Spin mapping at the nanoscale and atomic scale

Wiesendanger, R.

doi:10.1103/revmodphys.81.1495

Cited by 673 publications

(639 citation statements)

References 216 publications

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“…When the material has significant spin splitting, e.g., due to intrinsic spin-orbit coupling or by external exchange field from a ferromagnetic layer [11], the Fermi surface matching may occur for only one spin orientation, then the hidden quantum mirage becomes spin-selective. This can be detected by spin-polarized STM [35,36].…”

mentioning

confidence: 99%

Hidden quantum mirage by negative refraction in semiconductor P-N junctions

Zhang¹,

Zhu²,

Yang³

et al. 2016

Phys. Rev. B

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We predict a novel quantum interference based on the negative refraction across a semiconductor P-N junction: with a local pump on one side of the junction, the response of a local probe on the other side behaves as if the disturbance emanates not from the pump but instead from its mirror image about the junction. This phenomenon is guaranteed by translational invariance of the system and matching of Fermi surfaces of the constituent materials, thus it is robust against other details of the junction (e.g., junction width, potential profile, and even disorder). The recently fabricated P-N junctions in 2D semiconductors provide ideal platforms to explore this phenomenon and its applications to dramatically enhance charge and spin transport as well as carrier-mediated long-range correlation.PACS numbers: 73.40. Lq, 75.30.Hx, 72.80.Vp Half a century ago, Veselago proposed the concept of negative refraction for electromagnetic waves [1][2][3][4]: upon transition from a medium with positive refractive index across a sharp interface into a negative index medium, a diverging pencil of rays is coherently refocused to form a sharp image or "quantum mirage" [5], similar to the bending of light to create mirages in the atmosphere. In the past decade, negative refraction and mirage have been observed for electromagnetic waves of various frequencies (see Ref.[6] for a review) and for cold atoms [7,8]. In 2007, Cheianov et al. [9] proposed the interesting idea that a sharp P-N junction of graphene can exhibit negative refraction and hence focus electrons out of a local pump into a sharp quantum mirage. This effect has been widely used in theoretical proposals to control charge and/or spin transport for massless Dirac fermions in semiconductors (see for a few examples). However, a sharp quantum mirage requires the junction to be sharp compared with the electron wavelength (∼ a few nanometers), otherwise it would disappear due to the path-dependent phase accumulation inside the junction. This makes the observation and application of this effect an experimentally challenging task [13].In this letter, we theoretically demonstrate that in many situations where the quantum mirage is no longer visible, its effect still exists, which could make the response across the P-N junction independent of distance. As a basic observation in physics, the response amplitude in a d-dimensional uniform system decays at least as fast as 1/R (d−1)/2 with distance R, irrespective of the energy dispersion, spin-orbit coupling, etc. This directly leads to rapid decay of many physical properties, such as the charge and spin conductivity [14] As an example, we demonstrate that the P-N junction could dramatically enhance the carriermediated long-range interaction between localized magnetic moments by several orders of magnitudes.For an intuitive physical picture about the hidden quantum mirage, we start from a sharp P-N junction as shown in Fig. 1(a). Here the plane waves excited by a local pump (filled red circle) in the N region is perfectly focuse...

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confidence: 99%

Hidden quantum mirage by negative refraction in semiconductor P-N junctions

Zhang¹,

Zhu²,

Yang³

et al. 2016

Phys. Rev. B

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“…Although there has been considerable progress in growth and study of Fe-SCs using combined MBE-STM systems, many unconventional superconductors, such as YBa 2 Cu 3 O 7Àx , La 2Àx Sr x CuO 4 , or Ba 1Àx K x BiO 3 , 127,154 cannot be cleaved to expose atomically flat surfaces with electronic states clearly representative of the bulk. Second, spin-polarized STM has been very successful in spin-resolved imaging of systems of magnetic elements 155 yet SP-STM has not yet been successfully applied to unconventional superconductors. STM will surely continue to make significant contributions towards understanding the role of chemical disorder in shaping the electronic properties of superconductors.…”

Section: Chemical Disorder and Vortex Pinningmentioning

confidence: 99%

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Zeljkovic

Hoffman

2013

Phys. Chem. Chem. Phys.

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Many of today's forefront materials, such as high-T c superconductors, doped semiconductors, and colossal magnetoresistance materials, are structurally, chemically and/or electronically inhomogeneous at the nanoscale. Although inhomogeneity can degrade the utility of some materials, defects can also be advantageous. Quite generally, defects can serve as nanoscale probes and facilitate quasiparticle scattering used to extract otherwise inaccessible electronic properties. In superconductors, nonstoichiometric dopants are typically necessary to achieve a high transition temperature, while both structural and chemical defects are used to pin vortices and increase critical current. Scanning tunneling microscopy (STM) has proven to be an ideal technique for studying these processes at the atomic scale.In this perspective, we present an overview of STM studies on chemical disorder in unconventional superconductors, and discuss how dopants, impurities and adatoms may be used to probe, pin or enhance the intrinsic electronic properties of these materials.

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“…In addition, STM spectroscopy unveils quantum spin configurations in artificially coupled spin chains at the atomic scale. [69][70][71] Thus, it is very promising for detecting a nanoscale electric polarization correlated with local spin states, and the confirmation of the KIEP will stimulate a new application of the Kondo effect to spintronic and multiferroic devices. From a different viewpoint of the experiments, the ASO-coupling-dependent KIEP is expected to give a relevant contribution to the linear conductance between two leads through a single QD of the TTQD, which can be mapped to the present Anderson model for the TTQD with a single lead.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Antisymmetric Spin–Orbit Coupling Effect on Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot

2017

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We study the local antisymmetric spin-orbit (ASO) coupling effect on spin, orbital, and charge degrees of freedom for the Kondo effect in a triangular triple quantum dot (TTQD). Here, one of the three QDs is coupled to a metallic lead through electron tunneling, and a local electric polarization is induced by the Kondo effect. The ASO interaction is introduced in the other two coupled QDs on the opposite side of the lead. Generally, the ASO coupling effect is very weak and not easily detectable, but it essentially causes spin and charge reconfigurations in the TTQD through the Kondo effect. Using an extended Anderson model for the TTQD Kondo system, we elucidate that the ASO coupling gives rise to a considerable reduction of the emergent electric polarization, as a consequence of the parity mixing of molecular orbitals in the triangular loop as well as the spin-up and spin-down coupling of local electrons. The latter leads to a local diamagnetic susceptibility owing to the ASO coupled spins. We also show that the Kondo-induced electric polarization can be controlled by the ASO coupling as well as by the magnetic flux penetrating through the TTQD.

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Spin mapping at the nanoscale and atomic scale

Cited by 673 publications

References 216 publications

Hidden quantum mirage by negative refraction in semiconductor P-N junctions

Hidden quantum mirage by negative refraction in semiconductor P-N junctions

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Antisymmetric Spin–Orbit Coupling Effect on Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot

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