Detecting Weak Coupling of Quantum Systems with a Nonequilibrium Fano Resonance

Journal Article · Mon Apr 25 00:00:00 EDT 2016 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.93.165435· OSTI ID:1512879

Xiao, S. ^[1]; Yoon, Y. ^[1]; Lee, Y. -H. ^[1]; Bird, J. P. ^[2]; Ochiai, Y. ^[3]; Aoki, N. ^[3]; Reno, John L. ^[4]; Fraansson, J. ^[5]

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1. Univ. at Buffalo, the State Univ. of New York, Buffalo, NY (United States)
2. Univ. at Buffalo, the State Univ. of New York, Buffalo, NY (United States); Chiba Univ., Chiba (Japan)
3. Chiba Univ., Chiba (Japan)
4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
5. Uppsala Univ., Uppsala (Sweden)

A critical aspect of quantum mechanics is the nonlocal nature of the wavefunction, a characteristic that may yield unexpected coupling of nominally-isolated systems. The capacity to detect this coupling can be vital in many situations, especially those in which its strength is weak. In this work we address this problem in the context of mesoscopic physics, by implementing an electron-wave realization of a Fano interferometer using pairs of coupled quantum point contacts (QPCs). Within this scheme, the discrete level required for a Fano resonance is provided by pinching off one of the QPCs, thereby inducing the formation of a quasi-bound state at the center of its self-consistent potential barrier. Using this system, we demonstrate a form of $$\textit{nonequilibrium}$$ Fano resonance (NEFR), in which nonlinear electrical biasing of the interferometer gives rise to pronounced distortions of its Fano resonance. Our experimental results are captured well by a quantitative theoretical model, which considers a system in which a standard two-path Fano interferometer is coupled to an additional, $$\textit{intruder}$$, continuum. According to this theory, the observed distortions in the Fano resonance arise $$\textit{only}$$ in the presence of coupling to the intruder, indicating that the NEFR provides a sensitive means to infer the presence of weak coupling between mesoscopic systems.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000; FG02-04ER46180
• OSTI ID: 1512879
• Alternate ID(s): OSTI ID: 1249724
• Report Number(s): SAND-2015-9047J; PRBMDO; 664884
• Journal Information: Physical Review B, Vol. 93, Issue 16; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

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