Numerical analysis of spin-orbit coupled one dimensional Fermi gas in the magnetic field

TL;DR

This study uses advanced numerical methods to analyze the phases of a spin-orbit coupled one-dimensional Fermi gas under magnetic fields, revealing multiple phases and the absence of Majorana fermions contrary to mean field predictions.

Contribution

It provides a detailed numerical investigation of the phase diagram and pairing mechanisms in a spin-orbit coupled Fermi gas, challenging previous mean field results regarding Majorana fermions.

Findings

Identification of multiple phases including PI, SC, LE, and BI.

Discovery of triplet pairing order induced by spin-orbit coupling.

No evidence of Majorana fermions in the studied system.

Abstract

We use the density matrix renormalization group method(DMRG) and the infinite time evolved block decimation method(iTEBD) to investigate the ground states of the spin-orbit coupled Fermi gas in a one dimensional optical lattice with a transverse magnetic field. We discover that the system with attractive interaction can have a polarized insulator(PI), a superconducting phase(SC), a Luther-Emery(LE) phase and a band insulator(BI) phase as we vary the chemical potential and the strength of magnetic field. We find that spin-orbit coupling induces a triplet pairing order at zero momentum with the same critical exponent as that of the singlet pairing one in both the SC and the LE phase. In contrast to the FFLO phase found in the spin imbalanced system without spin-orbit coupling, pairings at finite momentum in these two phases have a larger exponent hence do not dictate the long range behavior. We also find good agreements of the dominant correlations between numerical results and the prediction from the bosonization method. The presence of Majorana fermions is tested. However, unlike results from the mean field study, we do not find positive evidence of Majorana fermions in our system.