Latest Research Papers In Condensed Matter Physics | (Cond-Mat.Mes-Hall) 2019-03-01

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Latest Papers in Condensed Matter Physics

Mesoscale And Nanoscale Physics

Topological superconductivity in planar Josephson junctions -- narrowing down to the nanowire limit (1902.11300v1)

F. Setiawan, Ady Stern, Erez Berg

2019-02-28

We theoretically study topological planar Josephson junctions (JJs) formed from spin-orbit-coupled two-dimensional electron gases (2DEGs) proximitized by two superconductors and subjected to an in-plane magnetic field . Compared to previous studies of topological superconductivity in these junctions, here we consider the case where the superconducting leads are narrower than the superconducting coherence length. In this limit the system may be viewed as a proximitized multiband wire, with an additional knob introduced by the phase difference between the superconducting leads. A combination of mirror and time-reversal symmetry may put the system into the class BDI. Breaking this symmetry changes the symmetry class to class D. The class D phase diagram depends strongly on and the chemical potential, with a weaker dependence on . In contrast, the class BDI phase diagram depends strongly on both and . Interestingly, the BDI phase diagram has a "fan"-shaped region with phase boundaries which move away from linearly with . The number of distinct phases in the fan increases with increasing chemical potential. We study the dependence of the JJ's critical current on , and find that minima in the critical current indicate first-order phase transitions in the junction only when the spin-orbit coupling strength is small. In contrast to the case of a JJ with wide leads, in the narrow case these transitions are not accompanied by a change in the JJ's topological index. Our results, calculated using realistic experimental parameters, provide guidelines for present and future searches for topological superconductivity in JJs with narrow leads, and are particularly relevant to recent experiments on InAs 2DEGs proximitized by narrow Al superconducting leads (A. Fornieri et al., arXiv:1809.03037).

Full counting statistics of trapped ballistic electrons (1902.11253v1)

L. Freise, T. Gerster, D. Reifert, T. Weimann, K. Pierz, F. Hohls, N. Ubbelohde

2019-02-28

We demonstrate the trapping of ballistic non-equilibrium electrons, introducing the capability of near-deterministic single-electron circuitry to electron quantum optics. Single-electron detection of on-demand generated electrons resolves the full counting statistics of the circuit's outcome, with a maximal overall-fidelity of 0.996. Trapping the electrons by energy-dependent barriers includes the capability to assess the energetic and arrival-time distributions of single electron wave packets and resolves additional excitation products.

Quantization of the Vibrations of a Thin Elastic Plate (1902.11252v1)

Eliot Heinrich, Dennis P. Clougherty

2019-02-28

Suspended thin films have been successfully used as high-Q mechanical oscillators in hybrid optomechanical systems to study fundamental quantum mechanical effects. Motivated by these experiments, we consider a Hamiltonian description of the vibrations of a clamped, elastic circular plate. The Hamiltonian of this system features a potential energy with two distinct contributions: one that depends on the local mean curvature of the plate, and a second one that depends on its Gaussian curvature. We quantize this model using a complete, orthonormal set of eigenfunctions for the clamped, vibrating plate. The resulting quanta are the flexural phonons of the thin circular plate. As an application, we use this quantized description to calculate the fluctuations in displacement of the plate's center for arbitrary temperature.

Majorana Bound States in Double Nanowires with Reduced Zeeman Thresholds due to Supercurrents (1902.11232v1)

Olesia Dmytruk, Manisha Thakurathi, Daniel Loss, Jelena Klinovaja

2019-02-28

We study the topological phase diagram of a setup composed of two nanowires with strong Rashba spin-orbit interaction subjected to an external magnetic field and brought into the proximity to a bulk -wave superconductor in the presence of a supercurrent flowing through it. The supercurrent reduces the critical values of the Zeeman energy and crossed Andreev superconducting pairing required to reach the topological phase characterized by the presence of one Majorana bound state localized at each system end. We demonstrate that, even in the regime of the crossed Andreev pairing being smaller than the direct proximity pairing, a relatively weak magnetic field drives the system into the topological phase due to the presence of the supercurrent.

Valley-Chern Effect with LC-Resonators: A Modular Platform (1810.11578v2)

Yishai Eisenberg, Yafis Barlas, Emil Prodan

2018-10-27

The valley Chern-effect is theoretically demonstrated with a novel alternating current circuitry, where closed-loop LC-resonators sitting at the nodes of a honeycomb lattice are inductively coupled along the bonds. This enables us to generate a dynamical matrix which copies identically the Hamiltonian driving the electrons in graphene. The valley-Chern effect is generated by splitting the inversion symmetry of the lattice. After a detailed study of the Berry curvature landscape and of the localization of the interface modes, we derive an optimal configuration of the circuit. Furthermore, we show that Q-factors as high as can be achieved with reasonable materials and configurations.