Enhanced Macroscopic Quantum Tunneling in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ Intrinsic Josephson Junction Stacks

TL;DR

This study demonstrates a significant enhancement of macroscopic quantum tunneling in stacks of intrinsic Josephson junctions in Bi$_2$Sr$_2$CaCu$_2$O$_{8+eta}$, driven by current fluctuations and environmental impedance effects.

Contribution

It reveals that the quantum tunneling rate in junction stacks scales with the square of the number of junctions, a novel finding in the context of high-temperature superconductor devices.

Findings

Quantum tunneling rate scales as N^2 in junction stacks.

Current fluctuations and environmental impedance significantly boost tunneling.

Enhanced tunneling observed at millikelvin temperatures with microwave irradiation.

Abstract

We have investigated macroscopic quantum tunneling in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ intrinsic Josephson junctions at millikelvin temperatures using microwave irradiation. Measurements show that the escape rate for uniformly switching stacks of N junctions is about $N^2$ times higher than that of a single junction having the same plasma frequency. We argue that this gigantic enhancement of macroscopic quantum tunneling rate in stacks is boosted by current fluctuations which occur in the series array of junctions loaded by the impedance of the environment.