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- Bray, C., et al.
(författare)
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Temperature-dependent zero-field splittings in graphene
- 2022
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 106:24
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Tidskriftsartikel (refereegranskat)abstract
- Graphene is a quantum spin Hall insulator with a 45μeV-wide nontrivial topological gap induced by the intrinsic spin-orbit coupling. Even though this zero-field spin splitting is weak, it makes graphene an attractive candidate for applications in quantum technologies, given the resulting long spin-relaxation time. On the other side, the staggered sublattice potential, resulting from the coupling of graphene with its boron nitride substrate, compensates intrinsic spin-orbit coupling and decreases the nontrivial topological gap, which may lead to the phase transition into trivial band insulator state. In this work, we present extensive experimental studies of the zero-field splittings in monolayer and bilayer graphene in a temperature range 2-12 K by means of subterahertz photoconductivity-based electron spin-resonance technique. Surprisingly, we observe a decrease of the spin splittings with increasing temperature. We discuss the origin of this phenomenon by considering possible physical mechanisms likely to induce a temperature dependence of the spin-orbit coupling. These include the difference in the expansion coefficients between the graphene and the boron nitride substrate or the metal contacts, the electron-phonon interactions, and the presence of a magnetic order at low temperature. Our experimental observation expands knowledge about the nontrivial topological gap in graphene.
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| 4. |
- Sachs, J., et al.
(författare)
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Migration of existing access networks towards multi-radio access
- 2006
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Ingår i: IEEE Veh Technol Conf. - 1424400635 - 9781424400638 ; , s. 2987-2991
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Konferensbidrag (refereegranskat)abstract
- Integration of heterogeneous access technologies to provide multi-radio access allows for dynamic access selection. The "always best connected" paradigm can increase system capacity and end user throughput, as well as, reduce the network deployment costs for multi-radio wireless networks. In this paper we present the functional entities Generic Link Layer and Multi-Radio Resource Management, and describe their interactions for access selection. A focus of the paper is to show - with an example given for 3G and WLAN - how existing wireless networks can be migrated to provide multi-radio access functionality. This will be explained for a single operator integrating different radio access standards, as well as, for multiple cooperating network operators.
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| 7. |
- Gebert, Florian, et al.
(författare)
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An electrochemical evaluation of state-of-the-art non-flammable liquid electrolytes for high-voltage lithium-ion batteries
- 2023
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 556
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Tidskriftsartikel (refereegranskat)abstract
- The rapid and accelerating adoption of lithium-ion batteries worldwide, especially in the transportation sector, has focused attention on their safety. One area of particular interest is finding alternatives for their most flammable component, the liquid electrolyte. Over the past 20 years, a number of non-flammable liquid elec-trolytes have been identified and tested. However, because these data are frequently obtained under a wide range of conditions - e.g., different active materials, current densities or voltage cutoffs - it is difficult to compare them. In this work, eight promising non-flammable liquid electrolytes - four phosphate derivatives and four based on fluorinated hydrocarbons - are identified from the literature and tested in commercially relevant high -voltage systems under identical conditions. The electrochemical stabilities of the electrolytes were studied against both inert electrodes and in LiNi0.6Mn0.2Co0.2O2|graphite cells. Each electrolyte was assessed via long-term cycling experiments and rate-testing and the cell resistance during aging was monitored. It was found that the electrolytes containing phosphate and phosphonate-based solvents generally performed very poorly compared to the phosphorus-free fluorinated solvents; the latter resulted, on average, in twice the capacity retention after 500 cycles of the former. A strong correlation was observed between long-term cycling perfor-mance, rate capability and the cell resistance.
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| 8. |
- Jayamani, Jayaraj, et al.
(författare)
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Nano-porous surface states of Ti–Y–Al–Co phase separated metallic glass
- 2009
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Ingår i: Intermetallics (Barking). - : Elsevier BV. - 0966-9795 .- 1879-0216. ; 17:12, s. 1120-1123
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Tidskriftsartikel (refereegranskat)abstract
- A novel nano-porous state was fabricated at the surface of the Ti-based metallic glass by selective etching technique. By transforming the surface of the Ti45Y11Al24Co20 phase separated alloy from smooth towards rough with nano-pores in an oxidised state, the passivation behaviour of the glassy alloy in simulated body fluid condition was remarkably improved leading to corrosion resistance significantly higher than that of the Ti–6Al–4V alloy, one of the favourite candidate materials for implant applications.
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