Realtime magnetic field sensing and imaging using a single spin in diamond

The Zeeman splitting of a localized single spin can be used to construct a magnetometer allowing high precision measurements of magnetic fields with almost atomic spatial resolution. While sub-{\mu}T sensitivity can in principle be obtained using pulsed techniques and long measurement times, a fast and easy-to-use method without laborious data post-processing is desirable for a scanning-probe approach with high spatial resolution. In order to measure the resonance frequency in realtime, we applied a field-frequency lock to the continuous wave ODMR signal of a single electron spin in a nanodiamond. In our experiment, we achieved a sampling rate of up to 100 readings per second with a sensitivity of 6 {\mu}T/$\sqrt{Hz}$. Using this method we have imaged the microscopic field distribution around a magnetic wire. Images with \sim 30 {\mu}T resolution and 4096 sub-micron sized pixels were acquired in 10 minutes. By measuring the field response of multiple spins on the same object we were able to partly reconstruct the orientation of the field

Compact electrically detected magnetic resonance setup

Electrically detected magnetic resonance (EDMR) is a commonly used technique for the study of spin-dependent transport processes in semiconductor materials and electro-optical devices. Here, we present the design and implementation of a compact setup to measure EDMR, which is based on a commercially available benchtop electron paramagnetic resonance (EPR) spectrometer. The electrical detection part uses mostly off-the-shelf electrical components and is thus highly customizable. We present a characterization and calibration procedure for the instrument that allowed us to quantitatively reproduce results obtained on a silicon-based reference sample with a “large-scale” state-of- the-art instrument. This shows that EDMR can be used in novel contexts relevant for semiconductor device fabrication like clean room environments and even glove boxes. As an application example, we present data on a class of environment-sensitive objects new to EDMR, semiconducting organic microcrystals, and discuss similarities and differences to data obtained for thin-film devices of the same molecule

Cotunneling through a magnetic single-molecule transistor based on N\atC60

We present an experimental and theoretical study of a magnetic single-molecule transistor based on N@C60 connected to gold electrodes. Particular attention is paid to the regime of intermediate molecule-lead coupling, where cotunneling effects manifest themselves in the Coulomb-blockade regime. The experimental results for the differential conductance as a function of bias, gate voltage, and external magnetic field are in agreement with our analysis of the tunneling rates and provide evidence of magnetic signatures in single-N@C60 devices arising from an antiferromagnetic exchange interaction between the C60 spin and the nitrogen spin.Comment: Accepted for publication in PRB Rapid Com, 4 pages, 4 figures, with supplementary information (6 pages, 3 figures

Influence of charge transfer doping on the morphologies of C-60 islands on hydrogenated diamond C(100)-(2 x 1)

Nimmrich M, Kittelmann M, Rahe P, et al. Influence of charge transfer doping on the morphologies of C-60 islands on hydrogenated diamond C(100)-(2 x 1). Physical Review B. 2012;85(3): 35420.The adsorption and island formation of C-60 fullerenes on the hydrogenated C(100)-(2 x 1):H diamond surface is studied using high-resolution noncontact atomic force microscopy in ultrahigh vacuum. At room temperature, C-60 fullerene molecules assemble into monolayer islands, exhibiting a hexagonally close-packed internal structure. Dewetting is observed when raising the substrate temperature above approximately 505 K, resulting in two-layer high islands. In contrast to the monolayer islands, these double-layer islands form extended wetting layers. This peculiar behavior is explained by an increased molecule-substrate binding energy in the case of double-layer islands, which originates from charge transfer doping. Only upon further increasing the substrate temperature to approximately 615 K, the wetting layer desorbs, corresponding to a binding energy of the charge transfer-stabilized film of 1.7 eV

Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2x1) diamond surfaces using noncontact AFM

Nimmrich M, Kittelmann M, Rahe P, et al. Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2x1) diamond surfaces using noncontact AFM. Physical Review B. 2010;81(20): 201403.High-purity, type IIa diamond is investigated by noncontact atomic force microscopy (NC-AFM). We present atomic-resolution images of both the electrically conducting hydrogen-terminated C(100)-(2 x 1) : H surface and the insulating C(100)-(2 x 1) surface. For the hydrogen-terminated surface, a nearly square unit cell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allows both hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment. Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolution images, revealing individual C-C dimers. Our results provide real-space experimental evidence for a (2 x 1) dimer reconstruction of the truly insulating C(100) surface

Tunneling Spectra of Individual Magnetic Endofullerene Molecules

The manipulation of single magnetic molecules may enable new strategies for high-density information storage and quantum-state control. However, progress in these areas depends on developing techniques for addressing individual molecules and controlling their spin. Here we report success in making electrical contact to individual magnetic N@C60 molecules and measuring spin excitations in their electron tunneling spectra. We verify that the molecules remain magnetic by observing a transition as a function of magnetic field which changes the spin quantum number and also the existence of nonequilibrium tunneling originating from low-energy excited states. From the tunneling spectra, we identify the charge and spin states of the molecule. The measured spectra can be reproduced theoretically by accounting for the exchange interaction between the nitrogen spin and electron(s) on the C60 cage.Comment: 7 pages, 4 figures. Typeset in LaTeX, updated text of previous versio

Multi-omics Reveals the Lifestyle of the Acidophilic, Mineral-Oxidizing Model Species Leptospirillum ferriphilumT.

Leptospirillum ferriphilum plays a major role in acidic, metal-rich environments, where it represents one of the most prevalent iron oxidizers. These milieus include acid rock and mine drainage as well as biomining operations. Despite its perceived importance, no complete genome sequence of the type strain of this model species is available, limiting the possibilities to investigate the strategies and adaptations that Leptospirillum ferriphilum DSM 14647T (here referred to as Leptospirillum ferriphilum T) applies to survive and compete in its niche. This study presents a complete, circular genome of Leptospirillum ferriphilum T obtained by PacBio single-molecule real-time (SMRT) long-read sequencing for use as a high-quality reference. Analysis of the functionally annotated genome, mRNA transcripts, and protein concentrations revealed a previously undiscovered nitrogenase cluster for atmospheric nitrogen fixation and elucidated metabolic systems taking part in energy conservation, carbon fixation, pH homeostasis, heavy metal tolerance, the oxidative stress response, chemotaxis and motility, quorum sensing, and biofilm formation. Additionally, mRNA transcript counts and protein concentrations were compared between cells grown in continuous culture using ferrous iron as the substrate and those grown in bioleaching cultures containing chalcopyrite (CuFeS2). Adaptations of Leptospirillum ferriphilum T to growth on chalcopyrite included the possibly enhanced production of reducing power, reduced carbon dioxide fixation, as well as elevated levels of RNA transcripts and proteins involved in heavy metal resistance, with special emphasis on copper efflux systems. Finally, the expression and translation of genes responsible for chemotaxis and motility were enhanced.IMPORTANCE Leptospirillum ferriphilum is one of the most important iron oxidizers in the context of acidic and metal-rich environments during moderately thermophilic biomining. A high-quality circular genome of Leptospirillum ferriphilum T coupled with functional omics data provides new insights into its metabolic properties, such as the novel identification of genes for atmospheric nitrogen fixation, and represents an essential step for further accurate proteomic and transcriptomic investigation of this acidophile model species in the future. Additionally, light is shed on adaptation strategies of Leptospirillum ferriphilum T for growth on the copper mineral chalcopyrite. These data can be applied to deepen our understanding and optimization of bioleaching and biooxidation, techniques that present sustainable and environmentally friendly alternatives to many traditional methods for metal extraction

Stability of C60 and N@C60 under thermal and optical exposure

N@C60, a nitrogen atom encapsulated in a fullerene shell, has an electron-nuclear spin system with outstanding coherence properties attractive for quantum computation. The stability of this molecule is known to be limited due to thermal escape of the nitrogen atom from the C60 cage but little is known about the stability towards optical excitation, which is one possible tool for an indirect scheme to manipulate and read out quantum information. Here, we report the results of a systematic study regarding thermal and optical effects on the stability of N@C60. The central result is that stability under intense laser irradiation can be obtained when the sample remains cooled below a certain temperature. Furthermore, the effect of molecules from the atmosphere or matrix (e.g. oxygen, toluene etc.) on N@C60 is discussed with respect to spin read-out experiments and the decomposition of N@C60. As a result, appropriate experimental conditions for optical quantum state read-out of this material are identified