RESUMEN
In 2005, Kane and Mele [Phys. Rev. Lett. 95, 226801 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.226801] predicted that at sufficiently low energy, graphene exhibits a topological state of matter with an energy gap generated by the atomic spin-orbit interaction. However, this intrinsic gap has not been measured to this date. In this Letter, we exploit the chirality of the low-energy states to resolve this gap. We probe the spin states experimentally by employing low temperature microwave excitation in a resistively detected electron-spin resonance on graphene. The structure of the topological bands is reflected in our transport experiments, where our numerical models allow us to identify the resonance signatures. We determine the intrinsic spin-orbit bulk gap to be exactly 42.2 µeV. Electron-spin resonance experiments can reveal the competition between the intrinsic spin-orbit coupling and classical Zeeman energy that arises at low magnetic fields and demonstrate that graphene remains to be a material with surprising properties.
RESUMEN
The precise value of the g factor in graphene is of fundamental interest for all spin-related properties and their application. We investigate monolayer graphene on a Si/SiO_{2} substrate by resistively detected electron spin resonance. Surprisingly, the magnetic moment and corresponding g factor of 1.952±0.002 is insensitive to charge carrier type, concentration, and mobility.
RESUMEN
Fifty consecutive patients (mean age 56 years) were examined to evaluate the reliability of transesophageal echocardiography in the evaluation of the left proximal coronary artery. Results of 28 cases were compared to selective coronary angiography. Echocardiography was able to visualize the left main artery for the length of 1.0 +/- 0.6 cm in all patients (100%), the left circumflex artery for maximal 3.1 +/- 1.4 cm in 86% and the left anterior descending artery as long as 2.3 +/- 0.9 cm in 58%. The intraluminal diameter of the most proximal localized segments measured by echocardiography and angiography in the LAO and RAO-projection was in terms of the left main artery 4.1 +/- 0.9 mm, 4.1 +/- 0.9 mm and 4.0 +/- 0.9 mm (n.s.), of the left circumflex artery 2.8 +/- 0.5 mm, 3.3 +/- 0.8 mm and 3.3 +/- 0.9 mm (n.s.) and of the left anterior descending artery 3.0 +/- 0.8 mm, 3.4 +/- 0.7 mm, and 3.6 +/- 1.0 mm (n.s.). In respect of detection of coronary artery stenoses in correspondence to the coronary angiogram sensitivity was 81%, specificity 93% and positive predictive accuracy 86%. Quantitative analyses of the coronary anatomy and the correlation to angiography could contribute to the validation of transoesophageal echocardiography.