(24). Single-crystal films are essential for devices based on superconductor, giant magnetoresistance, thermionic, piezoelectric, and ferroelectric metal oxides because the intrinsic properties of the material, rather than its grain boundaries, can be exploited. The most active crystallographic orientation can also be selected. Our results show that epitaxy can be achieved even for systems with very high lattice mismatch, and they provide a method for producing other nonequilibrium phases that cannot be accessed by traditional thermal processing. Golden, ibid. 258, 1918Golden, ibid. 258, (1992. 3. J. A. Switzer et al., ibid. 264, 1573Switzer et al., ibid. 264, (1994 A Hanbury Brown and Twiss experiment for a beam of electrons has been realized in a two-dimensional electron gas in the quantum Hall regime. A metallic split gate serves as a tunable beam splitter to partition the incident beam into transmitted and reflected partial beams. In the nonequilibrium case the fluctuations in the partial beams are shown to be fully anticorrelated, demonstrating that fermions exclude each other. In equilibrium, the crosscorrelation of current fluctuations at two different contacts is also found to be negative and nonzero, provided that a direct transmission exists between the contacts.

We have measured the current(I)-voltage(V ) characteristics of a single-wall carbon nanotube quantum dot coupled to superconducting source and drain contacts in the intermediate coupling regime. Whereas the enhanced differential conductance dI/dV due to the Kondo resonance is observed in the normal state, this feature around zero bias voltage is absent in the superconducting state. Nonetheless, a pronounced even-odd effect appears at finite bias in the dI/dV sub-gap structure caused by Andreev reflection. The first-order Andreev peak appearing around V = ∆/e is markedly enhanced in gate-voltage regions, in which the charge state of the quantum dot is odd. This enhancement is explained by a 'hidden' Kondo resonance, pinned to one contact only. A comparison with a single-impurity Anderson model, which is solved numerically in a slave-boson meanfield ansatz, yields good agreement with the experiment. There is a growing interest in the exploration of correlated charge transport through nanoscaled lowdimensional systems involving both superconductors and normal metals [1,2,3,4,5,6]. The penetration of the pair amplitude ∆ from a superconductor (S) into a normal metal (N), the proximity effect, is a manifestation of correlated charge transport mediated by Andreev processes taking place at the S-N interface [7] and leading in S-N-S junctions to the Josephson effect [8] and sup-gap current peaks due to multiple Andreev reflection (MAR) [9]. The superconducting proximity effect has been studied in great detail in the mesoscopic size regime of diffusive, but phase coherent conductors [10]. Andreev transport has also been the key quantity in experiments elucidating charge transport in single atom contacts [5,11]. On the other hand, Andreev transport through a quantum dot coupled to superconductors, is just emerging now [12,13,14,15]. If the dot is weakly coupled to the leads, Andreev processes are suppressed by the charging energy U of the dot [3,16,17]. If the dot is sufficiently small, size quantization takes place, forming a quantum dot (QD) with discrete eigenstates ('levels') at energies E {i} . Transport then occurs through individual levels [3]. Since the level 'positions' E {i} , and sometimes also the coupling strengths of the levels to both source and drain contacts Γ 1,2 , can be tuned through gate voltages, a physically tunable model system of the Anderson 'impurity problem' is realized. With one electron on the QD (half-filling), a many-electron ground-state forms, involving both the dot-state and conduction electrons from the leads in an energy window given by the the Kondo temperature T K [18,19].

We report low-temperature shot noise measurements of short diffusive Au wires attached to electron reservoirs of varying sizes. The measured noise suppression factor compared to the classical noise value 2e |I| strongly depends on the electric heat conductance of the reservoirs. For small reservoirs injection of hot electrons increases the measured noise and hence the suppression factor. The universal 1/3-suppression factor can only asymptotically be reached for macroscopically large and thick electron reservoirs. A heating model based on the Wiedemann-Franz law is used to explain this effect. 73.50.Td, 72.70.+m, Typeset using REVT E X 1

The discreteness of charge in units of e led Schottky in 1918 to predict that the electrical current in a vacuum tube fluctuates even if all spurious noise sources are eliminated carefully. This phenomenon is now widely known as shot noise. In recent years, shot noise in mesoscopic conductors, where charge motion is quantum-coherent over distances comparable to the system size, has been studied extensively. In those experiments, charge does not propagate as an isolated entity through free space, as for vacuum tubes, but is part of a degenerate and quantum-coherent Fermi sea of charges. It has been predicted that shot noise in mesoscopic conductors can disappear altogether when the system is tuned to a regime where electron motion becomes classically chaotic. Here we experimentally verify this prediction by using chaotic cavities where the time that electrons dwell inside can be tuned. Shot noise is present for large dwell times, where the electron motion through the cavity is 'smeared' by quantum scattering, and it disappears for short dwell times, when the motion becomes classically deterministic.

We have experimentally studied shot noise of chaotic cavities defined by two quantum point contacts in series. The cavity noise is determined as ͑1͞4͒2ejIj in agreement with theory and can be well distinguished from other contributions to noise generated at the contacts. Subsequently, we have found that cavity noise decreases if one of the contacts is further opened and reaches nearly zero for a highly asymmetric cavity. Heating inside the cavity due to electron-electron interaction can slightly enhance the noise of large cavities and is also discussed quantitatively.