By adding to the noise smallamplitude periodic oscillations with a frequency close to that of the current selfoscillations, the nonlinear system can be phase locked to the coherence resonance, which is referred to as a stochastic resonance. This stochastic resonance can be used as a passive lockin amplifier, without a reference signal and with a much shorter integration time than available for conventional lockin amplifiers. Until now, all methods detecting weak signals are actively based on the correlation with a known reference signal, and it is impossible to identify unknown signals hidden in a background with strong noise. Typical lockin amplifiers need a reference signal in the tens of Hz to MHz range and integration times of the order of milliseconds. The wide frequency range of the coherence resonance allows for the operation without any reference signal and to extraordinarily reduce the integration time necessary to process the signal.
The research team has experimentally demonstrated the occurrence of coherence and stochastic resonances at room temperature in a doped, weakly coupled GaAs/(Al,Ga)As superlattice with 45% Al. Numerical simulations of the electron transport based on a discrete sequential tunneling model carried out simultaneously reproduce these results qualitatively very well. In addition, the theoretical model can be used to determine the devicedependent critical current for the coherence resonance directly from the experimental results.
2  Author  E. Mompo , M. RuizGarcia , M. Carretero , H. T. Grahn , Y. H. Zhang , L. L. Bonilla 
Title 
Coherence Resonance and Stochastic Resonance in an Excitable Semiconductor Superlattice 

Source  Phys. Rev. Lett. , 121 , 086805 ( 2018 )  
DOI : 10.1103/PhysRevLett.121.086805  Download: PDF  Cite : Bibtex RIS 
1  Author  Z. Z. Shao , Z. Z. Yin , H. Song , W. Liu , X. J. Li , J. Zhu , K. Biermann , L. L. Bonilla , H. T. Grahn , Y. H. Zhang 
Title 
Fast Detection of a Weak Signal by a Stochastic Resonance Induced by a Coherence Resonance in an Excitable GaAs/Al_{0.45}Ga_{0.55}As Superlattice 

Source  Phys. Rev. Lett. , 121 , 086806 ( 2018 )  
DOI : 10.1103/PhysRevLett.121.086806  Download: PDF  Cite : Bibtex RIS 