Excess equilibrium noise in a topological SNS junction between chiral Majorana liquids

Abstract

We consider a Josephson contact mediated by 1D chiral modes on a surface of a 3D topological insulator with superimposed superconducting and magnetic layers. The system represents an interferometer in which 1D chiral Majorana modes on the boundaries of superconducting electrodes are linked by ballistic chiral Dirac channels. We investigate the noise of the Josephson current as a function of the dc phase bias and the Aharonov-Bohm flux. Starting from the scattering formalism, a Majorana representation of the Keldysh generating action for cumulants of the transmitted charge is found. At temperatures higher than the Thouless energy E Th , we obtain the usual Johnson-Nyquist noise, 4G0kBT , characteristic for a single-channel wire with G0 ≡ e 2 /(2π ). At lower temperatures the behavior is much richer. In particular, the equilibrium noise is strongly enhanced to a temperature-independent value ∼ G0E Th if the Aharonov-Bohm and superconducting phases are both close to 2πn, which are points of emergent degeneracy in the ground state of the junction. The equilibrium noise is related to the Josephson junction's impedance via the fluctuation-dissipation theorem. In a striking contrast to usual Josephson junctions (tunnel junctions between two s-wave superconductors), the real part of the impedance does not vanish, reflecting the gapless character of Majorana modes in the leads.

Locking of magnetization and Josephson oscillations at ferromagnetic resonance in $φ_0$ junction under external radiation

“…The ϕ 0 -junction related to a special class of anomalous Josephson structures with coupled superconducting and magnetic characteristics allows to manipulate the magnetic properties by Josephson current [1][2][3][4][5][6]. It demonstrates a number of interesting features important for superconducting spintronics and modern informational technologies [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The current-phase relation of the ϕ 0 -junction is given by I = I c sin(ϕ − ϕ 0 ), where the phase shift ϕ 0 is proportional to the magnetic moment perpendicular to the gradient of the asymmetric spin-orbit potential [23,24].…”

Microwave response of a chiral Majorana interferometer

“…Interferometers based on chiral Majorana modes should allow probing the nontrivial physics of these systems [14][15][16][17][18][19][20][21][22][23][24]. The first proposals addressed the dctransport [14,15].…”