Condensed Matter and Materials Physics

Condensed matter and materials physics is the branch of physics that studies the properties of the large collections of atoms that compose both natural and synthetic materials.

This branch of physics has many practical applications and is currently producing many advances in fundamental physics.

Here is some of the research taking place at Loughborough University.

Members: Prof. Joseph Betouras, Prof. Feo Kusmartsev, Dr Ioannis Rousochatzakis

Theme:

The overarching goal of this research is the fundamental understanding of novel collective phases of matter, such as high-Tc superconductivity and quantum spin liquids, starting from microscopic principles and using modern analytical and computational quantum many-body methods.

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Members: Sergey Saveliev, Pavel Borisov, Alexander Balanov, Mike Cropper, Upul Wijayantha, Eran Fasil Dejene, Alexander Zagoskin, Eran Edirisinghe

Novel devices mimicking functionality of human neural systems – neuromorphic devices – is our hope to develop new technology allowing computer hardware to become as energy efficient as human brain when it comes to cognitive tasks of associative memory, recognition of visual images, words and features detection. Memristor is the fourth passive element in electric circuits in addition to three conventional ones (resistors, capacitors and inductors). Memristors change their resistance depending on electric pulse history. This allows, in principle, to fabricate artificial brains with artificial neurons linked via artificial synapses having an ability of learn and take actions based on information available.

Our group of researchers is working on modelling, fabrication, optimisation and testing of various neuromorphic memristor devices and artificial-neural networks based on different physical principles and computer architectures, in partnership with world-leading artificial intelligence companies and in collaboration with the Loughborough Departments of Chemistry and Computer Science, The University of Southampton, CNRS, Texas A&M University and other centres of neuromorphic research.

Fig caption: Sketch of future computer devices with the central “brain-like” part perform both memorising and processing information of stimulation provided via peripheral wire-like connections.

References

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Z Wang, S Joshi, SE Savel’ev, et al.,

Nature materials 16 (1), 101-108 (2017), link

Fully memristive neural networks for pattern classification with unsupervised learning

Z Wang, S Joshi, S Savel’ev et al.,

Nature Electronics 1 (2), 137-145 (2018), link

A novel true random number generator based on a stochastic diffusive memristor

H Jiang, D Belkin, SE Savel’ev et al., Nature communications 8, 882 (2017), link

Anatomy of Ag/Hafnia‐Based Selectors with 1010 Nonlinearity

Rivu Midya, Zhongrui Wang, Jiaming Zhang, Sergey E Savel'ev et al., Advanced Materials 29, 1604457 (2017), link

Quantized conductance coincides with state instability and excess noise in tantalum oxide memristors, W. Yi, S.E. Savel'Ev, G. Medeiros-Ribeiro et al., Nature Communications 7, 11142 (2016), link

Current grants:

EPSRC-standard (EP/S032843/1): Neuromorphic memristive circuits to simulate inhibitory and excitatory dynamics of neuron networks: from physiological similarities to deep learning

EPSRC=NIA (EP/T027479/1): Oxide Recurrent Neural Networks

Members: A. Balanov, B. Chesca, M. Greenaway, F. Kusmartsev, S. Saveliev

Fast electronic elements, such as semiconductor transistors, are key devices for many pivotal technologies from computing and communication to security, defence and medicine. Over the decades the speed of electronics has been growing dramatically and is now approaching the limit when conventional electronic elements are unable to progress further. To overcome this fundamental limit, we need to build devices based on the new physical principles. One of the research foci of the Department is the development of solid-state sub-THz and THz generators and detectors by utilising novel physical phenomena and materials.

Some recent papers:

Kusmartsev, F and Luo, Y (2020) Optical Transistor for Amplification of Radiation in a Broadband Terahertz Domain, Physical Review Letters, 124, 087701.

Wang, F, Poyser, C, Greenaway, M, Akimov, A, Campion, R, Kent, A, Fromhold, M, Balanov, A (2020) Ultrafast strain-induced charge transport in semiconductor superlattices, Physical Review Applied 14, 044037.

Chesca, B, John, D, Gaifullin, M, Cox, J, Murphy, A, Saveliev, S, Mellor, C (2020) Magnetic flux quantum periodicity of the frequency of the on-chip detectable electromagnetic radiation from superconducting flux-flow-oscillators, Applied Physics Letters, 117(14), 142601

Gaifullin, M, Alexeeva, NV, Hramov, AE, Makarov, VV, Maksimenko, VA, Koronovskii, AA, Greenaway, M, Fromhold, TM, Patane, A, Mellor, C, Kusmartsev, F, Balanov, A (2017) Microwave generation in synchronized semiconductor superlattices, Phys. Rev. Applied, 7, 044024

Gaskell, J, Eaves, L, Novoselov, KS, Mishchenko, A, Geim, AK, Fromhold, TM, Greenaway, MT (2015) Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators, Applied Physics Letters, 107(10), 103105

Two-dimensional (2D) materials are extremely thin, often only a single atom thick, crystalline layers.  They can be created by reducing a bulk (3D) layered material (for example graphite) to its individual atomic layers (graphene) by repeated exfoliation, for example by using sticky tape!  The properties of layered bulk materials are transformed and can exhibit exciting new physical phenomena when they are reduced to a single layer.  Graphene, the first 2D material to be isolated, is a single layer of carbon atoms with many exciting new properties.  For example: it is one of the strongest materials but very flexible; electrons in graphene behave as if they have no mass and as if they are moving at the speed of light; and it is a better conductor of electricity than copper.  The discovery of graphene’s potential led to the isolation and characterisation of many other 2D materials. Nearly 700 different types of 2D materials are predicted to exist each with very interesting properties for applications and now research in 2D materials graphene has attracted investment and research by many companies and universities around the world.

Here in the Physics department at Loughborough, our research activity on 2D materials is focused on understanding and developing their properties to create the next generation of novel magnetic, thermoelectric and electronic devices. We create new theories and models to understand how quantum physics can be used to control how electrical current flows through and between the layers of stacks of 2D materials. We investigate how interactions between electrons in these stacks can lead to new and exotic behaviour such as superconductivity at high temperatures. We are also fabricating and measuring heterostructures of 2D crystals for spintronic, thermoelectric and spin-caloritronic devices which take advantage of the intrinsic spin of electrons for low power, high frequency, logic and memory applications. We do our work in close collaboration with research groups across the world in the UK, US, Europe, Russia, China and Japan.

Members: Niladri Banerjee, Fasil Dejene, Kelly Morrison, Mark Greenaway

The rapid progress of electronics over the last hundred years – in particular with computing – has had a widespread impact on society. We have almost taken it for granted, that our phones and laptops will continue to have higher memory storage, work faster and have better battery life as we upgrade to the next version. Unfortunately, however, we are fast approaching a bottleneck in standard computing electronics: what is described as the end of ‘Moore’s Law’.

The area of spintronics (spin electronics) aims to utilise the quantum mechanical propertyies of an electron – its spin – to create functionalities and more efficiencies int devices that cannot be achieved by solely relying on the electron’s chargeelectronic devices for the next generation of computing. The discovery of spintronics was recognised by the 2007 Nobel Prize in Physics to Albert Fert and Peter Grunberg and have, over the last two decades, revolutionised data storage technology.

Our group of researchers isresearchers are working on nanospintronics, superconducting spintronics, and spin caloritronics, as welland spin caloritronics, as swith traditional thin films as well as with pin caloritronics, and the intersection of novel 2D and topological materials in this area. Our vision in this area is designing new types of functional materials and devices primary focus is on designing new types of devices for the generation and detection of spin currents, and establishing the condition under which these processes are energy efficient.

References:

Magnetic and structural properties of CoFeB thin films grown by pulsed laser deposition, G Awana, C Cox, L Stuffins, G Venkat, K Morrison, Z Zhou, D Backes, Materials Research Express 7, 106406 (2020)

Superconductivity-induced change in magnetic anisotropy in epitaxial ferromagnet-superconductor hybrids with spin-orbit interaction, C González-Ruano, LG Johnsen, D Caso, C Tiusan, M Hehn, N Banerjee, ..., Physical Review B 102, 020405 (2020)

Comparison between charge and spin transport in few-layer graphene, T Maasen, FK Dejene, MHD Guimarães, C Józsa and BJ van Wees, B. J., Phys. Rev. B 83, 115410 (2011).

Temperature dependence of the effective spin-mixing conductance probed with lateral non-local spin valves, KS Das, FK Dejene, BJ Van Wees, IJ Vera-Marun, Applied Physics Letters 114, 072405 (2019)

Anomalous Nernst effect in Co2MnSi thin films, CDW Cox, AJ Caruana, MD Cropper, K Morrison, Journal of Physics D: Applied Physics 53, 035005 (2019)

Thermopower and Unconventional Nernst Effect in the Predicted Type-II Weyl Semimetal WTe2, KG Rana, FK Dejene, N Kumar, CR Rajamathi, K Sklarek, C Felser, ..., Nano letters 18, 6591-6596 (2018)

Controlling the superconducting transition by spin-orbit coupling, N Banerjee, JA Ouassou, Y Zhu, NA Stelmashenko, J Linder, MG Blamire, Physical Review B 97, 184521 (2018)

Demonstration of polycrystalline thin film coatings on glass for spin Seebeck energy harvesting, AJ Caruana, MD Cropper, J Zipfel, Z Zhou, GD West, K Morrison, Physica status solidi (RRL)–Rapid Research Letters 10, 613-617 (2016)

Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves, FK Dejene, N Vlietstra, D Luc, X Waintal, JB Youssef, BJ Van Wees, Physical Review B 91, 100404 (2014)

Evidence for spin selectivity of triplet pairs in superconducting spin valves, N Banerjee, CB Smiet, RGJ Smits, A Ozaeta, FS Bergeret, MG Blamire, ..., Nature Communications 5, 1-6 (2014)

Current grants:

EPSRC Strategic Equipment (EP/W006243/1): Rapid Prototyping of Novel Devices with In-situ Deposition, Imaging and Nanolithography

EPSRC Fellowship (EP/P006221/1): Reliable, Scalable and Affordable Thermoelectrics: Spin Seebeck Based Devices for Energy Harvesting

EPSRC New Horizons (EP/V048767/1): Seeing magnons at spin-to-charge conversion interfaces

EPSRC NIA (EP/S016430/1): Spin-Orbit Coupling-Driven Superconducting Spintronics