2024/10/16 by Cajetan Heinz, Patrik Recher, Heinz, Cajetan +4 · 1 citation
Physics and Astronomy · #Atomic and Subatomic Physics Research #Condensed matter physics #Josephson effect #Magnetic field #Physics #Pi Josephson junction #Quantum #Quantum Hall effect #Quantum and electron transport phenomena #Quantum mechanics #Quantum optics and atomic interactions #Quantum spin Hall effect #Spin (aerodynamics) #Superconductivity
paper · pdf · doi:10.21468/scipostphyscore.9.3.042
openalex created_date 2024/10/20 · openalex publication_date 2026/07/21 · openalex updated_date 2026/08/05
Using standard tight-binding methods, we investigate a novel backscattering mechanism taking place on quantum spin Hall N’SNSN’ Josephson junctions in the presence of time-reversal symmetry. This extended geometry allows for the interplay between two types of Andreev bound states (ABS): the usual phase-dependent ABS localized at the edges of the central SNS junction and phase-independent ABS localized at the edges of the N’S regions. Crucially, the latter arise at discrete energies En <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msub> <mml:mi>E</mml:mi> <mml:mi>n</mml:mi> </mml:msub> </mml:math> and mediate a backscattering process between opposite edges on the SNS junction, yielding gap openings when both types of ABS are coherently coupled. In this scenario, a 4 π <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>π</mml:mi> </mml:math> -periodic ABS decouples from the rest of the 2 π <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>π</mml:mi> </mml:math> -periodic spectrum, yielding several observable consequences: Firstly, we show that the 4π <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>4</mml:mn> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> -periodic spectrum can be probed by means of the Shapiro experiment even in the presence of dynamical transitions between the ABS and the quasicontinuum. Secondly, the presence of this backscattering mechanism distorts the superconducting quantum interference (SQI) pattern within the length scale, determined by the ratio between 4π <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>4</mml:mn> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> - and 2π <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> -periodic supercurrent contributions. Finally, we propose to use a magnetic flux to tune En <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msub> <mml:mi>E</mml:mi> <mml:mi>n</mml:mi> </mml:msub> </mml:math> to zero, resulting in the selective lifting of the fractional Josephson effect.