Recently, a research team led by Prof. Dr. YANG Yong from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) revealed remarkable quantum tunneling phenomenon across double potential barriers. They found that quantum tunneling dominant at low temperatures and continues to play a nontrivial role at temperatures up to ～600 K.
"This is an important progress in the dynamics of quantum particles across double barriers, which opens a possible avenue for ultrahigh precision measurement based on atomic systems," said Prof. YANG.
The results were published in Physical Review Research.
Is the real space infinitely divisible? In a macroscopic world the answer is definitely "Yes" since everyday experiences, such as the observations of water flows or the free-falling objects always give the impression of continuous trajectories. The situation changes dramatically in a quantum world. In theories trying to unify quantum mechanics with gravity, a minimum length is predicted to exist and generally taken to be the Planck length (lP), which is ~ 10-35 m.
In this work, researcher studies the quantum tunneling across double barriers and obtains a theorem which shows that, if the separation between two barriers can change continuously, i.e., the real space is a continuum, the incident particle can completely penetrate arbitrarily large double barriers by simply tuning the barrier-barrier separation.
This phenomenon is called resonant tunneling (RT). Otherwise, if a nonzero minimum length does exist, resonant tunneling stops when the barrier height exceeds a certain value. Theoretical analyses show that, the RT probability of quantum particles depends critically on the separation between two barriers.
"This work reveals the deep connection between quantum tunneling and the quantum theories for gravity, and opens a possible avenue for ultrahigh precision measurement and therefore testing the existence of a minimum length," said Prof. YANG.
Schematics of quantum tunneling across single barrier (upper panel) and double barriers (lower panel) at the presence of RT, where the inter-barrier spacing wn varies with a step of not smaller than the Planck length. (Image by YANG Yong)