Measurement of the conductance of a hydrogen molecule

Recent years have shown steady progress towards molecular electronics(1,2), in which molecules form basic components such as switches(3-5), diodes(6) and electronic mixers(7). Often, a scanning tunnelling microscope is used to address an individual molecule, although this arrangement does not provide long-term stability. Therefore, metal-molecule-metal links using break-junction devices(8-10) have also been explored; however, it is difficult to establish unambiguously that a single molecule forms the contact(11). Here we show that a single hydrogen molecule can form a stable bridge between platinum electrodes. In contrast to results for organic molecules, the bridge has a nearly perfect conductance of one quantum unit, carried by a single channel. The hydrogen bridge represents a simple test system in which to understand fundamental transport properties of single-molecule devices.