Measuring Overlaps in Mesoscopic Spin Glasses via Conductance Fluctuations

Carpentier, David; Orignac, Edmond

doi:10.1103/physrevlett.100.057207

Cited by 14 publications

(14 citation statements)

References 25 publications

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“…Some (indirect) arguments in favour of multiple pure states are discussed below (Section 5c). Also, following a theoretical suggestion stating that the correlation of the conductance fluctuations in two spin states should be a direct function of their overlap [39], a new experimental approach using transport measurements on mesoscopic samples has been developed. Magneto-resistance traces are observed, which are reproducible until the sample is heated well over T g .…”

Section: C Spin Glass Transition : Open Questionsmentioning

confidence: 99%

Spin Glasses: Experimental Signatures and Salient Outcomes

Vincent

Dupuis

2018

Springer Series in Materials Science

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Within the wide class of disordered materials, spin glasses occupy a special place because of their conceptually simple definition of randomly interacting spins. Their modelling has triggered spectacular developments of out-of-equilibrium statistical physics, as well analytically as numerically, opening the way to a new vision of glasses in general. "Real" spin glasses are disordered magnetic materials which can be very diverse from the chemist's point of view, but all share a number of common properties, laying down the definition of generic spin glass behaviour. This paper aims at giving to non-specialist readers an idea of what spin glasses are from an experimentalist's point of view, describing as simply as possible their main features as they can be observed in the laboratory, referring to numerous detailed publications for more substantial discussions and for all theoretical developments, which are hardly sketched here. We strived to provide the readers who are interested in other glassy materials with some clues about the potential of spin glasses for improving their understanding of disordered matter. At least, arousing their curiosity for this fascinating subject will be considered a success.

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Section: C Spin Glass Transition : Open Questionsmentioning

confidence: 99%

Spin Glasses: Experimental Signatures and Salient Outcomes

Vincent

Dupuis

2018

Springer Series in Materials Science

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“…by rotating or flipping the spins of impurities. Comparing the conductance obtained in both spin configurations mimics the experimental measurement of the conductance of a low-temperature canonical spin glass after two successive quenches [11,42], without the necessary restrictions of analytical approaches [11]. Experimentally, this approach could give access to the fundamental properties of a spin glass, which have never been measured.…”

Section: Resultsmentioning

confidence: 90%

Crossover between universality classes in a magnetically disordered metallic wire

Paulin

Carpentier²

2012

New J. Phys.

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In this paper, we present the numerical results of conduction in a disordered quasi-one-dimensional wire in the possible presence of magnetic impurities. Our analysis leads us to the study of universal properties in different conduction regimes, such as the localized and metallic ones. In particular, we analyze the crossover between universality classes occurring when the strength of magnetic disorder is increased. For this purpose, we use a numerical Landauer approach, and derive the scattering matrix of the wire from the electron's Green's function. t i j is the hopping term from site i to j. In the following, t i j will take two different values: t i j = t // in the longitudinal x-direction and t i j = t ⊥ in the transverse y-direction. The scalar disorder potential V = {v i } i is diagonal in electron-spin space. We choose the v i to be random scalars uniformly distributed in the interval [−W/2, W/2]. In this work, we have chosen without loss of generality to fix t // = 1 so that all energy scales are relative to the bandwidth t // = 1, and the amplitude of disorder W = 0.6. In equation (1), s, s label the SU(2) spin of electrons and the S i account for spins of the frozen magnetic impurities. A realistic choice for these frozen New Journal of Physics 14 (2012) 023026 (http://www.njp.org/) 〈 g 2 〉 c J = 0.025 J = 0.05 J = 0.075 J = 0.1 J = 0.15 J = 0.2 J = 0.3 J = 0.4 Analytical fits Quasi 1d UCF L y = 40

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“…It has been widely recognized that transport measurement can be a powerful tool to probe the quantum coherence in metallic systems [4], and that this concept can be extended to spin glasses [5]. Recently, the interest in quantum transport measurements in spin glasses has been even renewed thank to the idea that this type of measurements could give access to the structure of the ground state of the system [6].…”

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confidence: 99%

Magnetic Dephasing in Mesoscopic Spin Glasses

et al. 2013

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We have measured Universal Conductance Fluctuations in the metallic spin glass Ag : M n as a function of temperature and magnetic field. From this measurement, we can access the phase coherence time of the electrons in the spin glass. We show that this phase coherence time increases with both the inverse of the temperature and the magnetic field. From this we deduce that decoherence mechanisms are still active even deep in the spin glass phase.PACS numbers: 75.50.Lk, 75.20.Hr, Spin glasses are one of the most fascinating states of matter. It has attracted the interest of a large community for several decades, as it is one of the most fundamental problem in Condensed Matter Physics [2]. Spin Glass appears when magnetic atoms are randomly diluted in a non-magnetic metallic host. As the spatial distribution is random, so are the rkky interactions between the spins. This leads to a frustration between the magnetic moments and their couplings. It is this interplay between disorder and frustration that leads to the formation of a spin glass below a transition temperature T sg . The very nature of the ground state is still heavily debated and may consist in an unconventional state of matter with remarkable behavior [3]. Transport properties of these metallic spin glasses, however, have not been studied thoroughly. In particular, only very few studies, experimental or theoretical, have addressed the question of the quantum coherence of the electrons in a metallic spin glass, and it is usually taken for granted that, as spins are frozen, inelastic scattering processes due to spins are also frozen and one should recover the coherence time observed in a Fermi liquid.It has been widely recognized that transport measurement can be a powerful tool to probe the quantum coherence in metallic systems [4], and that this concept can be extended to spin glasses [5]. Recently, the interest in quantum transport measurements in spin glasses has been even renewed thank to the idea that this type of measurements could give access to the structure of the ground state of the system [6].In this Letter, we present measurements of Universal Conductance Fluctuations (ucfs) in a metallic spin glass as a function of temperature and magnetic field. From this we deduce the phase coherence time of the electrons; we show it increases as the temperature decreases, in agreement with theoretical predictions. Moreover, from the magnetic field dependence of the decoherence rate, we show that decoherence mechanisms persist deep in the spin glass phase.Samples have been fabricated on a silicon/silicon oxide wafer using standard electron-beam lithography on polymethyl-methacrylate (pmma) resist. Geometry of the sample consists in a long (length L ≈ 2 µm) and thin (width w ≈ 50 nm, thickness t ≈ 40 nm) wire (see inset of figure 1). Several contacts have been put along the wire, in order to measure the resistance over different lengths and to thermalize properly the electrons along the wire. Silver has been evaporated using a dedicated electron gun evaporat...

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Measuring Overlaps in Mesoscopic Spin Glasses via Conductance Fluctuations

Cited by 14 publications

References 25 publications

Spin Glasses: Experimental Signatures and Salient Outcomes

Spin Glasses: Experimental Signatures and Salient Outcomes

Crossover between universality classes in a magnetically disordered metallic wire

Magnetic Dephasing in Mesoscopic Spin Glasses

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