Recently, Prof. TIAN Mingliang's team from High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL) reported the observation of large linear magnetoresistance (LMR) in a bismuth nanoribbon.

Bismuth is an old Dirac material with fascinating quantum effects due to unusual electronic properties such as low carrier density, small effective mass and long mean free path.

In early studies, very large LMR in Bi has been observed in thick films, lines patterned from the Bi films, and polycrystalline nanowires.

However, the thickness of the films or lines in these studies is in the range of micrometers. It is known that when the sample size is comparable with the electron Fermi wavelength, the quantum size confinement effect would lead to exotic new behaviors that are differ from the bulk samples.

Thus, it is interesting to know whether the LMR can be observed when the thickness of the films is turned into nanometer scale, especially in the confined geometries with an enhanced surface conductivity, e.g. nanowires or nanoribbons.

To address this question, the researchers investigated the MR in Bi by using Bi nanoribbons.

They fabricated high quality Bi single-crystalline nanoribbons with thickness ranging from 100 ~ 30 nm, which is orders of magnitude smaller than the samples used in previously studies, and provides a good platform to study the LMR in Bi with confined geometries.

From transport measurements on an individual nanoribbon with thickness about ~ 100 nm, large LMR that with non-monotonical temperature dependence was observed, which shows a broad peak at ~125 K with MR reaching 550%.

Furthermore, the LMR persists up to room temperature with considerable MR ratio ~ 200%. From data analyses, they found that the LMR in Bi nanoribbons can be understood with the quantum-MR model.

The observation of large LMR in Bi nanoribbons at room temperature makes nanoscale potentially applicable in practice.

The results have been published in Appl. Phys. Lett. with the title of "Large linear magnetoresistance in a bismuth nanoribbon".

This work was supported by the Natural Science Foundation of China, and the National Key Research and Development Program of China, the program of Users with Excellence, the Hefei Science Center of CAS, the CAS/SAFEA international partnership program for creative research teams of China.

The temperature-dependence of resistance of a Bi nanoribbon with thickness ~100 nm under magnetic field B = 0 and 16 T. Inset: a SEM image of a nanoribbon device with four probes. (Imaged by NING Wei)