Terahertz Spin-Conductance Spectroscopy: Probing Coherent and Incoherent Ultrafast Spin Tunneling.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38904438.
- Also identified by DOI 10.1021/acs.nanolett.4c00498 and PMC identifier 11229073.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Thin-film stacks <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi></math>|<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>H</mi></math> consisting of a ferromagnetic-metal layer <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi></math> and a heavy-metal layer <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>H</mi></math> are spintronic model systems. Here, we present a method to measure the ultrabroadband spin conductance across a layer <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>X</mi></math> between <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>F</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>H</mi></math> at terahertz frequencies, which are the natural frequencies of spin-transport dynamics. We apply our approach to MgO tunneling barriers with thickness <i>d</i> = 0-6 Å. In the time domain, the spin conductance <i>G</i><sub>s</sub> has two components. An instantaneous feature arises from processes like coherent spin tunneling. Remarkably, a longer-lived component is a hallmark of incoherent resonant spin tunneling mediated by MgO defect states, because its relaxation time grows monotonically with <i>d</i> to as much as 270 fs at <i>d</i> = 6.0 Å. Our results are in full agreement with an analytical model. They indicate that terahertz spin-conductance spectroscopy will yield new and relevant insights into ultrafast spin transport in a wide range of spintronic nanostructures.