Physics researchers identify new multiple Majorana zero modes in superconducting SnTe

A collaborative research team has identified the world’s first multiple Majorana zero modes (MZMs) in a single vortex of the superconducting topological crystalline insulator SnTe and exploited the crystal symmetry to control the coupling between the MZMs.

This discovery, published in Natureoffers a new path to realizing fault-tolerant quantum computers. The team was led by Professor Junwei Liu, Associate Professor in the Department of Physics at the Hong Kong University of Science and Technology (HKUST), and Professors Jinfeng Jia and Yaoyi Li from Shanghai Jiao Tong University (SJTU).

The MZM is a topologically nontrivial zero-energy quasiparticle in a superconductor that obeys non-Abelian statistics, which allows for inequivalent braiding sequences, even if the total number of exchanges is the same. This contrasts with ordinary particles, such as electrons or photons, where different braiding always results in the same final state. This unique property protects MZMs from local perturbations, making them an ideal platform for robust and fault-tolerant quantum computing.

Although significant progress has been made in the engineering of artificial topological superconductors, braiding and manipulating MZMs remains extremely challenging due to their separation in real space, which complicates the movements required for hybridization.

The recently published work, carried out in collaboration by the theoretical group at HKUST and the experimental group at SJTU, took a completely different approach by taking advantage of the unique feature of crystal symmetry-protected MZMs to eliminate these bottlenecks.

They demonstrated for the first time the existence and hybridization of multiple magnetic mirror-shielded MZMs in a single vortex of the superconducting topological crystalline insulator SnTe, using controlled methods that do not require real spatial motion or strong magnetic fields, leveraging their extensive experience in low-temperature scanning tunneling microscopy, high-quality sample growth, and large-scale theoretical simulations.

The SJTU experimental group observed significant changes in the zero-polarization peak, a strong indicator of MZMs, in the SnTe/Pb heterostructure under tilted magnetic fields. The HKUST theoretical team then performed extensive numerical simulations to demonstrate unambiguously that the anisotropic responses to tilted magnetic fields indeed originate from MZMs protected by crystal symmetry.

Using the polynomial kernel method, they successfully simulated large vortex systems with hundreds of millions of orbitals, which allowed further exploration of new properties of vortex systems beyond just crystal symmetry-protected MZMs. The research opens a new frontier for the detection and manipulation of multiple crystal symmetry-protected MZMs.

Their findings pave the way for the experimental demonstration of non-Abelian statistics and the construction of new types of topological qubits and quantum gates based on multiple MZMs protected by crystal symmetry.