The temperature dependence of the mobility in suspended graphene samples is investigated. In clean samples, flexural phonons become the leading scattering mechanism at temperature T 10 K, and the resistivity increases quadratically with T . Flexural phonons limit the intrinsic mobility down to a few m 2 /Vs at room T . Their effect can be eliminated by applying strain or placing graphene on a substrate.Introduction.-The properties of isolated graphene continue to attract enormous interest due to both its exotic electronic properties [1] and realistic prospects of various applications [2]. It has been found that the intrinsic mobility µ of charge carriers in graphene can exceed 20 m 2 /Vs at room temperature T [3, 4], which is the absolute record. So far, such high values have not been achieved experimentally, because extrinsic scatterers limit µ. The highest µ was reported in suspended devices [5,6] and could reach ∼ 12 m 2 /Vs at 240 K [7]. This however disagrees with the data of Ref. [5] where similar samples exhibited room T µ close to ∼ 1 m 2 /Vs, the value that is routinely achievable for graphene on a substrate.

√s NN = 5.02 TeV using the ALICE detector at the LHC. The measurement covers the p T interval 0.5 < p T < 12 GeV/c and the rapidity range −1.065 < y cms < 0.135 in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor R pPb was calculated by comparing the p T -differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at √ s = 2.76 TeV and √ s = 7 TeV. The R pPb is consistent with unity within uncertainties of about 25%, which become larger for p T below 1 GeV/c. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-p T yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects. IntroductionThe Quark-Gluon Plasma (QGP) [1,2], a colour-deconfined state of strongly-interacting matter, is predicted to exist at high temperature according to lattice Quantum Chromodynamics (QCD) calculations [3]. These conditions can be reached in ultra-relativistic heavy-ion collisions [4][5][6][7][8][9][10]. Charm and beauty (heavy-flavour) quarks are mostly produced in initial hard scattering processes on a very short time scale, shorter than the formation time of the QGP medium [11], and thus experience the full temporal and spatial evolution of the collision. While interacting with the QGP medium, heavy quarks lose energy via elastic and radiative processes [12][13][14]. Heavy-flavour hadrons are therefore well-suited probes to study the properties of the QGP. The effect of energy loss on heavy-flavour production can be characterised via the nuclear modification factor (R AA ) of heavy-flavour hadrons. The R AA is defined as the ratio of the heavy-flavour hadron yield in nucleusnucleus (A-A) collisions to that in proton-proton (pp) collisions scaled by the average number of binary nucleon-nucleon collisions. The R AA is studied differentially as a function of transverse momentum (p T ), rapidity ( y) and collision centrality. It was measured at the Relativistic Heavy Ion Collider (RHIC) [15][16][17][18] and at the Large Hadron Collider (LHC) [19][20][21][22]. At RHIC, in central The interpretation of the measurements in A-A collisions requires the study of heavy-flavour production in p-A collisions, which provides access to cold nuclear matter (CNM) effects. These effects are not related to the formation of a colour-deconfined medium, but are present in case of colliding nuclei (or protonnucleus). An important CNM effect in the initial state is partondensity shadowing or saturation, which can be described using modified parton distribution functions (PDF) in the nucleus [23] or using the Color Glass Condensate (CGC) effective theory [24]. Further CNM effects include energy loss [25] in...

After the first unequivocal demonstration of spin transport in graphene, surprisingly working at room temperature (Tombros et al., 2007), it was quickly realised the relevance of this then recently discovered material, for both fundamental spintronics and future applications. Over the last decade, exciting results have made the field of graphene spintronics to blossom and evolve to a next generation of studies extending to new two-dimensional (2D) compounds. This Colloquium reviews recent theoretical and experimental advances in studies of electronic spin transport in graphene and related 2D materials, focusing on the new perspectives provided by heterostructures thereof and their emergent phenomena, including proximity-enabled spin-orbit effects, coupling spin to light, electrical tunability and 2D magnetism. We conclude by listing current challenges and promising research directions.

We study a spin Hamiltonian for spin-orbit-coupled ferromagnets on the honeycomb lattice. At sufficiently low temperatures supporting the ordered phase, the effective Hamiltonian for magnons, the quanta of spin-wave excitations, is shown to be equivalent to the Haldane model for electrons, which indicates the nontrivial topology of the band and the existence of the associated edge state. At high temperatures comparable to the ferromagnetic-exchange strength, we take the Schwingerboson representation of spins, in which the mean-field spinon band forms a bosonic counterpart of the Kane-Mele model. The nontrivial geometry of the spinon band can be inferred by detecting the spin Nernst effect. A feasible experimental realization of the spin Hamiltonian is proposed. Introduction.-Electronic systems with spin-orbit coupling (SOC) can exhibit spin Hall effects, in which a longitudinal electric field generates a transverse spin current and vice versa [1]. In particular, Kane and Mele [2] showed that a single layer of graphene has a topologically nontrivial band structure with an SOC-induced energy gap, which gives rise to a quantum spin Hall effect characterized by helical edge states. This identification of graphene as a quantum spin Hall insulator has served as a starting point for the search for other topological insulators [3,4].

The electronic band structure of a material can acquire interesting topological properties in the presence of a magnetic field or as a result of the spin-orbit coupling [1][2][3] . We study graphene on Ir, with Pb monolayer islands intercalated between the graphene sheet and the Ir surface. Although the graphene layer is structurally una ected by the presence of the Pb islands, its electronic properties change markedly, with regularly spaced resonances appearing. We interpret these resonances as the e ect of a strong and spatially modulated spin-orbit coupling, induced in graphene by the Pb monolayer. As well as confined electronic states, the electronic spectrum has a series of gaps with non-trivial topological properties, resembling a realization of the quantum spin Hall e ect proposed by Bernevig and Zhang 4