Transport properties of ultrathin Pd films

Liu, Y.; Price, John C.

doi:10.1016/0921-4526(94)91005-7

Cited by 4 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In Josephson junction arrays with ultra-small junctions [18] and Pd films [19], nonlinear behavior at high resistances has been attributed to effects related to the charge Kosterlitz Thouless Berezinskii (KTB) transition. As a consequence of the electrical duality between the charge and vortex KTB transitions [20], nonlinear I-V characteristics would be expected, with I ∝ V a , and a exhibiting a jump from 1 to 3 at the transition temperature.…”

mentioning

confidence: 99%

Evidence of Collective Charge Behavior in the Insulating State of Ultrathin Films of Superconducting Metals

2002

View full text Add to dashboard Cite

Nonlinear I-V characteristics have been observed in insulating quench-condensed films which are locally superconducting. We suggest an interpretation in terms of the enhancement of conduction by the depinning of a Cooper pair charge density wave, Cooper pair crystal, or Cooper pair glass that may characterize the insulating regime of locally superconducting films. We propose that this is a more likely description than the Coulomb blockade or charge-anticharge unbinding phenomena.In the context of the Bose-Hubbard model, which is equivalent to the model of a Josephson junction array with charging, zero-temperature superconductorinsulator(SI) transitions in two dimensions (2D), tuned by disorder or magnetic field, are believed to be direct, with metallic behavior only at the quantum critical point [1]. Recent experiments have suggested the existence of a significant metallic phase between the superconductor and insulator. The Stanford group reported this for nominally superconducting MoGe films in moderate magnetic fields at low temperatures, and conjectured that it was due to dissipation [2]. They later found "true" superconductivity in low fields [3]. Long ago, metallic behavior was reported in quench-condensed granular films over a range of thicknesses intermediate between those for which films were insulating and superconducting [4], and it was found more recently in Josephson junction arrays [5]. Re-examination of the theory has involved the inclusion of aspects of percolation [6], elaboration of the Bose-Hubbard model [7,8], and consideration of dissipative Bose systems [9]. Das and Doniach [7] explained aspects of Ref. 4 by extending the Bose-Hubbard model to high filling and including nearest-neighbor as well as on-site Coulomb interactions. Their phase diagram contains the possibility of an intervening Bose metal phase, or a direct transition, depending upon the relative magnitudes of the various Coulomb and Josephson coupling energies. The Bose metal contains free vortices and antivortices, prevented from Bose condensing by dissipation. The insulator is a condensate of vortices, or in other language, a Cooper pair charge density wave (CDW). Phillips and Dalidovich [8], using the original form of the Bose-Hubbard model, also demonstrated that there was a Bose metallic phase. This followed from a subtle cancellation in the expression for the conductivity between an exponentially small population of bosonic quasiparticles and their associated exponentially long scattering time. The Bose insulator in this picture results from dissipative processes such as coupling to a heat bath, or from a high enough level of disorder. Ng and Lee [9], using a different approach to theory of dissipative Bose systems, suggest that a Bose metal does not exist at zero temperature, but note a crossover regime at finite temperature that could be identified as a metallic phase.In this letter we shift the focus to the study of the insulating regime of granular quench-condensed films. In the past the insulator has not been carefully...

show abstract

mentioning

confidence: 99%

Evidence of Collective Charge Behavior in the Insulating State of Ultrathin Films of Superconducting Metals

2002

View full text Add to dashboard Cite

show abstract

“…In subfilm (12), the both layers are in identical dynamical situation and there the transition temperatures are the same.…”

Section: Resultsmentioning

confidence: 85%

“…It was shown that there exist only two type of excitations distributed on two layers. Only subfilms (01), (12) and (23) were analyzed, and this is done consistently in the nearest neighbor appoximation. It was shown that the subfilms (01) and (12) are not dynamically identical.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

The Green's Functions of Spatially Confined Order-Disorder Systems

Garić

Obadović

Tošić

et al. 2004

Int. J. Mod. Phys. B

View full text Add to dashboard Cite

The theory of Green's functions (GF) for thin films was formulated, where site indices were different also along the direction of broken symmetry. This approach results in the layer dependence of correlation functions in films, which did not appear in the previous investigations of thin films. The magnetizations of three layer thin ferromagnetic (FM) and four layer thin ferroelectric (FE) films were investigated using the GFs found in this way. It was shown that the transition temperature varies from layer to layer, which is the obvious consequence of the generalization of the formalism of the GF calculation for films.

show abstract

“…In Josephson junction arrays with ultra-small junctions [16] and Pd films [17] nonlinear behavior at high resistances has been attributed to effects related to the charge Kosterlitz-Thouless-Berezinskii (KTB) transition which is the electrical dual of the vortex KTB transition [18]. This model is irrelevant because the phys.…”

mentioning

confidence: 99%

Nonlinear Current-Voltage Characteristics of Locally Superconducting Elemental Films

Christiansen

Hernández

Goldman³

2002

phys. stat. sol. (b)

View full text Add to dashboard Cite

Subject classification: 71.30.þh; 74.25.Dw; 74.76.Db; 74.80.Bj; S4 Nonlinear I-V characteristics have been observed in quench-condensed films which are locally superconducting. We suggest an interpretation of an apparent threshold phenomenon in terms of the enhancement of conduction by the depinning of a charge structure that may characterize this insulating regime. We propose that this is a more likely description than Coulomb blockade or charge-anticharge unbinding phenomena.In the context of the Bose-Hubbard model, zero-temperature superconductor-insulator (SI) transitions in two dimensions (2D), tuned by disorder or magnetic field, are direct, with metallic behavior only at a quantum critical point [1]. Recent experiments suggest that there may be a metallic phase separating the superconductor and insulator. This was observed in MoGe films at moderate magnetic fields at low temperatures, and attributed to dissipation [2]. A transition to "true" superconductivity was reported at low field [3]. It is well known that metallic behavior is found in quench-condensed granular films over a range of thicknesses intermediate between those for which films are insulating and superconducting [4]. Similar observations have been made for Josephson junction arrays [5]. Several new approaches to theory have yielded a metallic phase [6][7][8].Here our concern is with the insulating regime of granular quench-condensed films, which exhibit superconducting, metallic and insulating behaviors. In the past neither the insulating, nor the metallic regimes were the focus of investigation, as the main issue was determining the onset of superconductivity. Since local superconductivity exists in granular films when they are not globally superconducting [10] they should be good candidates for the application of the Bose-Hubbard model, in which there is nonvanishing order parameter amplitude. We focus on Ga films, which earlier exhibited the most striking metallic regime [4]. We propose that the nonlinear I-V characteristics found in the insulating regime may be evidence of a Bose insulating state, which could be either a Cooper-pair CDW, Cooper pair crystal, or for sufficient disorder, a Cooper pair glass. The nonlinearities are similar to those found in the depinning of charge density waves by a current [11]. The behavior of these films is different from that of nominally homogeneous films, where an orbital magnetoresistance linear in field was interpreted as evidence of vortices [12].Gallium films were grown on glazed alumina substrates held at liquid helium temperatures. This was done in an ultra high vacuum apparatus in which cyclic evaporations and in situ transport measurements [13] at temperatures down to 150 mK could be made.We show in Fig. 1 the evolution of RðTÞ with thickness of a-Ga films, adapted from Ref. [4]. The evidence for local superconductivity is the local minimum of RðTÞ.

show abstract

Transport properties of ultrathin Pd films

Cited by 4 publications

References 4 publications

Evidence of Collective Charge Behavior in the Insulating State of Ultrathin Films of Superconducting Metals

Evidence of Collective Charge Behavior in the Insulating State of Ultrathin Films of Superconducting Metals

The Green's Functions of Spatially Confined Order-Disorder Systems

Nonlinear Current-Voltage Characteristics of Locally Superconducting Elemental Films

Contact Info

Product

Resources

About