Geometry dependence of the conductance fluctuations in metallic nanostructures

Scheer, Elke; Löhneysen, H. v.; Hein, Herbert

doi:10.1016/0921-4526(95)00565-x

Cited by 4 publications

(8 citation statements)

References 17 publications

(23 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The experimental details and results of the measurements in the normal geometry u 90 ± have been discussed in detail previously [12,13]. The rms amplitudes of the fluctuations have been found to be in very good agreement with the theoretical predictions for the quasi-1D case.…”

supporting

confidence: 67%

See 1 more Smart Citation

Angular Dependence of Universal Conductance Fluctuations in Noble-Metal Nanowires

et al. 1997

Self Cite

View full text Add to dashboard Cite

We investigate fluctuations in the magnetoconductance (measured at T ഠ 50 mK) of noble-metal nanowires in a mesoscopic two-lead configuration, with lengths 500 and 1000 nm and widths w between 45 and 360 nm. We determine the dependence of the correlation field B c on the angle u between the direction of the magnetic field and the long axis of the wires. u is changed at low T continuously from 90 ± (usual geometry) to 0 ± . We present a calculation taking into account the 3D diffusive motion of the conduction electrons describing the angular dependence of B c . We compare this B c ͑u͒ dependence with conductance fluctuations observed while sweeping u at constant magnetic field. Universal conductance fluctuations (UCF) in metals are a direct manifestation of quantum interference of electron wave packets. They can be observed if the sample dimensions are smaller than or comparable to the phase coherence length l f ͑Dt f ͒ 1͞2 (D y F l͞3 is the diffusion constant and t f is the phase-breaking scattering time) for conduction electrons [1,2]. In polycrystalline metal films l f is of the order of 1 mm at very low temperatures T , 1 K, whereas the elastic mean free path l is about 10 to 50 nm. In this diffusive regime the electrical conductance G is influenced by the interference of electronic trajectories which is sensitive to small changes in the Hamiltonian. G is found to fluctuate around a mean value G as a function of an external control parameter as, for example, the Fermi energy [3], the transport voltage [4,5], the perpendicular magnetic field [1], configuration of the scattering centers [6] or, as we will show here, the angle between external magnetic field and current direction. In a mesoscopic two-lead configuration, i.e., when within the phase coherent sample volume l 3 f only two measuring probes are in contact with the mesoscopic sample, the rms amplitude of the fluctuations depends only very weakly on the sample shape (length L, width w, and thickness d) as long as the transport is diffusive and coherentThe properties of the fluctuations in all these realizations are essentially the same with the only exception being that the rms amplitude observed for fluctuations measured as a function of the magnetic field B is smaller by a factor p 2 because of time-reversal symmetry breaking [7]. An additional reduction of the rms amplitude by a factor of 2 occurs in metals with strong spin-orbit scattering. Altogether, one expects a saturation rms amplitude of magnetoconductance fluctuations for Au or Ag of rms G 1D 0.26e 2 ͞h for quasi-1D wires [9].The characteristic fluctuation period B c , the correlation field, is a measure of the area A f enclosed by typical interference paths since A f B c Cf 0 , where f 0 h͞e is the elementary flux quantum, in analogy to the wellknown Aharonov-Bohm effect in ring structures [1]. Here C is a constant of order unity [7]. B c is given by the half width at half maximum ( HWHM) of the autocorrelation function F͑DB͒ of the magnetoconductance curves. Because all coherent trajectorie...

show abstract

supporting

confidence: 67%

“…The contribution of the wide contact pads to the UCF is negligible for L 1000 nm and leads to B c * 400 mT with very small amplitude for L 500 nm. This can clearly be distinguished from the pattern of the wires themselves (B c & 100 mT) [13]. [12] for details) of the data yields the rms amplitudes (for u 90 ± ) given in Table I for samples 1 to 5.…”

mentioning

confidence: 99%

Angular Dependence of Universal Conductance Fluctuations in Noble-Metal Nanowires

et al. 1997

Self Cite

View full text Add to dashboard Cite

show abstract

“…The large error in¸P is caused by the small number of samples (2}4) for each c as well as an uncertainty in the data analysis due to the restricted "eld range. Furthermore, the simple relation B &¸\ P may be violated by up to 20% in the case of spin}orbit scattering [6].Two regimes in Mn concentration can be distinguished: c:84 ppm and c9315 ppm.¸P+750 nm for the nominally pure Cu sample is in good agreement with previous results for Au and Ag [5]. A small amount of magnetic impurities reduces¸P by a factor of two:…”

supporting

confidence: 79%

“…Two regimes in Mn concentration can be distinguished: c:84 ppm and c9315 ppm.¸P+750 nm for the nominally pure Cu sample is in good agreement with previous results for Au and Ag [5]. A small amount of magnetic impurities reduces¸P by a factor of two: P +350 nm for c"31 ppm and 84 ppm.…”

supporting

confidence: 77%

See 1 more Smart Citation

Universal conductance fluctuations in Cu : Mn nanocontacts

Löhneysen

Paschke

Weber

et al. 2000

Physica B: Condensed Matter

View full text Add to dashboard Cite

Universal conductance #uctuations in Cu : Mn nano-contacts of di!erent Mn concentrations c yield the phase coherence length¸P which exhibits a minimum at c+100 ppm. Above this concentration which marks the onset of a spin-glass state below 0.2 K,¸P depends on the magnetic "eld range, rising to nearly the c"0 value for B3 [9.5, 12.5 T] and leveling-o! at a much lower value for B3 [0, 3 T]. These results demonstrate the recovery of phase coherence due to spin-glass correlations and a strong magnetic "eld.2000 Elsevier Science B.V. All rights reserved.Keywords: Mesoscopics; Phase coherent transport; Spin-glasses; Spin scattering Universal conductance #uctuations (UCF) arising from quantum interferences between di!erent electron paths [1] can be used to probe the complex frozen magnetic order in metallic spin-glasses [2,3]. Here we report on UCF in Cu : Mn nanocontacts with a Mn concentration c between 31 and 920 ppm, encompassing the transition from the single-impurity regime to the spin-glass state. We estimate the spin-glass temperature for our thin samples ¹ "0.06, 0.43 and 1.08 K for 31, 315 and 920 ppm Mn, respectively [4].The samples were fabricated by electron-beam lithography followed by #ash-evaporation and lift-o! in a two-lead geometry. The contact width w varies between 60 and 480 nm, and the length¸between 100 and 2000 nm. The Cu : Mn "lms (thickness 10}20 nm) were mounted within the mixing chamber of a He}He dilution refrigerator with a base temperature of ¹+0.05 K.A typical R(B) curve is shown in Fig. 1a. The sample with c"920 ppm exhibits a resistance (R) maximum at B"0. The negative magnetoresistance (MR) arises from the suppression of spin}#ip scattering by the magnetic "eld B. The resistance #uctuations R obtained from the R(B) data by subtracting the negative MR using a spline "t, yield the conductance #uctuations G"! R/R , where R is the resistance of the nanobridge, i.e. the contribution of the contact leads subtracted from R (R "17.7 for the sample of Fig. 1). Fig. 1b shows G whose amplitude increases with the magnetic "eld. G(B) #uctuates on a magnetic-"eld scale B which is determined by the magnetic #ux "B A A P through a phase-coherent region A P where "h/e. A P is bounded by the width w of the sample and the phase coherence length¸P if w(¸P (¸[1]. Therefore, P may be estimated from the correlation "eld B "/w¸P which corresponds to the HWHM of the autocorrelation function of G(B) [1]. This simple relation has been veri"ed for Au and Ag nanowires of widths between 45 and 340 nm [5]. Combining the results of B for samples with the same c but di!erent w, a linear "t B versus w\ gives an estimate for¸P.We calculated a low-"eld (B)3 T) and a high-"eld (B*9.5 T) B for the di!erent samples, yielding¸P (cf. Fig. 2). The large error in¸P is caused by the small number of samples (2}4) for each c as well as an uncertainty in the data analysis due to the restricted "eld range. Furthermore, the simple relation B &¸\ P may be violated by up to 20% in the case of spin}orbit scattering [6].Two reg...

show abstract

Interference and Interaction in Metallic Nanostructures

Weber

2004

CFN Lectures on Functional Nanostructures Vol. 1

View full text Add to dashboard Cite

Geometry dependence of the conductance fluctuations in metallic nanostructures

Cited by 4 publications

References 17 publications

Angular Dependence of Universal Conductance Fluctuations in Noble-Metal Nanowires

Angular Dependence of Universal Conductance Fluctuations in Noble-Metal Nanowires

Universal conductance fluctuations in Cu : Mn nanocontacts

Interference and Interaction in Metallic Nanostructures

Contact Info

Product

Resources

About