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Harvesting energy from the environment offers the promise of clean power for self-sustained systems.sup.1,2. Known technologies--such as solar cells, thermoelectric devices and mechanical generators--have specific environmental requirements that restrict where they can be deployed and limit their potential for continuous energy production.sup.3-5. The ubiquity of atmospheric moisture offers an alternative. However, existing moisture-based energy-harvesting technologies can produce only intermittent, brief (shorter than 50 seconds) bursts of power in the ambient environment, owing to the lack of a sustained conversion mechanism.sup.6-12. Here we show that thin-film devices made from nanometre-scale protein wires harvested from the microbe Geobacter sulfurreducens can generate continuous electric power in the ambient environment. The devices produce a sustained voltage of around 0.5 volts across a 7-micrometre-thick film, with a current density of around 17 microamperes per square centimetre. We find the driving force behind this energy generation to be a self-maintained moisture gradient that forms within the film when the film is exposed to the humidity that is naturally present in air. Connecting several devices linearly scales up the voltage and current to power electronics. Our results demonstrate the feasibility of a continuous energy-harvesting strategy that is less restricted by location or environmental conditions than other sustainable approaches. A new type of energy-harvesting device, based on protein nanowires from the microbe Geobacter sulforreducens, can generate a sustained power output by producing a moisture gradient across the nanowire film using natural humidity., Author(s): Xiaomeng Liu [sup.1] , Hongyan Gao [sup.1] , Joy E. Ward [sup.2] , Xiaorong Liu [sup.3] , Bing Yin [sup.1] , Tianda Fu [sup.1] , Jianhan Chen [sup.3] [sup.4] [...]

The discovery of superconducting and insulating states in magic-angle twisted bilayer graphene (MATBG).sup.1,2 has ignited considerable interest in understanding the nature of electronic interactions in this chemically pristine material. The transport properties of MATBG as a function of doping are similar to those of high-transition-temperature copper oxides and other unconventional superconductors.sup.1-3, which suggests that MATBG may be a highly interacting system. However, to our knowledge, there is no direct experimental evidence of strong many-body correlations in MATBG. Here we present high-resolution spectroscopic measurements, obtained using a scanning tunnelling microscope, that provide such evidence as a function of carrier density. MATBG displays unusual spectroscopic characteristics that can be attributed to electron-electron interactions over a wide range of doping levels, including those at which superconductivity emerges in this system. We show that our measurements cannot be explained with a mean-field approach for modelling electron-electron interactions in MATBG. The breakdown of a mean-field approach when applied to other correlated superconductors, such as copper oxides, has long inspired the study of the highly correlated Hubbard model.sup.3. We show that a phenomenological extended-Hubbard-model cluster calculation, which is motivated by the nearly localized nature of the relevant electronic states of MATBG, produces spectroscopic features that are similar to those that we observed experimentally. Our findings demonstrate the critical role of many-body correlations in understanding the properties of MATBG. Scanning tunnelling spectroscopy and extended-Hubbard-model cluster calculations reveal that magic-angle twisted bilayer graphene is a strongly correlated electron system, similar to other unconventional superconductors., Author(s): Yonglong Xie [sup.1] , Biao Lian [sup.2] , Berthold Jäck [sup.1] , Xiaomeng Liu [sup.1] , Cheng-Li Chiu [sup.1] , Kenji Watanabe [sup.3] , Takashi Taniguchi [sup.3] , B. [...]