Date and Time: 18-July-2024（Thursday）3:00pm (Beijing time)

Venue: Room 526

Speaker:Jinxin Hu, Nanyang Technological University, Singapore

Host: Chuanchang Zeng ( BAQIS)

Title: Theory of supercurrent in chiral Josephson junctions

About the Speaker:

Jinxin Hu graduated from the Hong Kong University of Science and Technology in 2023, and then worked as a post-doctoral at Nanyang Technological University in Singapore. His main works on theoretical condensed matter physics including the topics:

1.Quantum transport theory, such as nonlinear Hall effect and nonlinear optics.

2.Unconventional superconductivity, including theoretical directions such as two-dimensional superconductors and topological superconductivity, as well as specific materials such as transition metal dichalcogenides and Moiré superlattice.

3.Quantum geometry effects in superconductors.

4.Fractional Chern insulator based on Moiré superlattice.

Abstract:

Recently, several experiments reported that the magnetic field interference pattern of the quantum hall edge states mediated Josephson junctions can exhibit Fraunhofer oscillations with a periodicity of either h/e or h/2e. However, a unified understanding of such a phenomenon is still absent. In this talk, I will discuss the competition between crossed Andreev reflections and local Andreev reflections results in the crossover between h/e and h/2e quantum oscillations in chiral edge-channel Josephson junctions. Our theory explains why recent experiments observed either h/e or h/2e oscillations in different samples. Furthermore, we explain that when the chiral Andreev edge state couple, a pair of localized Majorana modes appear at the ends of the Josephson junction, which are robust and independent of the phase difference between the two superconductors. As the h/2e-periodicity and the Majorana zero modes have the same physical origin, the Fraunhofer oscillation period can be used to identify the regime with Majorana zero modes.

[1] Jin-Xin Hu, et al. "Josephson diode effect induced by valley polarization in twisted bilayer graphene." Phys. Rev. Letters 130.26 (2023): 266003.

[2] Zi-Ting Sun, Jin-Xin Hu*, et al. " Anomalous h/2e-periodicity and Majorana zero modes in chiral Josephson 、junctions." Phys. Rev. Letters (in press).