Terahertz (THz) radiation has uses from security to medicine [1]; however, sensitive roomtemperature detection of THz is notoriously difficult [2]. The hot-electron photothermoelectric effect in graphene is a promising detection mechanism: photoexcited carriers rapidly thermalize due to strong electron-electron interactions [3,4], but lose energy to the lattice more slowly [3,5]. The electron temperature gradient drives electron diffusion, and asymmetry due to local gating [6,7] or dissimilar contact metals[8] produces a net current via the thermoelectric effect. Here we demonstrate a graphene thermoelectric THz photodetector with sensitivity exceeding 10 V/W (700 V/W) at room temperature and noise equivalent power less than 1100 pW/Hz 1/2 (20 pW/Hz 1/2 ), referenced to the incident (absorbed) power. This implies a performance which is competitive with the best room-temperature THz detectors [9] for an optimally coupled device, while time-resolved measurements indicate that our graphene detector is eight to nine orders of magnitude faster than those [7,10]. A simple model of the response, including contact asymmetries (resistance, work function and Fermi-energy pinning) reproduces the qualitative features of the data, and indicates that orders-of-magnitude sensitivity improvements are possible.Graphene has unique advantages for hot-electron photothermoelectric detection. Gapless graphene has strong interband absorption at all frequencies. The electronic heat capacity of single-layer graphene is much lower than in bulk materials, resulting in a larger change in temperature for the same absorbed energy. The photothermoelectric effect has a picosecond response time, set by the electronphonon relaxation rate. [10,11]. Hot electron effects have been exploited in graphene for sensitive bolometry in THz and millimeter-wave at cryogenic temperatures, by using temperature-dependent resistance in gapped bilayer graphene [12], which is sizable only at low temperature, or noise thermometry [13], which requires complex RF electronics. In contrast, our photothermoelectric approach is temperature insensitive and produces an observable dc signal even under room temperature conditions.To realize our graphene hot electron thermoelectric photodetector we generate an asymmetry by contacting graphene with dissimilar metals using a standard double-angle evaporation technique as shown in Figs. 1a-e (also see Methods). Fig. 1f shows optical and atomic-force micrographs of our monolayer graphene device. Two metal electrodes, each consisting of partially overlapping Cr and Au regions, contact the monolayer graphene flake. The 3 µm × 3 µm graphene channel is selected to be shorter than the estimated electron diffusion length [14]. Fig. 1g shows the schematic of our detector in cross section. Figs. 1h-k illustrate the principle of operation: Electrons in graphene are heated by the incident light and the contacts serve as a heat sink, resulting in a non-uniform electron temperature T(x)as a function of position x within the device (Fig. 1h)...

We present polarization-resolved transient transmission measurements on multi-layer black phosphorus.Background free two-color pump-probe spectroscopy measurements are carried out on mechanically exfoliated black phosphorus flakes that have been transferred to a large-bandgap, silicon carbide substrate. The blue-shifted pump pulse (780 nm) induces an increased transmission of the probe pulse (1560 nm) over a time scale commensurate with the measurement resolution (hundreds of fs). After the initial pump-induced transparency, the sign of the transient flips and a slower enhanced absorption is observed. This extended absorption is characterized by two relaxation time scales of 180 ps and 1.3 ns.The saturation peak is attributed to Pauli blocking while the extended absorption is ascribed to a Drude response of the pump-induced carriers. The anisotropic carrier mobility in the black phosphorus leads to different weights of the Drude absorption, depending on the probe polarization, which is readily observed in the amplitude of the pump-probe signals.

Among its many outstanding properties, graphene supports terahertz surface plasma wavessub-wavelength charge density oscillations connected with electromagnetic fields that are tightly localized near the surface [1, 2]. When these waves are confined to finite-sized graphene, plasmon resonances emerge that are characterized by alternating charge accumulation at the opposing edges of the graphene. The resonant frequency of such a structure depends on both the size and the surface charge density, and can be electrically tuned throughout the terahertz range by applying a gate voltage [3,4]. The promise of tunable graphene THz plasmonics has yet to be fulfilled, however, because most proposed optoelectronic devices including detectors, filters, and modulators [5][6][7][8][9][10] desire near total modulation of the absorption or transmission, and require electrical contacts to the graphene -constraints that are difficult to meet using existing plasmonic structures. We report here a new class of plasmon resonance that occurs in a hybrid graphene-metal structure.The sub-wavelength metal contacts form a capacitive grid for accumulating charge, while the narrow interleaved graphene channels, to first order, serves as a tunable inductive medium, thereby forming a structure that is resonantly-matched to an incident terahertz wave. We experimentally demonstrate resonant absorption near the theoretical maximum in readily-available, large-area graphene, ideal for THz detectors and tunable absorbers. We further predict that the use of high mobility graphene will allow resonant THz transmission near 100%, realizing a tunable THz filter or modulator. The structure is strongly coupled to incident THz radiation, and solves a fundamental problem of how to incorporate a tunable plasmonic channel into a device with electrical contacts. In order to be applied in practical optoelectronic devices, graphene terahertz plasmonic resonators must be connected to an antenna, transmission line, metamaterial, or other electrical contact, in order to sense or apply a voltage or current, or to improve the coupling to free-space radiation. The conductive boundary screens the electric field and inhibits the accumulation of charge density at the opposing edges of the graphene channel, thus disrupting the traditional graphene plasmon mode. Until now, there was no experimental evidence that two-dimensional plasmons could be confined with conductive boundaries.In this letter, we demonstrate a new type of plasmon resonance in metal-contacted graphene, and we use analytic calculations, numerical simulations, and THz reflection and transmission measurements to confirm the principle of operation. These plasmon modes shows strong coupling to incident terahertz radiation, so that maximal absorption in graphene can be achieved at a resonance frequency that is gate-tunable. We also introduce an equivalent circuit model that predicts the resonant frequency, linewidth, and impedance matching condition of the fundamental plasmon mode, and can be used for d...

Scienti¯c collaborations shape ideas as well as innovations and are both the substrate for, and the outcome of, academic careers. Recent studies show that gender inequality is still present in many scienti¯c practices ranging from hiring to peer-review processes and grant applications. In this work, we investigate gender-speci¯c di®erences in collaboration patterns of more than one million computer scientists over the course of 47 years. We explore how these patterns change over years and career ages and how they impact scienti¯c success. Our results highlight that successful male and female scientists reveal the same collaboration patterns: compared to scientists in the same career age, they tend to collaborate with more colleagues than other scientists, seek innovations as brokers and establish longer-lasting and more repetitive collaborations. However, women are on average less likely to adopt the collaboration patterns that are related with success, more likely to embed into ego networks devoid of structural holes, and they exhibit stronger gender homophily as well as a consistently higher dropout rate than men in all career ages.

Subwavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, subwavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a terahertz pump-terahertz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by 2 orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results. The model shows that the observed strong linearity is caused by an unexpected red shift of plasmon resonance together with a broadening and weakening of the resonance caused by the transient increase in electron temperature. The model further predicts that even greater resonant enhancement of the nonlinear response can be expected in high-mobility graphene, suggesting that nonlinear graphene plasmonic devices could be promising candidates for nonlinear optical processing.

We report a large area terahertz detector utilizing a tunable plasmonic resonance in subwavelength graphene microribbons on SiC(0001) to increase the absorption efficiency. By tailoring the orientation of the graphene ribbons with respect to an array of subwavelength bimetallic electrodes, we achieve a condition in which the plasmonic mode can be efficiently excited by an incident wave polarized perpendicular to the electrode array, while the resulting photothermal voltage can be observed between the outermost electrodes.

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In eukaryotes, the eukaryotic translation elongation factor eEF1A responsible for transporting amino-acylated tRNA to the ribosome forms a higher-order complex, eEF1H, with its guanine-nucleotide-exchange factor eEF1B. In metazoans, eEF1B consists of three subunits: eEF1B alpha, eEF1B eta and eEF1B gamma. The first two subunits possess the nucleotide-exchange activity, whereas the role of the last remains poorly defined. In mammals, two active tissue-specific isoforms of eEF1A have been identified. The reason for this pattern of differential expression is unknown. Several models on the basis of in vitro experiments have been proposed for the macromolecular organization of the eEF1H complex. However, these models differ in various aspects. This might be due to the difficulties of handling, particularly the eEF1B beta and eEF1B gamma subunits in vitro. Here, the human eEF1H complex is for the first time mapped using the yeast two-hybrid system, which is a powerful in vivo technique for analysing protein-protein interactions. The following complexes were observed: eEF1A1:eEF1B alpha, eEF1A1:eEF1B beta, eEF1B beta:eEF1B beta, eEF1B alpha:eEF1B gamma, eEF1B beta:eEF1B gamma and eEF1B alpha:eEF1B gamma:eEF1B beta, where the last was observed using a three-hybrid approach. Surprisingly, eEF1A2 showed no or only little affinity for the guanine-nucleotide-exchange factors. Truncated versions of the subunits of eEF1B were used to orientate these subunits within the resulting model. The model unit is a pentamer composed of two molecules of eEF1A, each interacting with either eEF1B alpha or eEF1B beta held together by eEF1B gamma. These units can dimerize via eEF1B beta. Our model is compared with other models, and structural as well as functional aspects of the model are discussed.