Suppression of Coulomb blockade peaks by electronic correlations in InAs nanowires

Abstract

We performed electronic transport measurements on 1D InAs quantum wires. In sufficiently disordered wires, transport is dominated by Coulomb blockade, and the conductance can be well described by tunneling through a quantum dot embedded between two one-dimensional Luttinger liquid wires. In contrast to previous experiments in other material systems, in our system the conductance difference between peak to valley decreases with decreasing temperature for several consecutive peaks. This phenomenon is theoretically expected to occur only for strongly interacting systems with small Luttinger interaction parameter g < 1/2; we find for our InAs wires a value of g ≈ 0.4. Possible mechanisms leading to these strong correlations are discussed.PACS numbers: 73.23. Hk, 73.21.Hb, 71.10.Pm Extensive theoretical [1,2] and experimental [3][4][5] research has been devoted to one-dimensional (1D) InAs and InSb semiconductor nanowires (NWs) over the past few years. Such NWs, when put in proximity to a superconductor, are expected to host Majorana topological states due to strong spin-orbit coupling. The lack of a Schottky barrier with the metallic contact and the relatively large Landé factor make the experimental conditions for observing these exotic topological states quite feasible. Indeed, a zero bias peak as a signature of Majorana states was reported in InSb [4,5] and InAs [3] NWs in proximity to superconducting Nb and Al films, respectively.One of the main features in such 1D wires is the existence of ballistic helical states which are theoretically predicted [6] to exhibit nonmonotonic (up and down) conductance steps of size G 0 = e 2 /h as the electron density is varied by the gate voltage. Although many attempts have been made to measure these conductance steps, they have not been observed yet in either InAs or InSb NWs. This indicates that disorder plays an essential role, preventing the motion of the electrons between the contacts from being ballistic. It is well known that in 1D electronelectron interactions, described by the Luttinger-liquid (LL) model, amplify the role of disorder significantly, causing the conductance to vanish at zero temperature even for very weak disorder [7]. Experimentally, however, the effects of the interactions in NWs with strong spin-orbital scattering have not yet been reported.In this letter we report on experimental studies of electronic transport in disordered InAs NW at low temperatures over a wide range of electron densities. At very low densities we find the transport to be governed by Coulomb blockade, and at relatively high electron density by sequential tunneling through a series of barriers present in the disordered NW. We demonstrate that in both regimes the conductance is strongly affected by electron-electron interactions. The analysis of the temperature dependence of the conductance and of the line shape of the resonant tunneling in the Coulomb blockade regime within the framework of the existing theories [7] allows us to deduce the corresponding LL parameter g. We show ...

Dynamic response functions and helical gaps in interacting Rashba nanowires with and without magnetic fields

“…We find that whereas a magnetic field perpendicular to the Rashba axis always opens a partial gap in the spectrum, it is only for sufficiently strong interactions, characterized by a Luttinger parameter K < 1/2, that spin-umklapp scattering can open a similar gap, provided the chemical potential is tuned close to the Dirac point. However, such strong interactions (K ∼ 0.2 − 0.4) have been observed in semiconductor nanowires 27,28 and carbon nanotubes. 29 As both a perpendicular magnetic field and spin-umklapp scattering open a partial gap, we must conceive of a means of telling them apart.…”

Missing Shapiro steps and the 8π -periodic Josephson effect in interacting helical electron systems

“…43 We would like to point out that the required strong interactions have already been seen in these wires. 44 Umklapp scattering has also recently been invoked to explain the reduction in conductance observed in InAs/GaSb topological insulator edge states. 60 Introducing a weak superconducting proximity effect in either these wires or edge states will then lead to the creation of bound states and allow the observation of the 8π periodic Josephson current component.…”

Strong electron-electron interactions of a Tomonaga-Luttinger liquid observed in InAs quantum wires

“…Despite active discussions in theory, there are only few experimental results about TLL physics in wires with strong SOIs. Concerning InAs, we note the self-assembled nanowires [31] and nanowire quantum point contacts [32] experiments. In the former, a small interaction parameter was deduced, but it remained unclear whether this was due to the SOIs, or intrinsically strong e-e interactions, or even some other physics.…”