108 research outputs found
Colloquium: Atomic spin chains on surfaces
In the present Colloquium, we focus on the properties of 1-D magnetic systems
on solid surfaces. From the emulation of 1-D quantum phases to the potential
realization of Majorana edge states, spin chains are unique systems to study.
The advent of scanning tunnelling microscope (STM) based techniques has
permitted us to engineer spin chains in an atom-by-atom fashion via atom
manipulation and to access their spin states on the ultimate atomic scale.
Here, we present the current state of research on spin correlations and
dynamics of atomic spin chains as studied by the STM. After a brief review of
the main properties of spin chains on solid surfaces, we classify spin chains
according to the coupling of their magnetic moments with the holding substrate.
This classification scheme takes into account that the nature and lifetimes of
the spin-chain excitation intrinsically depend on the holding substrate. We
first show the interest of using insulating layers on metals, which generally
results in an increase in the spin state's lifetimes such that their quantized
nature gets evident and they are individually accessible. Next, we show that
the use of semiconductor substrates promises additional control through the
tunable electron density via doping. When the coupling to the substrate is
increased for spin chains on metals, the substrate conduction electron mediated
interactions can lead to emergent exotic phases of the coupled spin
chain-substrate conduction electron system. A particularly interesting example
is furnished by superconductors. Magnetic impurities induce states in the
superconducting gap. Due to the extended nature of the spin chain, the in-gap
states develop into bands that can lead to the emergence of 1-D topological
superconductivity and, consequently to the appearance of Majorana edge states
Non-collinear spin states in bottom-up fabricated atomic chains
Non-collinear spin states with unique rotational sense, such as chiral
spin-spirals, are recently heavily investigated because of advantages for
future applications in spintronics and information technology and as potential
hosts for Majorana Fermions when coupled to a superconductor. Tuning the
properties of such spin states, e.g., the rotational period and sense, is a
highly desirable yet difficult task. Here, we experimentally demonstrate the
bottom-up assembly of a spin-spiral derived from a chain of Fe atoms on a Pt
substrate using the magnetic tip of a scanning tunneling microscope as a tool.
We show that the spin-spiral is induced by the interplay of the Heisenberg and
Dzyaloshinskii-Moriya components of the Ruderman-Kittel-Kasuya-Yosida
interaction between the Fe atoms. The relative strengths and signs of these two
components can be adjusted by the interatomic Fe distance, which enables
tailoring of the rotational period and sense of the spin-spiral.Comment: 16 pages, 5 figure
Itinerant Nature of Atom-Magnetization Excitation by Tunneling Electrons
We have performed single-atom magnetization curve (SAMC) measurements and
inelastic scanning tunneling spectroscopy (ISTS) on individual Fe atoms on a
Cu(111) surface. The SAMCs show a broad distribution of magnetic moments with
\unit[3.5]{\mu_{\rm B}} being the mean value. ISTS reveals a magnetization
excitation with a lifetime of \unit[200]{fsec} which decreases by a factor of
two upon application of a magnetic field of \unit[12]{T}. The experimental
observations are quantitatively explained by the decay of the magnetization
excitation into Stoner modes of the itinerant electron system as shown by newly
developed theoretical modeling.Comment: 3 Figures, Supplement not included, updated version after revisio
Long spin relaxation times in a transition metal atom in direct contact to a metal substrate
Long spin relaxation times are a prerequisite for the use of spins in data
storage or nanospintronics technologies. An atomic-scale solid-state
realization of such a system is the spin of a transition metal atom adsorbed on
a suitable substrate. For the case of a metallic substrate, which enables
directly addressing the spin by conduction electrons, the experimentally
measured lifetimes reported to date are on the order of only hundreds of
femtoseconds. Here, we show that the spin states of iron atoms adsorbed
directly on a conductive platinum substrate have an astonishingly long spin
relaxation time in the nanosecond regime, which is comparable to that of a
transition metal atom decoupled from the substrate electrons by a thin
decoupling layer. The combination of long spin relaxation times and strong
coupling to conduction electrons implies the possibility to use flexible
coupling schemes in order to process the spin-information
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