Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFinite Size Effect in Amorphous Indium oxide
240
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study the low temperature magneto-transport properties of several highly disordered amorphous Indium oxide(a:InO) samples. Simultaneously fabricated devices comprising a 2-dimensional (2D) film and 10 $mu$m long wires of different widths were measured to investigate the effect of size as we approach the 1D limit, which is around 4 times the correlation length, and happens to be around 100 nm for a:InO. The film and the wires showed magnetic field ({it B}) induced superconductor to insulator transition (SIT). In the superconducting side, the resistance increased with decrease in wire width, whereas, an opposite trend is observed in the insulating side. We find that this effect can be explained in light of charge-vortex duality picture of the SIT. Resistance of the 2D film follows an activated behavior over the temperature ($T$), whereas, the wires show a crossover from the high-$T$ activated to a $T$-independent behavior. At high temperature regime the wires resistance follow the films until they deviate and became independent of $T$. We find that temperature at which this deviation occurs evolve with magnetic field and the width of the wire, which show the effect of finite size on the transport.
rate research
Read More
We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The $R(T)$ broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions.
Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime. Thus far, experimental studies of MZMs chiefly relied on single electron tunneling measurements which leads to decoherence of the quantum information stored in the MZM. As a next step towards topological quantum computation, charge parity conserving experiments based on the Josephson effect are required, which can also help exclude suggested non-topological origins of the zero bias conductance anomaly. Here we report the direct measurement of the Josephson radiation frequency in InAs nanowires with epitaxial aluminium shells. For the first time, we observe the $4pi$-periodic Josephson effect above a magnetic field of $approx 200,$mT, consistent with the estimated and measured topological phase transition of similar devices.
We report large-scale simulations of the resistively-shunted Josephson junction array in strip geometry. As the strip width increases, the voltage first decreases following the dynamic scaling ansatz proposed by Minnhagen {it et al.} [Phys. Rev. Lett. {bf 74}, 3672 (1995)], and then rises towards the asymptotic value predicted by Ambegaokar {it et al.} [Phys. Rev. Lett. {bf 40}, 783 (1978)]. The nonmonotonic size-dependence is attributed to shortened life time of free vortices in narrow strips, and points to the danger of single-scale analysis applied to a charge-neutral superfluid state.
We investigate theoretically the simultaneous tunneling of two electrons from a superconductor into a normal metal at low temperatures and voltages. Such an emission process is shown to be equivalent to the Andreev reflection of an incident hole. We obtain a local tunneling Hamiltonian that permits to investigate transport through interfaces of arbitrary geometry and potential barrier shapes. We prove that the bilinear momentum dependence of the low-energy tunneling matrix element translates into a real space Hamiltonian involving the normal derivatives of the electron fields in each electrode. The angular distribution of the electron current as it is emitted into the normal metal is analyzed for various experimental setups. We show that, in a full three-dimensional problem, the neglect of the momentum dependence of tunneling causes a violation of unitarity and leads to the wrong thermodynamic (broad interface) limit. More importantly for current research on quantum information devices, in the case of an interface made of two narrow tunneling contacts separated by a distance $r$, the assumption of momentum-independent hopping yields a nonlocally entangled electron current that decays with a prefactor proportional to $r^{-2}$ instead of the correct $r^{-4}$.
We study a current shot noise in a macroscopic insulator based on a two-dimensional electron system in GaAs in a variable range hopping (VRH) regime. At low temperature and in a sufficiently depleted sample a shot noise close to a full Poissonian value is measured. This suggests an observation of a finite-size effect in shot noise in the VRH conduction and demonstrates a possibility of accurate quasiparticle charge measurements in the insulating regime.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
