Sowmya Somanchi wins the 2015 „Falling Walls Lab Jülich“ competition. Under the slogan "Great Minds - 3 Minutes - 1 Day" 15 young scientsits did their best to convince the jury by a 3 minunts talk on their own research topic. Sowmya is now invited to the "Falling Walls Conference" on the 8th und 9th November in Berlin.

For more information please see: Pressemitteilung Forschungszentrum Jülich.

Alexander Braun (1.v.l.), Sowmya Somanchi (2.v.l.) und Moritz Nabel (rechts) fahren zum Finale und zur "Falling Walls Conference" nach Berlin. Prof. Wolfgang Marquardt (2.v.r.), Vorstandsvorsitzender des Forschungszentrums, war Mitglied der Jury des ersten "Falling Walls Lab Jülich". Copyright: Forschungszentrum Jülich.

Phys. Rev. B 92, 085417 (2015)
Freestanding Bi₂Se₃ single-crystal flakes of variable thicknesses are grown using a catalyst-free vapor-solid synthesis and are subsequently transferred onto a clean Si⁺⁺/SiO₂ substrate where the flakes are contacted in Hall bar geometry. Low-temperature magnetoresistance measurements are presented which show a linear magnetoresistance for high magnetic fields and weak antilocalization (WAL) at low fields. Despite an overall strong charge-carrier tunability for thinner devices, we find that electron transport is dominated by bulk contributions for all devices. Phase-coherence lengths l_ϕ as extracted from WAL measurements increase linearly with increasing electron density exceeding 1μm at 1.7 K. Although l_ϕ is in qualitative agreement with electron-electron interaction-induced dephasing, we find that spin-flip scattering processes limit l_ϕ at low temperatures.

Phys. Rev. B 92, 075417(2015)
We present a numerical study on the uniformity of the pseudomagnetic field in graphene as a function of the relative orientation between the graphene lattice and straining directions. We calculated the deformation of a regular micron-sized graphene hexagon by symmetrically displacing three of its edges. We found that the pseudomagnetic field is strongest if the strain is applied perpendicular to the armchair direction of graphene. For a hexagon with a side length of 1μm, the pseudomagnetic field has a maximum of 1.2 T for an applied strain of 3.5% and it is uniform (variance <1%) within a circle with a diameter of ∼520 nm. This diameter is on the order of the typical diameter of the laser spot in a state-of-the-art confocal Raman spectroscopy setup, which suggests that observing the pseudomagnetic field in measurements of shifted magnetophonon resonance is feasible.

Science Advances 1, e1500222 (2015)
Graphene research has prospered impressively in the past few years, and promising applications such as highfrequency transistors, magnetic field sensors, and flexible optoelectronics are just waiting for a scalable and costefficient fabrication technology to produce high-mobility graphene. Although significant progress has been made in chemical vapor deposition (CVD) and epitaxial growth of graphene, the carrier mobility obtained with these techniques is still significantly lower than what is achieved using exfoliated graphene. We show that the quality of CVD-grown graphene depends critically on the used transfer process, and we report on an advanced transfer technique that allows both reusing the copper substrate of the CVD growth and making devices with mobilities as high as 350,000 cm² V^–1 s^–1, thus rivaling exfoliated graphene.

2D Mater. 2, 030202 (2015)
We review current challenges and perspectives in graphene spintronics, which is one of the most promising directions of innovation, given its room-temperature long-spin lifetimes and the ability of graphene to be easily interfaced with other classes of materials (ferromagnets, magnetic insulators, semiconductors, oxides, etc.), allowing proximity effects to be harvested. The general context of spintronics is first discussed together with open issues and recent advances achieved by the Graphene Spintronics Work Package consortium within the Graphene Flagship project. Based on such progress, which establishes the state of the art, several novel opportunities for spin manipulation such as the generation of pure spin current (through spin Hall effect) and the control of magnetization through the spin torque phenomena appear on the horizon. Practical applications are within reach, but will require the demonstration of wafer-scale graphene device integration, and the realization of functional prototypes employed for determined applications such as magnetic sensors or nano-oscillators. This is a specially commissioned editorial from the Graphene Flagship Work Package on Spintronics. This editorial is part of the 2D materials focus collection on ‘Progress on the science and applications of two dimensional materials,’ published in association with the Graphene Flagship. It provides an overview of key recent advances of the spintronics work package as well as the mid-term objectives of the consortium.