Electron Tunneling Study in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>NbSe</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Charge Density Wave State

Sorbier, J.P.; Tortel, Hervé; Monçeau, P.; Lévy, F.

doi:10.1103/physrevlett.76.676

Cited by 26 publications

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“…In NbSe 3 , the measured electrical anisotropy implies a bandwidth in the c direction a factor of 10 larger than in the a direction, qualitatively consistent with band structure calculations [21], so that the former should dominate in tunneling involving the T P2 gap. Analysis of measurements on metal-NbSe 3 tunnel junctions at low biases [8] and of bulk low-temperature thermal and electrical conduction [22] have both suggested a transverse bandwidth comparable to the T P2 gap itself.…”

Section: -2mentioning

confidence: 99%

“…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].…”

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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

et al. 2006

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“…Here, we only show the tunnelling behaviour. Some in-chain tunneling studies have already been made by Sorbier et al [8], but the tunneling peaks due to both upper and lower transitions have only been observed simultaneously in one instance [9], by mechanically placing separate NbSe 3 samples together; mechanical point contacts have been cited as having poor stability and are difficult to produce reliably [2]. Many previous experiments report on tunneling from metal tips perpendicular to the chains along which the CDW wavevector lies, such as in scanning tunneling microscopy experiments [10].…”

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Tunneling spectroscopy in the Charge-Density Wave conductor NbSe₃

et al. 2004

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The motion of Charge-Density Waves (CDWs) shows many similarities with transport in superconductors with the role of voltage and current reversed. Submicron superconducting devices are very important in both fundamental studies and applications of superconductivity. For CDWs, reliable fabrication methods for making similar devices are not as advanced and are still being developed. In search for new mesoscopic CDW physics, we have fabricated insulating longitudinal point contacts and weak links in the CDW conductor NbSe 3. We have found conductance peaks at energies corresponding to the Peierls gap when the temperature is brought below the transitions. The peaks follow a mean-field theory temperature dependence, indicating that the transport through these devices are spectroscopy measurements. The insulating point contacts show tunnelling behaviour similar to SIS junctions, while the weak links show transport similar to SNS junctions. These devices allow us to study the CDW analogies of superconductors such as the Josephson relations, Andeev reflection, subgap features of phonon modes due to electron-phonon coupling and pair-breaking at high velocities.

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“…Until recently tunneling measurements of ⌬ p have been carried out only on NbSe 3 , either using scanning tunneling microscopy ͑STM͒, 2,3 or mechanically fixed tunnel connections. 4,5 In previous cases measurements were mostly performed at 4.2 K and only in the direction along the a axis, i.e., perpendicular to the chain direction. In the present paper we report on point contact spectroscopy of the energy gap in NbSe 3 along the chains.…”

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

et al. 1999

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We have measured the differential current-voltage (IV) characteristics of Au-NbSe 3 point contacts formed in the direction along the conducting chains. We clearly observed charge density wave ͑CDW͒ gap features below the upper Peierls transition temperature in the variation of the differential resistance as a function of bias voltage for a number of contacts with very different zero-bias contact resistances. The temperature dependence of the upper CDW gap, ⌬ p1 , extracted from the data follows the BCS dependence with ⌬ p1 (0)ϭ100 meV, similarly to previous measurements with the current applied perpendicularly to the chains. For contacts with direct conductivity, we found an excess resistance when the applied voltage is less than Ϯ⌬/e. This is attributed to an analog of Andreev reflection, in which the incident electron returns along its original path with its charge unchanged. ͓S0163-1829͑99͒11331-6͔

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Electron Tunneling Study in theNbSe3Charge Density Wave State

Cited by 26 publications

References 16 publications

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

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

Tunneling spectroscopy in the Charge-Density Wave conductor NbSe₃

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

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Electron Tunneling Study in theNbSe3Charge Density Wave State

Cited by 26 publications

References 16 publications

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

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

Tunneling spectroscopy in the Charge-Density Wave conductor NbSe3

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

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Tunneling spectroscopy in the Charge-Density Wave conductor NbSe₃