Abstract
The higher the energy of a particle is above equilibrium, the faster it relaxes because of the growing phase space of available electronic states it can interact with. In the relaxation process, phase coherence is lost, thus limiting high-energy quantum control and manipulation. In one-dimensional systems, high relaxation rates are expected to destabilize electronic quasiparticles. Here, we show that the decoherence induced by relaxation of hot electrons in one-dimensional semiconducting nanowires evolves nonmonotonically with energy such that above a certain threshold hot electrons regain stability with increasing energy. We directly observe this phenomenon by visualizing, for the first time, the interference patterns of the quasi-one-dimensional electrons using scanning tunneling microscopy. We visualize the phase coherence length of the one-dimensional electrons, as well as their phase coherence time, captured by crystallographic Fabry-Pèrot resonators. A remarkable agreement with a theoretical model reveals that the nonmonotonic behavior is driven by the unique manner in which one-dimensional hot electrons interact with the cold electrons occupying the Fermi sea. This newly discovered relaxation profile suggests a high-energy regime for operating quantum applications that necessitate extended coherence or long thermalization times, and may stabilize electronic quasiparticles in one dimension.
9 More- Received 23 January 2017
- Corrected 22 May 2017
DOI:https://doi.org/10.1103/PhysRevX.7.021016
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
22 May 2017
Erratum
Publisher’s Note: Hot Electrons Regain Coherence in Semiconducting Nanowires [Phys. Rev. X 7, 021016 (2017)]
Jonathan Reiner, Abhay Kumar Nayak, Nurit Avraham, Andrew Norris, Binghai Yan, Ion Cosma Fulga, Jung-Hyun Kang, Torsten Karzig, Hadas Shtrikman, and Haim Beidenkopf
Phys. Rev. X 7, 029902 (2017)
Popular Summary
Semiconducting nanowires—wires with diameters measured in billionths of a meter—offer potential for use in many innovative applications, from flexible solar panels to miniaturized sensors. But not much is known about how electrons behave in these wires, which are thin enough for quantum effects to come into play, because nanowires are difficult to study. We constructed a “portable vacuum suitcase” that allows nanowires to be transferred intact from the chamber where they are grown to a scanning tunneling microscope, which allows us to perform the first exhaustive spectroscopic mapping of a semiconducting nanowire.
Using a scanning tunneling microscope, we observe interference patterns along the nanowire in order to study the evolution of electron phase coherence. Typically, electron phase coherence in mesoscopic solid-state materials depends on a low rate of scattering among electrons, and Landau’s principle tells us that the higher the energy of a hot electron, the faster it relaxes and therefore loses its phase coherence. We find that in semiconducting nanowires, where electrons are confined to one dimension, dispersion and Coulomb interaction interact in a way that revives phase coherence of ultrahot electrons; above a certain energy threshold, phase coherence grows with increasing energy.
These results are made possible by keeping the nanowires under ultrahigh vacuum at all times, from molecular beam epitaxy growth to subsequent measurement. This paves the way for further spectroscopic studies, such as spatial mapping of putative Majorana fermions—particles that are their own antiparticle—that might appear at the ends of nanowires once they become topologically superconducting.