By combining optical spin orientation and an externally applied longitudinal electric field, transverse charge accumulation has been detected in very high mobility two-dimensional hole gases by measuring the transverse voltage drop across simple Hall devices. Our results indicate intrinsic band-structure (rather than extrinsic skew scattering) derived spin-orbit coupling as the underlying mechanism of this spin-polarised transport effect. PACS numbers: 71.70.Ej, 72.25.Dc, 72.25.Fe, 78.55.Cr,

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... 20.My, 78.67.De Recent years have seen a profusion of spin-polarised transport phenomena: The spin Hall effect (SHE) [1-4], anomalous Hall effect (AHE) [5], the inverse spin Hall effect (ISHE) [6], the spin-injection Hall effect (SIHE) [7], the spin galvanic effect [8] and the circular photogalvanic effect (CPGE) [9] . Such spintronic effects are of immense interest for quantum computing due to potential spintronic devices having faster switching times and lower power consumption than conventional electronic ones. All of these above spintronic effects rely on the spin-orbit interaction (SOI) to bend the trajectories of spin-up and spin-down charge carriers in opposite directions. The spin-Hall conductivity thus arises as a result of the spin-orbit (SO) coupling, which can either be intrinsic to the band structure (Dresselhaus or Rashba), or alternatively, extrinsic in origin; deriving from asymmetric impurity scattering for up and down spins (skew scattering). There have been a number of reports of measurements, in both non-magnetic semiconductors and metals, where the mechanism has been clearly extrinsic [2, 4, 6, 7] . There have been very few claims, on the other hand, of measurements of a spin-Hall conductivity, in non-magnetic semiconductors, whose mechanism is intrinsic [3, 10]. Although in Ref. [3] the authors state that theoretically the intrinsic mechanism might apply, they provide no experimental evidence and indeed their two-dimensional (2D) hole system is of very low mobility (µ = 3400 cm 2 /V s). Similarly in Ref. [10] the authors only speculate that it is more likely that their measurements of the photoinduced AHE of excitons in unstrained, undoped GaAs quantum wells at room temperature have an intrinsic origin, with no indication of the quality of their quantum wells given. Thus definitive detection of an intrinsic spin-polarised transport effect still remains elusive. Theoretical consensus is now that the intrinsic contribution is more likely to exist in p-type material and that it vanishes for n-type [11] . In inversion symmetric systems, the SHE, the AHE and the ISHE (and thus the SIHE) are essentially the same phenomenon and there are established relations between them [12] . The drawback of the SHE [1-3] is that, due to the charge-balanced nature of its spin currents, electrical detection is impossible. In the AHE [5], on the other hand, the imbalance in the numbers of spin-up and spin-down carriers ensures that its transverse spin current generates a measurable transverse charge current or voltage. The AHE has traditionally been observed in ferromagnets and dilute magnetic semiconductors [5] . In non-ferromagnetic materials, such as, for instance, non-magnetic semiconductors, such a spin imbalance can either be