Point-contact spectroscopy of the charge-density-wave gap along the chains in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">NbSe</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Синченко, А. А.; Latyshev, Yu. I.; Зыбцев, С. Г.; Gorlova, I. G.; Monçeau, P.

doi:10.1103/physrevb.60.4624

Cited by 26 publications

(22 citation statements)

References 13 publications

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“…Crossed NbSe 3 -NbSe 3 crystals [9] yield peak voltages of 60 mV and 142 mV, and interlayer tunneling in microfabricated NbSe 3 mesas yields peaks at 50 mV and 120 mV [3]. A single in-chain tunneling study [2] using a gold ribbon mechanically positioned near the end of a NbSe 3 crystal gave a peak at 100 mV for the T P1 CDW.…”

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In-Chain Tunneling through Charge-Density-Wave Nanoconstrictions and Break Junctions

et al. 2006

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We have fabricated longitudinal nanoconstrictions in the charge-density wave conductor (CDW) NbSe 3 using a focused ion beam and using a mechanically controlled break-junction technique. Conductance peaks are observed below the T P1 145 K and T P2 59 K CDW transitions, which correspond closely with previous values of the full CDW gaps 2 1 and 2 2 obtained from photoemission. These results can be explained by assuming CDW-CDW tunneling in the presence of an energy gap corrugation 2 comparable to 2 , which eliminates expected peaks at j 1 2 j. The nanometer length scales our experiments imply indicate that an alternative explanation based on tunneling through back-to-back CDW-normal-conductor junctions is unlikely. DOI: 10.1103/PhysRevLett.96.096402 PACS numbers: 71.45.Lr, 73.23.ÿb, 73.40.Gk, 74.50.+r Charge-density wave (CDW) conduction remains of major interest despite its experimental discovery nearly 30 years ago. Much of the existing work has focused on transport properties of as-grown single crystals [1]. More recently, micro-and nanofabrication methods for CDW materials has allowed the study of mesoscopic CDW physics [2 -4]. Structures for tunneling spectroscopy are of particular interest because of the unusual gap structure with large one-dimensional fluctuation effects expected in these highly anisotropic materials, and because of predictions of unusual midgap excitations of the collective mode [5]. Tunneling studies in fully gapped CDW conductors like the ''blue bronze'' K 0:3 MoO 3 suffer from band-bending effects at the interface akin to semiconductor-insulatormetal junctions. These effects are absent in the partially gapped CDW conductor NbSe 3 , which remains metallic down to 4.2 K.Tunneling perpendicular to the direction b of the quasione-dimensional chains, along which the CDW wave vector lies, has been studied in ribbonlike whiskers of NbSe 3 by scanning tunneling microscopy (STM) [6], by tunneling through Pb contacts evaporated over the native oxide on the b-c plane [7,8], and by tunneling through a gold wire or a NbSe 3 crystal that is laid across another NbSe 3 crystal, forming junctions in the a-b or b-c planes [9,10]. Peaks in the T 4:2 K differential conductance at 35 and 101 mV [6], 35 mV [7], 36 mV and 90 mV [9], and 37 mV and 100 mV [10] from metal-NbSe 3 junctions correspond well with the CDW gaps 1 110 mV and 2 45 mV for NbSe 3 's T P1 145 K and T P2 59 K CDWs as determined by angle-resolved photo emission (ARPES) [11]. Crossed NbSe 3 -NbSe 3 crystals [9] yield peak voltages of 60 mV and 142 mV, and interlayer tunneling in microfabricated NbSe 3 mesas yields peaks at 50 mV and 120 mV [3]. A single in-chain tunneling study [2] using a gold ribbon mechanically positioned near the end of a NbSe 3 crystal gave a peak at 100 mV for the T P1 CDW.Here we demonstrate that a small constriction in a NbSe 3 single crystal, produced by dry etching with a Ga focused ion beam (FIB), shows conductance peaks at 105 mV and 190 mV corresponding to 2 1 and 2 2 , as illustrated in Fig. 1. We reproduce ...

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In-Chain Tunneling through Charge-Density-Wave Nanoconstrictions and Break Junctions

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“…8 Electrical contacts that inject the current parallel to the CDW chains allow detailed studies of the subgap conductance. 9 In this paper we report characteristic effects of weak localization on CDW sliding through a disordered conductor. In contrast to the extensive literature on semiconductor-or superconductor hybrid structures, 1 this topic has, to the best of our knowledge, not yet been investigated.…”

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Strong effects of weak localization in charge-density-wave/normal-metal hybrids

2000

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Collective transport through a multichannel disordered conductor in contact with charge-density-wave electrodes is theoretically investigated. The statistical distribution function of the threshold potential for chargedensity-wave sliding is calculated by random matrix theory. In the diffusive regime weak localization has a strong effect on the sliding motion.Wave ͑Anderson͒ localization is an important concept of the quantum theory of electron transport. It is well established by now that a random disorder potential may cause bound states with an exponential decay governed by the localization length. When this localization length is large compared to other length scales in the system, the corrections to semiclassical transport are small, and the term ''weak localization'' is appropriate. Weak localization is well understood for normal Fermi liquids. However, localization in heterostructures like superconducting metal/normal metal ͑S/N͒, or Josephson ͑S/N/S͒ junctions is still actively investigated, experimentally and theoretically. For example, the electronhole coherence induced in a normal metal by a superconducting reservoir significantly modifies the weak localization correction to the electron transport through the hybrid structure. 1A charge-density wave ͑CDW͒ is a collective state similar to BCS superconductors ͑S͒.2 For instance, CDW reservoirs induce a proximity effect in normal metals ͑N͒ analogous to that in N/S junctions when the interface is parallel to the CD wave fronts ͑normal to the chains͒. In such a geometry the phase coupling through a defect-free CDW/N/CDW junction supports a sliding CDW mode.3 A process analogous to Andreev scattering at an N/CDW interface has been predicted. 4 Advances in thin film growth and patterning of CDW compounds 5 enables the study of CDW transport in various geometries on a mesoscopic scale.6,7 Quantum oscillations have been identified in the magnetoresistance of the CDW compound NbSe 3 in the presence of columnar defects.8 Electrical contacts that inject the current parallel to the CDW chains allow detailed studies of the subgap conductance. 9In this paper we report characteristic effects of weak localization on CDW sliding through a disordered conductor. In contrast to the extensive literature on semiconductor-or superconductor hybrid structures, 1 this topic has, to the best of our knowledge, not yet been investigated. The statistical properties of diffuse conductors, including the weaklocalization correction to the average conductance, are well described by random matrix theory. 10 We calculate the statistical properties of the pinning energy in the presence and absence of time-reversal symmetry by averaging over random transfer matrices. We find that the pinning strength is much more sensitive to the localization-enhanced backward scattering than the normal conductance. Weak localization is destroyed when time reversal-symmetry is broken by a magnetic field, 11 leading to a substantial negative magnetoresistance.We consider a disordered metal with length L an...

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“…1, coincides with the 2⌬ p2 / e value known from former works. [24][25][26][27][28] At the same time, independent of the contact resistance, all the curves qualitatively show a similar behavior at ͉V͉ Ͼ 50 mV, demonstrating a characteristic minimum at ͉V͉ = 80-92 mV, the mean value of which ͑88.9 mV͒ is closely related to the value of the high-temperature CDW energy gap ⌬ p1 . 28 Note that, in spite of the significant difference in the resistance values at V =0 ͑3 orders of magnitude͒, the positions of the energy gap singularities appear within a relatively small voltage dispersion, demonstrating the good reproducibility of the experimental data.…”

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Coherent-noncoherent tunneling crossover inNbSe3−NbSe3point contacts

Синченко

Monçeau

2007

Phys. Rev. B

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Current-voltage ͑IV͒ characteristics of NbSe 3 -NbSe 3 artificial contacts ͑point contacts͒ formed along the a * axis have been investigated in a wide range of contact resistances and temperatures. Depending on the contact resistance, two types of IV characteristics have been observed: the first type observed for low contact resistance demonstrates a conducting peak at zero bias, while the second one for large contact resistance is characterized by a large resistance maximum near the zero bias voltage. Below the second charge-density wave ͑CDW͒ transition ͑T Ͻ 59 K͒, CDW energy gap singularities were observed in the IV characteristics of both types of junctions at V = ⌬ p1 / e and V =2⌬ p2 / e, while the singularity at V = ⌬ p2 / e corresponding to the single particle tunneling of carriers noncondensed into the low-temperature CDW is absent. The experimental results are discussed in the frame of the model of interlayer coherent tunneling of the remaining charge carriers that are not condensed into the CDW.

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Point-contact spectroscopy of the charge-density-wave gap along the chains inNbSe3

Cited by 26 publications

References 13 publications

In-Chain Tunneling through Charge-Density-Wave Nanoconstrictions and Break Junctions

In-Chain Tunneling through Charge-Density-Wave Nanoconstrictions and Break Junctions

Strong effects of weak localization in charge-density-wave/normal-metal hybrids

Coherent-noncoherent tunneling crossover inNbSe3−NbSe3point contacts

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