Loss and Decoherence at the Quantum Hall-Superconductor Interface

Lingfei Zhao, Zubair Iftikhar, Trevyn F. Q. Larson, Ethan G. Arnault, Kenji Watanabe, Takashi Taniguchi, François Amet, and Gleb Finkelstein

Phys. Rev. Lett. 131, 176604 – Published 27 October 2023

Abstract

We perform a systematic study of Andreev conversion at the interface between a superconductor and graphene in the quantum Hall (QH) regime. We find that the probability of Andreev conversion from electrons to holes follows an unexpected but clear trend: the dependencies on temperature and magnetic field are nearly decoupled. We discuss these trends and the role of the superconducting vortices, whose normal cores could both absorb and dephase the individual electrons in a QH edge. Our Letter may pave the road to engineering a future generation of hybrid devices for exploiting superconductivity proximity in chiral channels.

Received 2 April 2023
Accepted 28 September 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.176604

Physics Subject Headings (PhySH)

Quantum Hall effect Topological superconductors

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Lingfei Zhao ^1,*, Zubair Iftikhar¹, Trevyn F. Q. Larson¹, Ethan G. Arnault ¹, Kenji Watanabe ², Takashi Taniguchi², François Amet³, and Gleb Finkelstein¹

¹Department of Physics, Duke University, Durham, North Carolina 27708, USA
²National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
³Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina 28607, USA

^*lz117@duke.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 131, Iss. 17 — 27 October 2023

Reuse & Permissions

Access Options

Article part of CHORUS

Accepted manuscript will be available starting 26 October 2024.

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Optical image (left) and 3D schematics (right) of the device. The black dashed lines label the boundaries of the graphite gate underneath. The yellow electrodes are normal $Cr / Au$ contacts and the light gray is the superconducting MoRe, which forms 0.5 and $1 μ m$ interfaces with graphene. (b) Sketch of the measurement setup. The current is injected from the upstream contact into the grounded superconductor, while measuring the voltage at the downstream contact. (c) The maximum and minimum values of $R_{d}$ (left) and $P_{e h}$ (right) measured for the shorter interface. The statistical information is collected in the $V_{G}$ range corresponding to $ν = 2$ , as outlined by the green lines in Fig. 3. The temperature is 40 mK.
Reuse & Permissions
Figure 2
(a) $P_{e h}$ measured for the $0.5 μ m$ interface as a function of $V_{G}$ on top of the $ν = 2$ plateau at $B = 2.2 T$ . The temperature is varied from the base temperature of 40 to about 670 mK. (b) The standard deviation of $P_{e h}$ of the $0.5 μ m$ (filled triangle) and $1 μ m$ (open circle) interfaces as a function of temperature at various magnetic fields. The inset plots the decay constant $T_{0}$ obtained from exponential fits vs the magnetic field. The lines represent the averages of the dots.
Reuse & Permissions
Figure 3
(a) $P_{e h}$ plotted against $B$ and $V_{G}$ for $L = 0.5 μ m$ (left) and $1 μ m$ (right) at $T = 40 mK$ . The green lines mark the region of the $ν = 2$ plateau used for the analysis in panel (b) and Fig. 1. (b) The standard deviation $σ$ of $P_{e h}$ measured over the $V_{G}$ range corresponding to $ν = 2$ . The top and bottom gray curves correspond to the $L = 0.5$ and $1 μ m$ interfaces. The lower curve saturates upon reaching the noise floor of the experiment, at $σ \approx 2.5 \times 10^{- 3}$ . The symbols (circles and triangles) represent $σ$ averaged over 100 mT range, ${⟨ σ ⟩}_{Δ B}$ . This averaging reveals the overall decay trend of $σ$ , represented by the exponential fits (straight solid and dashed lines).
Reuse & Permissions
Figure 4
(a) Histograms of $P_{e h}$ collected for the longer interface in the 1.4–1.5 T window on the $ν = 2$ plateau at various temperatures. (b) The same data as in (a) rescaled by fitting a phenomenological triangular shape (lines) and normalizing $x$ axis by the fitted width of the triangle. The curves are offset by 0.2 along the $y$ axis. Left inset: the same normalized distributions replotted without an offset. Right inset: the fitted width of the triangle plotted vs $T$ . The line is a guide for the eye, which follows the decay constant $T_{0}$ obtained in Fig. 2.
Reuse & Permissions

Physical Review Letters