Role of dissipation in realistic Majorana nanowires

We carry out a realistic simulation of Majorana nanowires in order to understand the latest high-quality experimental data [H. Zhang et al., arXiv:1603.04069 (2016)] and, in the process, develop a comprehensive picture for what physical mechanisms may be operational in realistic nanowires leading to discrepancies between minimal theory and experimental observations (e.g., weakness and broadening of the zero-bias peak and breaking of particle-hole symmetry). Our focus is on understanding specific intriguing features in the data, and our goal is to establish matters of principle controlling the physics of the best possible nanowires available in current experiments. We identify dissipation, finite temperature, multi-sub-band effects, and the finite tunnel barrier as the four most important physical mechanisms controlling the zero-bias conductance peak. Our theoretical results including these realistic effects agree well with the best available experimental data in ballistic nanowires.

Figure 1

(a) Best-fitting conductance. Gate voltage in the lead is assumed to give $E_{\mathrm{lead}}=-20\text{meV}$. The narrow barrier has width $D=20\text{nm}$ and height $E_{\mathrm{barrier}}=30\text{meV}$. (b) Line cuts from the data in (a) with vertical offsets $0.02\times 2e^2/h$. The inset zooms into the region close to the topological phase transition with vertical offsets $0.01\times 2e^2/h$.

Figure 2

Tunneling conductance at different temperatures without dissipation. Finite temperature broadens the ZBCP and lowers its peak value simultaneously, without breaking any p-h symmetry. Chemical potential of the first band is ${\mu }_1=0\text{meV}$. Only (a) is calculated by kwant; others are generated by convolution.

Figure 3

Tunneling conductance with various dissipation at zero temperature. Dissipation lowers the peak value of ZBCP and broadens its width. Furthermore, it breaks p-h symmetry in conductance at finite energies. Chemical potential of the first band is ${\mu }_1=0\text{meV}$. All the four plots are generated by kwant.

Figure 4

The peak value and FWHM of ZBCP for temperature and dissipation. Data points on the red curve are obtained at increasing temperature but without dissipation, while points on the blue curve are obtained with increasing dissipation at $T=0$. $V_z=2\text{meV},{\mu }_1=0\text{meV}$.