Nanoscale confinement of adsorbed CO molecules in an anthraquinone network on Cu(111) with a pore size of ≈4  nm arranges the CO molecules in a shell structure that coincides with the distribution of substrate confined electronic states. Molecules occupy the states approximately in the sequence of rising electron energy. Despite the sixfold symmetry of the pore boundary itself, the adsorbate distribution adopts the threefold symmetry of the network-substrate system, highlighting the importance of the substrate even for such quasi-free-electron systems.

Time-integrated quantities such as work and heat increase incessantly in time during nonequilibrium processes near steady states. In the long-time limit, the average values of work and heat become asymptotically equivalent to each other, since they only differ by a finite energy change in average. However, the fluctuation theorem (FT) for the heat is found not to hold with the equilibrium initial ensemble, while the FT for the work holds. This reveals an intriguing effect of everlasting initial memory stored in rare events. We revisit the problem of a Brownian particle in a harmonic potential dragged with a constant velocity, which is in contact with a thermal reservoir. The heat and work fluctuations are investigated with initial Boltzmann ensembles at temperatures generally different from the reservoir temperature. We find that, in the infinite-time limit, the FT for the work is fully recovered for arbitrary initial temperatures, while the heat fluctuations significantly deviate from the FT characteristics except for the infinite initial-temperature limit (a uniform initial ensemble). Furthermore, we succeed in calculating finite-time corrections to the heat and work distributions analytically, using the modified saddle point integral method recently developed by us. Interestingly, we find noncommutativity between the infinite-time limit and the infinite-initial-temperature limit for the probability distribution function (PDF) of the heat.

We numerically study the superconductor-insulator phase transition in a model disordered two-dimensional ͑2D͒ superconductor as a function of applied magnetic field. The calculation involves quantum Monte Carlo calculations of the ͑2+1͒D XY model in the presence of both disorder and magnetic field. The XY coupling is assumed to have the form −J cos͑ i − j − A ij ͒, where A ij has a mean of zero and a standard deviation ⌬A ij . In a real system, such a model would be approximately realized by a 2D array of small Josephson-coupled grains with slight spatial disorder and a uniform applied magnetic field. The different values ⌬A ij then correspond to an applied field such that the average number of flux quanta per plaquette has various integer values N: larger N corresponds to larger ⌬A ij . For any value of ⌬A ij , there appears to be a critical coupling constant K c ͑⌬A ij ͒ = ͱ ͓J / ͑2U͔͒ c , where U is the charging energy, below which the system is a Mott insulator; there is also a corresponding critical conductivity ‫ء‬ ͑⌬A ij ͒ at the transition. For ⌬A ij = ϱ, the order parameter of the transition is a renormalized coupling constant g. Using a numerical technique appropriate for disordered systems, we show that the transition at this value of ⌬A ij takes place from an insulating ͑I͒ phase to a Bose glass ͑BG͒ phase, and that the dynamical critical exponent characterizing this transition is z ϳ 1.3. By contrast, z = 1 for this model at ⌬A ij = 0. We suggest that the superconductor-to-insulator transition is actually of this I to BG class at all nonzero ⌬A ij 's, and we support this interpretation by both numerical evidence and an analytical argument based on the Harris criterion ͓A. B. Harris, J. Phys. C 7, 1671 ͑1974͔͒. K c is found to be a monotonically increasing function of ⌬A ij . For certain values of K, a disordered Josephson array may undergo a transition from an ordered, Bose glass phase to an insulator with increasing ⌬A ij .

Adsorbing anthracene on a Cu͑111͒ surface results in a wide range of complex and intriguing superstructures spanning a coverage range from 1 per 17 to 1 per 15 substrate atoms. In accompanying first-principles density-functional theory calculations we show the essential role of van der Waals interactions in estimating the variation in anthracene adsorption energy and height across the sample. We can thereby evaluate the compression of the anthracene film in terms of continuum elastic properties, which results in an effective Young's modulus of 1.5 GPa and a Poisson ratio Ϸ0.1. These values suggest interpretation of the molecular monolayer as a porous material-in marked congruence with our microscopic observations.