Skyrmion-Topological insulator and Weyl semimetal technology

Project Information

SKYTOP

Grant agreement ID: 824123

DOI

10.3030/824123

Project closed

EC signature date 23 October 2018

Start date 1 November 2018

End date 30 April 2023

Funded under

• EXCELLENT SCIENCE - Future and Emerging Technologies (FET)

Total cost

€ 4 508 487,50

EU contribution

€ 4 508 487,50

Coordinated by

"NATIONAL CENTER FOR SCIENTIFIC RESEARCH ""DEMOKRITOS"""
Greece

Periodic Reporting for period 3 - SKYTOP (Skyrmion-Topological insulator and Weyl semimetal technology)

Reporting period: 2021-11-01 to 2023-04-30

Summary of the context and overall objectives of the project

SKYTOP-Skyrmion-topological insulator and Weyl semimetal technology
SKYTOP develops a technology based on topological quantum matter that can have an impact on information processing and storage. The project gathers expertise from Greece, France, Germany, Italy and Belgium to face challenges in materials growth, device modelling and evaluation as well as scale-up of the technology for future volume production.

Magnetic materials show unusual swirling configurations of their spin (Skyrmions) characterized by non-trivial topology, while a class of topological materials known as topological insulators (TI) and Weyl semimetals (WSM) show unexpected transport properties due to unusual twisting of their electronic band structure. In SKYTOP we aim to combine these different classes of topological matter and demonstrate that they can lead to new energy efficient ways of manipulating and storing bits of information. It will be a big challenge in this project to show that possible compatibility issues can be overcome and that the new topological materials combinations can be synergetic and fully functional.

The overall objectives of the project are:
• Explore synergies between two classes of topological materials: Skyrmions (topology in real space) and topological Insulators (TI) and Weyl semimetals (topology in reciprocal space). The ultimate goal is to enable low power all-electric skyrmion manipulation for magnetic and spintronic devices.
• Open an exploitation route for Weyls (and TIs) for practical applications. The Spin Hall effect is a key property for Weyls (and TIs) that could lead to important applications if combined with magnetic materials such as Skyrmionic materials. Large area growth by a variety of synthetic thin film growth techniques (MBE, MOCVD, sputtering) as well as a growth scale-up activity are key for the development of manufacturable topological devices in the future.
• Mobilize the emerging community on topological matter. An aggressive outreach activity is envisaged to increase awareness in a wider scientific and technological society about the opportunities offered by topological materials.


Expected impacts on society
Our new skyrmionic magnetic devices, enhanced by TI and WSM materials, offer ultra-low power consumption, and enable the design of next generation neuromorphic devices and circuits with expected impact on artificial intelligence (AI) of the future. AI is expected to penetrate every part of our daily lives at home and work, improving services and security and enhancing the well-being of citizens by enabling for example autonomous driving and health monitoring and prevention.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the past 36 months, SKYTOP partners first developed topological Insulators and Weyl Semimetals separately, selecting the best candidates for further development and device realization. Then, the consortium put materials from different classes together in the same heterostructure (e.g. magnetic/TI, magnetic/Weyl) to make progress towards all electrical skyrmion manipulation which is the main goal. More specifically, the consortium successfully demonstrated that:
- materials from different classes can “live” together without adversely affecting the physical properties of one another. More specifically, the target was to find out whether magnetic materials can leave in tact the topological surface states of TIs and Weyl semimetals.
-The topological materials (TIs and Weyls) have a beneficial effect on charge-spin interconversion so that they can be used efficiently in spintronics devices.

During the last 18 months until the end of the project, the consortium claims three main achievements:
1. SKYTOP has produced the first generation of a skyrmion-based neuromorphic device which could form the basic unit of a larger Artificial Neural Network in hardware. The basic unit emulates the function of synaptic input currents to an artificial neuron voltage output, taking advantage of the anomalous Hall effect. This device is based on conventional, mature materials combinations which operate at room temperature. A patent application has been submitted by two consortium members as co-owners of the results.
2. SKYTOP has prepared the second generation of a skyrmion based neuromorphic device which is based on novel materials combinations developed within SKYTOP project. These novel combinations consist of topological insulator/2D van der Waals ferromagnet heterostructures. The consortium has showed indirect evidence of the presence of skyrmions via the the topological Hall effect at low temperature and has proven that certain materials combinations can operate well above room temperature. Moreover, the consortium has shown that all-electrical magnetization switching is possible in the TI/2D ferromagnet system which is a key property for the manipulation of skyrmions to realize the neuromorphic device.
3. SKYTOP has successfully assessed the scale-up of growth of the TIs on large area wafers up to 200 mm which the first important step towards manufacturable devices and volume production of the second generation of neuromorphic devices in the future.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Several results are at-or beyond- the state of the art:
(a) The neuromorphic device uses a large number of countable skyrmions which improves the signal to noise ratio with respect to rival devices. In addition, our device comprises a gate field-tunable synaptic weight as a result of the modulation of the magnetic anisotropy, which is a unique feature.
(b) the skyrmion detection in epitaxially grown 2D ferromagnet CrTe2 in an indirect way via the topological Hall effect is at the state of the art. The only direct observation of skyrmions by Lorenz microscopy has been made on exfoliated flakes in this material.
(c) SKYTOP has achieved record high Curie temperature of 570K in the 2D ferromagnet Fe5-xGeTe2/ Bi2Te3 Topological Insulator heterostructure, which creates prospects that the second generation of neuromorphic devices will employ advanced materials combinations based on topological insulators and 2D ferromagnets with improved performance at room temperature.

The project has made significant contributions first in the scientific domain unveiling the physical properties of new skyrmion materials, especially those classified as 2D ferromagnets, second by scaling up the technology to large area Si substrates with the aim to commercialize new functional devices made of composite skyrmion /Sb2Te3 or Bi2Te3 topological insulator layers, third by fabricating skyrmion synapses and neurons to realize skyrmion artificial neural networks (ANN) in hardware. It is envisaged that our work on skyrmion ANNs will impact neuromorphic computing with great benefits in processing big inhomogeneous data with much improved energy efficiency. Applications are foreseen in the area of edge intelligence enforcing security since data can be processed at the edge, avoiding the more vulnerable cloud.

Skyrmions in antiferromagnetic layers (left).Surface states in a topological insulator (right)

Skyrmion-based synapse