Conventional theory predicts that ultrahigh lattice thermal conductivity can only occur in crystals composed of strongly bonded light elements, and that it is limited by anharmonic three-phonon processes. We report experimental evidence that departs from these long-held criteria. We measured a local room-temperature thermal conductivity exceeding 1000 watts per meter-kelvin and an average bulk value reaching 900 watts per meter-kelvin in bulk boron arsenide (BAs) crystals, where boron and arsenic are light and heavy elements, respectively. The high values are consistent with a proposal for phonon-band engineering and can only be explained by higher-order phonon processes. These findings yield insight into the physics of heat conduction in solids and show BAs to be the only known semiconductor with ultrahigh thermal conductivity.

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Previous research has mainly focused on the determinants of consumers’ complaint channel choices. Little attention has been paid to the behavioral consequences of different complaint channels, particularly different complaint devices. Drawing on spatial crowding perception theory, this study finds that in an online complaint context, consumers’ complaint intensity is shaped by complaint devices that differ in screen size. Crowding perception produced by visually restrictive tension mediates the relationship between the screen size of the complaint device and the complaint intensity. The results of secondary data confirm that consumers’ complaint intensity is higher while complaining through a small-screen device (as opposed to a large-screen one). Three scenario-based experiments are conducted to examine the role of perceived spatial crowding in producing a more intense complaint behavior when complaints are submitted through smaller screen devices (as opposed to larger screen devices). The fourth experiment reveals that crowding perception can be lessened by adjusting certain design elements of the interface, ultimately mitigating the intensity of the complaint submitted through a small-screen device. Our research identifies the specific causality and underlying mechanism of the influence of device type on consumers’ postconsumption behavior, thus contributing to clarify some ambiguities in the literature.