Spin-orbit coupling provides a versatile tool to generate and to manipulate the spin degree of freedom in low-dimensional semiconductor structures. The spin Hall effect, where an electrical current drives a transverse spin current and causes a nonequilibrium spin accumulation observed near the sample boundary, the spin-galvanic effect, where a nonequilibrium spin polarization drives an electric current, or the reverse process, in which an electrical current generates a nonequilibrium spin polarization, are all consequences of spin-orbit coupling. In order to observe a spin Hall effect a bias driven current is an essential prerequisite. The spin separation is caused via spin-orbit coupling either by Mott scattering (extrinsic spin Hall effect) or by Rashba or Dresselhaus spin splitting of the band structure (intrinsic spin Hall effect). Here we provide evidence for an elementary effect causing spin separation which is fundamentally different from that of the spin Hall effect. In contrast to the spin Hall effect it does not require an electric current to flow: It is spin separation achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show that by free carrier (Drude) absorption of terahertz radiation spin separation is achieved in a wide range of temperatures from liquid helium up to room temperature. Moreover the experimental results give evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy relaxation processes of nonequilibrium carriers.Comment: 19 pages, 4 figures, 1 tabl

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For several years, virtual environments (VEs) are promising applications to explore and manipulate 3D data and 3D worlds. Those environments are designed to be intuitive and easy to use, however, in practice no ideal solution has been proposed yet. Designers and researchers always have to make compromises due to the complexity of the human senses and technical and financial restrictions. It is widely accepted that multisensory metaphors dramatically can improve the user's performance when interaction in a VE. In this paper, we present a modelling application, for research purposes, called nVRment, which uses and combines several interaction metaphors. The aim of this application is to test in practice our newly proposed metaphors: the "Object In Hand" metaphor, which uses proprioception together with force feedback for manipulations and the "Small Scene Manipulation" which is suitable for manipulation of an object in its local context.

Despite of decades of research, creating intuitive and easy to learn interfaces for 3D virtual environments (VE) is still not obvious, requiring VE specialists to define, implement and evaluate solutions in an iterative way, often using lowlevel programming code. Moreover, quite frequently the interaction with the virtual environment may also vary dependent on the context in which it is applied, such as the available hardware setup, user experience, or the pose of the user (e.g. sitting or standing). Lacking other tools, the context-awareness of an application is usually implemented in an ad-hoc manner, using low-level programming, as well. This may result in code that is difficult and expensive to maintain. One possible approach to facilitate the process of creating these highly interactive user interfaces is by adopting a model-based user interface design. This lifts the creation of a user interface to a higher level allowing the designer to reason more in terms of high-level concepts, rather than writing programming code. In this paper, we adopt a model-based user interface design (MBUID) process for the creation of VEs, and explain how a context system using an Event-Condition-Action paradigm is added. We illustrate our approach by means of a case study.

Abstract. In the past few years, multimodal interaction is gaining importance in virtual environments. Although multimodality makes interaction with the environment more intuitive and natural for the user, the development cycle of such an environment is often a long and expensive process. In our overall field of research, we investigate how model-based design can help shorten this process by designing the application with the use of high-level diagrams. In this scope, we developed 'NiMMiT', a graphical notation especially suitable for expressing multimodal user interaction. We have already experienced the benefits of NiMMiT in several in-house applications, and are currently assessing the value of NiMMiT with respect to existing notations. In this paper we report on our comparison of NiMMiT against some well known data-driven modeling notations.

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Besides realistic haptic rendering of objects, haptic feedback can also be used to provide an abstract feedback channel. This can either be realised by a tactile or a force feedback stimulus. When using forces, care has to be taken that the user's performance is not influenced in a negative way. However, as it is not obvious to determine a suitable force, and currently not many guidelines exist. Therefore, in this paper we investigate the influence on some important parameters that define a force (shape, duration and amplitude). In order to compare different forces, we propose to use the definite integral (Force Integral, FI) which combines the considered parameters. From the conducted experiment we learn that the FI can be used (within bounds) to make an estimation of the result of the force. Besides this, we also found that above a given FI value, the user's performance degrades significantly.

Abstract. Applying force feedback applications in a therapy environment allows the patient to practice in a more independent manner, with less intervention of the therapist. Currently however, high-end devices such as the Phantom or the HapticMaster are far too expensive to provide a device per patient. Recently Novint launched a low-cost haptic device for the gaming market: the Falcon. In this paper we report on an experiment that we conducted in order to compare the Falcon and the Phantom, based on a Fitts' law targeting task. We deduced physical parameters such as inertia and damping, which were found to be different for the devices. Although from a velocity analysis these differences can be clearly seen, it turns out that the influence of different forces does not show significant differences when taking completion time and error rate into account. From a subjective experiment, we can learn that users allow the Falcon to produce slightly higher forces than the Phantom before forces are judged as too strong.