Visualizing the atomic-scale origin of metallic behavior in Kondo insulators.

A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. In this study, we visualized the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope.

Demonstration of Tunable Three-Body Interactions between Superconducting Qubits.

Nonpairwise multiqubit interactions present a useful resource for quantum information processors. Their implementation would facilitate more efficient quantum simulations of molecules and combinatorial optimization problems, and they could simplify error suppression and error correction schemes. Here, we present a superconducting circuit architecture in which a coupling module mediates two-local and three-local interactions between three flux qubits by design.

Electric polarization switching in an atomically thin binary rock salt structure.

Inducing and controlling electric dipoles is hindered in the ultrathin limit by the finite screening length of surface charges at metal-insulator junctions , although this effect can be circumvented by specially designed interfaces . Heterostructures of insulating materials hold great promise, as confirmed by perovskite oxide superlattices with compositional substitution to artificially break the structural inversion symmetry . Bringing this concept to the ultrathin limit would substantially broaden the range of materials and functionalities that could be exploited in novel nanoscale device designs.

Guided Molecular Assembly on a Locally Reactive 2D Material.

Atomically precise engineering of the position of molecular adsorbates on surfaces of 2D materials is key to their development in applications ranging from catalysis to single-molecule spintronics. Here, stable room-temperature templating of individual molecules with localized electronic states on the surface of a locally reactive 2D material, silicene grown on ZrB , is demonstrated. Using a combination of scanning tunneling microscopy and density functional theory, it is shown that the binding of iron phthalocyanine (FePc) molecules is mediated via the strong chemisorption of the central Fe atom to the sp -like dangling bond of Si atoms in the linear silicene domain boundaries.

Publisher's Note: Gating Classical Information Flow via Equilibrium Quantum Phase Transitions [Phys. Rev. Lett. 118, 147203 (2017)].

This corrects the article DOI: 10.1103/PhysRevLett.118.

Gating Classical Information Flow via Equilibrium Quantum Phase Transitions.

The development of communication channels at the ultimate size limit of atomic scale physical dimensions will make the use of quantum entities an imperative. In this regime, quantum fluctuations naturally become prominent and are generally considered to be detrimental. Here, we show that for spin-based information processing, these fluctuations can be uniquely exploited to gate the flow of classical binary information across a magnetic chain in thermal equilibrium.

Controlling electronic access to the spin excitations of a single molecule in a tunnel junction.

Spintronic phenomena underpin new device paradigms for data storage and sensing. Scaling these down to the single molecule level requires controlling the properties of current-carrying molecular orbitals to enable access to spin states through phenomena such as inelastic electron tunnelling. Here we show that the spintronic properties of a tunnel junction containing a single molecule can be controlled using the local environment as a pseudo-gate.

Sub-molecular modulation of a 4f driven Kondo resonance by surface-induced asymmetry.

Coupling between a magnetic impurity and an external bath can give rise to many-body quantum phenomena, including Kondo and Hund's impurity states in metals, and Yu-Shiba-Rusinov states in superconductors. While advances have been made in probing the magnetic properties of d-shell impurities on surfaces, the confinement of f orbitals makes them difficult to access directly. Here we show that a 4f driven Kondo resonance can be modulated spatially by asymmetric coupling between a metallic surface and a molecule containing a 4f-like moment.

Tunable magnetoresistance in an asymmetrically coupled single-molecule junction.

Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories. The scaling of such phenomena down to the single-molecule level may enable novel spintronic devices. Here, we report magnetoresistance in a single-molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts.

High-temperature antiferromagnetism in molecular semiconductor thin films and nanostructures.

The viability of dilute magnetic semiconductors in applications is linked to the strength of the magnetic couplings, and room temperature operation is still elusive in standard inorganic systems. Molecular semiconductors are emerging as an alternative due to their long spin-relaxation times and ease of processing, but, with the notable exception of vanadium-tetracyanoethylene, magnetic transition temperatures remain well below the boiling point of liquid nitrogen. Here we show that thin films and powders of the molecular semiconductor cobalt phthalocyanine exhibit strong antiferromagnetic coupling, with an exchange energy reaching 100 K.

Control of single-spin magnetic anisotropy by exchange coupling.

The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be affected strongly by this interaction. Although this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation, it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons in water molecules in a host's tissue.

Investigating individual arsenic dopant atoms in silicon using low-temperature scanning tunnelling microscopy.

We study subsurface arsenic dopants in a hydrogen-terminated Si(001) sample at 77 K, using scanning tunnelling microscopy and spectroscopy. We observe a number of different dopant-related features that fall into two classes, which we call As1 and As2. When imaged in occupied states, the As1 features appear as anisotropic protrusions superimposed on the silicon surface topography and have maximum intensities lying along particular crystallographic orientations.

Temperature- and Light-Induced Spin Crossover Observed by X-ray Spectroscopy on Isolated Fe(II) Complexes on Gold.

Using X-ray absorption techniques, we show that temperature- and light-induced spin crossover properties are conserved for a submonolayer of the [Fe(H2B(pz)2)2(2,2'-bipy)] complex evaporated onto a Au(111) surface. For a significant fraction of the molecules, we see changes in the absorption at the L2,3 edges that are consistent with those observed in bulk and thick film references. Assignment of these changes to spin crossover is further supported by multiplet calculations to simulate the X-ray absorption spectra.

Site-dependent ambipolar charge states induced by group V atoms in a silicon surface.

We report that solitary bismuth and antimony atoms, incorporated at Si(111) surfaces, induce either positive or negative charge states depending on the site of the surface reconstruction in which they are located. This is in stark contrast to the hydrogenic donors formed by group V atoms in silicon bulk crystal and therefore has strong implications for the design and fabrication of future highly scaled electronic devices. Using scanning tunnelling microscopy (STM) and density functional theory (DFT) we determine the reconstructions formed by different group V atoms in the Si(111)2 × 1 surface.

Activation energy paths for graphene nucleation and growth on Cu.

The synthesis of wafer-scale single crystal graphene remains a challenge toward the utilization of its intrinsic properties in electronics. Until now, the large-area chemical vapor deposition of graphene has yielded a polycrystalline material, where grain boundaries are detrimental to its electrical properties. Here, we study the physicochemical mechanisms underlying the nucleation and growth kinetics of graphene on copper, providing new insights necessary for the engineering synthesis of wafer-scale single crystals.

Spin texture and magnetoroton excitations at nu=1/3.

Neutral spin texture (ST) excitations at nu=1/3 are directly observed for the first time by resonant inelastic light scattering. They are determined to involve two simultaneous spin flips. At low magnetic fields, the ST energy is below that of the magnetoroton minimum.

The force needed to move an atom on a surface.

Manipulation of individual atoms and molecules by scanning probe microscopy offers the ability of controlled assembly at the single-atom scale. However, the driving forces behind atomic manipulation have not yet been measured. We used an atomic force microscope to measure the vertical and lateral forces exerted on individual adsorbed atoms or molecules by the probe tip.

Large magnetic anisotropy of a single atomic spin embedded in a surface molecular network.

Magnetic anisotropy allows magnets to maintain their direction of magnetization over time. Using a scanning tunneling microscope to observe spin excitations, we determined the orientation and strength of the anisotropies of individual iron and manganese atoms on a thin layer of copper nitride. The relative intensities of the inelastic tunneling processes are consistent with dipolar interactions, as seen for inelastic neutron scattering.

Spin coupling in engineered atomic structures.

We used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures. Linear chains of 1 to 10 manganese atoms were assembled one atom at a time on a thin insulating layer, and the spin excitation spectra of these structures were measured with inelastic electron tunneling spectroscopy. We observed excitations of the coupled atomic spins that can change both the total spin and its orientation.