Latest Papers in Condensed Matter Physics

Mesoscale And Nanoscale Physics

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Driving with temperature the synthesis of graphene films and nanoribbons on Ge(110) (1906.01571v1)

L. Persichetti, M. De Seta, A. M. Scaparro, V. Miseikis, A. Notargiacomo, A. Ruocco, A. Sgarlata, M. Fanfoni, F. Fabbri, C. Coletti, L. Di Gaspare

2019-06-04

By tuning the growth parameters, we show that it is possible to drive the CVD synthesis of graphene on Ge(110) towards the formation of either ultrathin armchair nanoribbons or of continuous graphene films. The ribbons are aligned along specific high-symmetry directions of the Ge(110) surface and have a width of ~5 nm. Moreover, by merging spectroscopic and morphological information, we find that the quality of graphene films depends critically on the growth temperature improving significantly in a narrow range close to the Ge melting point. The abruptness of the temperature behavior observed indicates that achieving high-quality graphene is intimately connected to the quasi-liquid Ge layer formed close to 930 {\deg}C on the substrate. Being observed for diverse Ge orientations, this process, known as incomplete melting, is shown to be of general relevance for graphene synthesis on Ge, and explains why similar growth conditions present in literature lead to graphene of very diverse quality on these substrates.

Thickness dependence of spin Peltier effect visualized by thermal imaging technique (1906.01560v1)

Shunsuke Daimon, Ken-ichi Uchida, Naomi Ujiie, Yasuyuki Hattori, Rei Tsuboi, Eiji Saitoh

2019-06-04

Magnon propagation length in a ferrimagnetic insulator yttrium-iron-garnet (YIG) has been investigated by measuring the YIG-thickness t_YIG dependence of the spin Peltier effect (SPE) in a Pt/YIG sample. We succeeded to measure the high-resolution t_YIG dependence of SPE by using the thermal imaging of SPE free from contamination by interference of infrared emissivity. Comparison between the experimental results and theoretical analyses demonstrates the existence of two propagation lengths for the magnon chemical potential and the magnon temperature.

Impact of Electrostatic Doping Level on the Dissipative Transport in Graphene Nanoribbons Tunnel Field-Effect Transistors (1905.06428v2)

Weixiang Zhang, Tarek Ragab, Ji Zhang, Cemal Basaran

2019-05-15

The impact of electrostatic doping level on the dissipative transport of Armchair GNR-TFET is studied using the Quantum Perturbation Theory (QPT) with the Extended Lowest Order Expansion (XLOE) implementation method. Results show that the doping level of the source and drain sides of the GNR-TFET has a significant impact on the phonon contribution to the carrier transport process. Unlike in other similar studies, where phonons are believed to have a constant detrimental influence on the ION/IOFF ratio and Subthreshold Swing (SS) of the TFET devices due to the phonon absorption-assisted tunneling, we show that by a proper engineering of the doping level in the source and drain, the phonon absorption assisted tunneling can be effectively inhibited. We also show that as temperature increase, the device switching property deteriorates in both the ballistic and dissipative transport regimes, and there exists a temperature-dependent critical doping level where the device has optimal switching behavior.

Resonance inversion in a superconducting cavity coupled to artificial atoms and a microwave background (1807.09567v3)

Juha Leppäkangas, Jan David Brehm, Ping Yang, Lingzhen Guo, Michael Marthaler, Alexey V. Ustinov, Martin Weides

2018-07-25

We demonstrate how heating of an environment can invert the line shape of a driven cavity. We consider a superconducting coplanar cavity coupled to multiple artificial atoms. The measured cavity transmission is characterized by Fano-type resonances with a shape that is continuously tunable by bias current through nearby (magnetic flux) control lines. In particular, the same dispersive shift of the microwave cavity can be observed as a peak or a dip. We find that this Fano-peak inversion is possible due to a tunable interference between a microwave transmission through a background, with reactive and dissipative properties, and through the cavity, affected by bias-current induced heating. The background transmission occurs due to crosstalk between the control and transmission lines. We show how such background can be accounted for by Jaynes-Cummings type models via modified boundary conditions between the cavity and transmission lines. We find generally that whereas resonance positions determine system energy levels, resonance shapes give information on system fluctuations and dissipation.

The -invariant and topological pathways to influence sub-micron strength and crystal plasticity (1906.01482v1)

Stefanos Papanikolaou, Giacomo Po

2019-06-04

In small volumes, sample dimensions are known to strongly influence mechanical behavior, especially strength and crystal plasticity. This correlation fades away at the so-called mesoscale, loosely defined at several micrometers in both experiments and simulations. However, this picture depends on the entanglement of the initial defect configuration. In this paper, we study the effect of sample dimensions with a full control on dislocation topology, through the use of a novel observable for dislocation ensembles, the -invariant, that depends only on mutual dislocation linking: It is built on the natural vortex character of dislocations and it has a continuum/discrete correspondence that may assist multiscale modeling descriptions. We investigate arbitrarily complex initial dislocation microstructures in sub-micron-sized pillars, using three-dimensional discrete dislocation dynamics simulations for finite volumes. We demonstrate how to engineer nanoscale dislocation ensembles that appear virtually independent from sample dimensions, either by biased-random dislocation loop deposition or by sequential mechanical loads of compression and torsion.

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