Scanning tunneling spectroscopy under pulsed spin injection

Ngai, J. H.; Tseng, Yu‐Chih; Morales, P.; Pribiag, Vlad; Wei, J.Y.T.; Chen, F.; Perovic, D. D.

doi:10.1063/1.1667281

Cited by 10 publications

(8 citation statements)

References 15 publications

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“…Spin injection depletes the superconducting condensate and can result in switching to a normal state of much higher resistance (Dong et al, 1997;Vas'ko et al, 1997;Takahashi et al, 1999;Wei et al, 1999;Yeh et al, 1999). A critical review of possible spurious effects in reported experiments (Gim et al, 2001) has also stimulated the development of a novel detection technique which uses scanning tunneling spectroscopy combined with pulsed quasiparticle spin injection to minimize Joule heating (Ngai et al, 2004;see Sec. IV.A.1).…”

Section: F/n Junctionmentioning

confidence: 99%

“…IV.A.3), which, in addition to the usual quasiparticle tunneling, contributes to the I-V characteristics of a F/I/S junction (Hu and Yan, 1999;Kashiwaya et al, 1999;Zhu et al, 1999;Valls, 1999, 2000; a simpler N/I/S case is reviewed by Hu, 1998 andTanaka, 2000). The suppression of a zero-bias conductance peak, measured by a scanning tunneling microscope, was recently used to detect spin injection into a high-temperature superconductor (Ngai et al, 2004).…”

Section: F/i/s Tunnelingmentioning

confidence: 99%

“…1, this alone is usually not sufficient for spintronic applications, which typically require current flow and/or manipulation of the nonequilibrium spin (polarization). 17 The importance of generating nonequilibrium spin is not limited to device applications; it can also be used as a sensitive spectroscopic tool to study a wide variety of fundamental properties ranging from spin-orbit and hyperfine interactions (Meier and Zakharchenya, 1984) to the pairing symmetry of high-temperature superconductors (Vas'ko et al, 1997;Wei et al, 1999;Tsuei and Kirtley, 2000;Ngai et al, 2004) and the creation of spin-polarized beams to measure parity violation in high-energy physics (Pierce and Celotta, 1984).…”

Section: Spin Injection and Optical Orientationmentioning

confidence: 99%

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Spintronics: Fundamentals and applications

2004

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Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics. CONTENTS

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Section: F/n Junctionmentioning

confidence: 99%

Section: F/i/s Tunnelingmentioning

confidence: 99%

Section: Spin Injection and Optical Orientationmentioning

confidence: 99%

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Spintronics: Fundamentals and applications

2004

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“…The interest to study spin accumulation, one of the key elements in spintronic applications [1], is not limited to novel spin-based devices. Spin injection can also be used as a sensitive spectroscopic tool to study fundamental properties such as the pairing symmetry of unconventional superconductors [2,3], Skyrmion excitations in the quantum Hall regime [4,5], and spincharge separation in non-Fermi liquids [6,7]. While spin accumulation in metals was first demonstrated by Johnson and Silsbee [8], the basis for understanding spin injection and, more generally, spin-polarized transport, dates back to Mott [9].…”

mentioning

confidence: 99%

Temperature-Dependent Asymmetry of the Nonlocal Spin-Injection Resistance: Evidence for Spin Nonconserving Interface Scattering

2005

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We report nonlocal spin injection and detection experiments on mesoscopic Co-Al2O3-Cu spin valves. We have observed a temperature dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature.

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“…7 was done on YBa 2 Cu 3 O 7−␦ under a spin-injected current. 9 It would be interesting to see a similar experiment performed on an HTS sample carrying a supercurrent in the near future. As a natural extension of our previous work, 7 here we examine the LDOS induced by a strong defect which replaces a Cu 2+ ion in the top CuO layer of a current carrying HTS.…”

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confidence: 99%

Impurity-induced local density of states in ad-wave superconductor carrying a supercurrent

Zhang

Ting

2005

Phys. Rev. B

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The local density of states ͑LDOS͒ and its Fourier component induced by a unitary impurity in a supercurrent-carrying d-wave superconductor are investigated. Both of these quantities possess a reflection symmetry about the line passing through the impurity site and along the supercurrent if it is applied along the antinodal or nodal direction. With increasing supercurrent, both the coherence and resonant peaks in LDOS are suppressed and slightly broadened. Under a supercurrent along the antinodal direction, the coherence peaks split into double peaks. The modulation wave vectors associated with the elastic scatterings of quasiparticles by the defect from one constant-energy piece of the Fermi surface to another are displayed as bright or dark spots in the Fourier space of the LDOS image, and they may be suppressed or enhanced and shifted, depending on the applied current and the bias voltage. The understanding of the local physics in cuprate or hightemperature superconductors ͑HTS͒ is one of the most challenging problems in condensed matter physics today. Different from the conventional s-wave superconductors, the HTS have very complex phase diagrams depending on doping and chemical composition. It is also well established that the superconducting order parameter in the cuprates has predominantly d-wave symmetry.1 The zero-bias conductance peak ͑ZBCP͒ in the tunneling spectroscopy of normal metalcuprate superconductor junction with non-͑n0m͒-directional contact provides one of the direct evidences for this symmetry.2 Due to the d-wave nature of the order parameter, impurities inserted into cuprates can serve as an important tool to explore the physics of HTS. Theoretical calculations of the local density of states ͑LDOS͒ predicted that a strong potential scatterer could induce a resonance peak near the Fermi level at sites near the impurity. 3,4 This resonant peak near zero-bias voltage was observed at and near the sites of Zn impurities in Bi 2 Sr 2 CaCu 2 O 8+␦ by scanning tunneling microscopy ͑STM͒.5 In addition, an interference pattern with fourfold symmetry was also detected in the STM image. 5When a superconductor carries a supercurrent ͑J s ͒, Cooper pairs with finite momentum appear in the system. This would drastically affect the electronic structure of the superconductor, including the elementary excitation spectrum, the order parameter symmetry, and the tunneling spectroscopy.6-8 With increasing supercurrent velocity, the superconducting order parameter can be depressed. Meanwhile, the supercurrent density first increases monotonously and then arrives at a maximum value, which is called the critical current density. Beyond that, superconductivity becomes unstable and collapses to the normal state. So the supercurrent in the stable regime can be also used as a probe to further understand the quasiparticle excitations in HTS. Moreover, a better understanding of the property of a superconductor under an applied J s may have the potential for device applications.In Ref. 7, we have studied the tunneling co...

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Scanning tunneling spectroscopy under pulsed spin injection

Cited by 10 publications

References 15 publications

Spintronics: Fundamentals and applications

Spintronics: Fundamentals and applications

Temperature-Dependent Asymmetry of the Nonlocal Spin-Injection Resistance: Evidence for Spin Nonconserving Interface Scattering

Impurity-induced local density of states in ad-wave superconductor carrying a supercurrent

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