Magneto-structural phase transitions and two-dimensional spin waves in graphite

We have previously found experimental evidence for several quantum phenomena in oxygen-ion implanted of hydrogenated graphite: ferromagnetism, antiferromagnetism, paramagentism, triplet superconductivity, Andreev states, Little-Parks oscillations, Lamb shift, Casimir effect, colossal magnetoresistance, and topologically-protected flat-energy bands [1-6]. Triplet superconductivity results in the formation of Josephson junctions, thus with potential of being used for spintronics applications in the critical area of quantum computing. In this paper, we are showing new experimental evidence for the formation of two-dimensional (2D) spin waves in oxygen-ion enriched and in hydrogenated highly oriented pyrolytic graphite. The temperature evolution of the remanent magnetization Mrem(T) data confirms the formation of spin waves that follow the 2D Heisenberg model with a weak uniaxial anisotropy. In addition, the step-like features also found in the temperature dependence of the electrical resistivity between insulating and metallic states suggest several outstanding possibilities, such as a structural transition, triplet superconductivity, and chiral properties.Comment: 8 pages,7 figures, accepted by the Conference Editors for the CEC-ICMC 2023 Conference for publication in the IOP Conference Series: Materials Science and Engineering, Advances in Cryogenic Engineerin

Flat-band energy analysis of the temperature-dependent superconducting gap for hydrogenated graphite fibers found from nonlocal electrical conductance experimental data

Experimental evidence of novel phenomena in hydrogenated graphite fibers is found. An indirect excitonic mechanism is likely leading to a SC state below the temperature Tc = 50 K, where the gap is divergent. Analysis of the gap within the framework provided by the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity shows that this is a multigap system. The energy gap data can be better explained within the framework of topologically protected flat bands applied to systems in which superconductivity occurs on the surface or at the internal interfaces of the samples. The temperature dependence of the SC gap is linear above 50 K. We use nonlocal differential conductance Gdiff(V) = dI(V)/dV experimental data to show clear evidence of topological phenomena such as interference of chiral asymmetric Andreev edge states and crossed Andreev conversion. Gdiff(V) has a negative part that results from the nonlocal coherence between electron and holes in the Andreev edge states. We conclude that hydrogenated graphite bears the marks of an unconventional high-temperature superconductor (HTSC).Comment: 5 pages, 7 figures. arXiv admin note: substantial text overlap with arXiv:2005.0587

Patterned Field Induced Polymer Walls for Smectic a Bistable Flexible Displays

We have obtained a polymer wall-stabilized smectic A liquid crystal to be used for bistable flexible displays. The polymer wall structure optimally connects the two substrates together, thus providing maximum flexibility as compared to the polymer dispersed liquid crystal. Moreover, all the intrinsic bistable properties of the smectic A material are preserved. We analyzed the pixel performance and demonstrated very good electro-optical characteristics, high contrast ratio, and excellent stability of the states. The polymer wall-stabilized smectic A on flexible substrates has high potential to be used as electronic paper.</p

Field-Induced Polymer Wall Formation in a Bistable Smectic-A Liquid Crystal Display

We developed a composite system to produce robust bistable smectic-A (SmA) liquid crystal based flexible displays by encapsulating the liquid crystal material in a polymer wall structure. While keeping all the intrinsic bistable properties of the SmA material, the field-induced polymer walls bridge the two display substrates and bring significant advantages over the polymer dispersed liquid crystal structure. Here we analyze the performance of an encapsulated pixel and demonstrate superior electro-optical characteristics, high contrast ratio, and excellent sunlight readability. (c) 2006 American Institute of Physics.</p