Nonsymmetrized Correlations in Quantum Noninvasive Measurements

A long-standing problem in quantum mesoscopic physics is which operator order corresponds to noise expressions like , where I(\omega) is the measured current at frequency \omega. Symmetrized order describes a classical measurement while nonsymmetrized order corresponds to a quantum detector, e.g., one sensitive to either emission or absorption of photons. We show that both order schemes can be embedded in quantum weak-measurement theory taking into account measurements with memory, characterized by a memory function which is independent of a particular experimental detection scheme. We discuss the resulting quasiprobabilities for different detector temperatures and how their negativity can be tested on the level of second-order correlation functions already. Experimentally, this negativity can be related to the squeezing of the many-body state of the transported electrons in an ac-driven tunnel junction.Comment: 5+2 pages, 1 figur

Interferometric and noise signatures of Majorana fermion edge states in transport experiments

Domain walls between superconducting and magnetic regions placed on top of a topological insulator support transport channels for Majorana fermions. We propose to study noise correlations in a Hanbury Brown-Twiss type interferometer and find three signatures of the Majorana nature of the channels. First, the average charge current in the outgoing leads vanishes. Furthermore, we predict an anomalously large shot noise in the output ports for a vanishing average current signal. Adding a quantum point contact to the setup, we find a surprising absence of partition noise which can be traced back to the Majorana nature of the carriers.Comment: 5 pages, 2 figure

Full counting statistics of Majorana interferometers

We study the full counting statistics of interferometers for chiral Majorana fermions with two incoming and two outgoing Dirac fermion channels. In the absence of interactions, the FCS can be obtained from the $4\times4$ scattering matrix $S$ that relates the outgoing Dirac fermions to the incoming Dirac fermions. After presenting explicit expressions for the higher-order current correlations for a modified Hanbury Brown-Twiss interferometer, we note that the cumulant-generating function can be interpreted such that unit-charge transfer processes correspond to two independent half-charge transfer processes, or alternatively, to two independent electron-hole conversion processes. By a combination of analytical and numerical approaches, we verify that this factorization property holds for a general $SO(4)$ scattering matrix, i.e. for a general interferometer geometry.Comment: 22 pages, 3 figures, contributed to the special issue of Physica E "Frontiers in Quantum Electronic Transport - In Memory of Markus Buttiker

Signatures of the Higgs mode in transport through a normal-metal--superconductor junction

A superconductor subject to electromagnetic irradiation in the terahertz range can show amplitude oscillations of its order parameter. However, coupling this so-called Higgs mode to the charge current is notoriously difficult. We propose to achieve such a coupling in a particle-hole-asymmetric configuration using a DC-voltage-biased normal-metal--superconductor tunnel junction. Using the quasiclassical Green's function formalism, we demonstrate three characteristic signatures of the Higgs mode: (i) The AC charge current exhibits a pronounced resonant behavior and is maximal when the radiation frequency coincides with the order parameter. (ii) The AC charge current amplitude exhibits a characteristic nonmonotonic behavior with increasing voltage bias. (iii) At resonance for large voltage bias, the AC current vanishes inversely proportional to the bias. These signatures provide an electric detection scheme for the Higgs mode.Comment: 5.2+3 page

Dislocation and grain boundary interaction in oxides: Slip transmission or cracking?

Please click Additional Files below to see the full abstract

Artefakte im Altquartär von Obergaliläa (Nordisrael)

Bei Yiron treten auf Karbonatgesteinen der Oberkreide und des Alttertiärs tonige Bodensedimente auf. Lokal ist darin ein Kalk- und Flintschotter eingeschaltet, der altpaläolithische Artefakte führt. Ein inzwischen erosiv aufgelöster revers magnetisierter Deckbasalt bildet das Hangende. Er ist zum damals bereits angelegten Jordan-Graben hin orientiert. Die Artefakte müssen demnach älter sein als die Brunhes-Matuyama-Grenze. Sie gehören neben den Funden von Evron (nördlich Haifa) und Ubaidiya (Jordan-Graben) zu den ältesten Hinterlassenschaften des Menschen im Vorderen Orient. Ferner liegt eine ebenfalls relativ alte Faustkeil-Kultur auf den Plateaus von Yiron und Baram. Die Plateaus von Yiron und Baram lassen sich in geomorphologischer Hinsicht als ein flaches Hochtal interpretieren. Die weitere Entwicklung ist durch eine Kerbtal-Bildung gekennzeichnet.researc

Diamagnetic response of cylindrical normal metal - superconductor proximity structures with low concentration of scattering centers

We have investigated the diamagnetic response of composite NS proximity wires, consisting of a clean silver or copper coating, in good electrical contact to a superconducting niobium or tantalum core. The samples show strong induced diamagnetism in the normal layer, resulting in a nearly complete Meissner screening at low temperatures. The temperature dependence of the linear diamagnetic susceptibility data is successfully described by the quasiclassical Eilenberger theory including elastic scattering characterised by a mean free path l. Using the mean free path as the only fit parameter we found values of l in the range 0.1-1 of the normal metal layer thickness d_N, which are in rough agreement with the ones obtained from residual resistivity measurements. The fits are satisfactory over the whole temperature range between 5 mK and 7 K for values of d_N varying between 1.6 my m and 30 my m. Although a finite mean free path is necessary to correctly describe the temperature dependence of the linear response diamagnetic susceptibility, the measured breakdown fields in the nonlinear regime follow the temperature and thickness dependence given by the clean limit theory. However, there is a discrepancy in the absolute values. We argue that in order to reach quantitative agreement one needs to take into account the mean free path from the fits of the linear response. [PACS numbers: 74.50.+r, 74.80.-g]Comment: 10 pages, 9 figure