Research progress of infrared reflectance spectrum characteristics of lithium titanate superconductors in Chinese Academy of Sciences

【Chinese Instrument Network Instrument R&D】 Recently, the Xu Wen Group of the Institute of Solid State Physics, Chinese Academy of Sciences, Hefei Institute of Materials Science, in collaboration with Shandong University and the Institute of Physics of the Chinese Academy of Sciences, has made new progress in the infrared reflectance spectral characteristics of lithium titanate superconductors.

Near Infrared Reflectance Spectra of Lithium Titanate Superconducting Thin Films at Different Temperatures

By studying the infrared reflectance spectroscopy characteristics of different lattice orientations of lithium titanate superconductors, the metal-superconductivity transition and electronic localization effects of light detection were observed. The results were published in Optics Letters, 42(8), 1552- 1555 (2017)) Magazine.

Lithium titanate superconductor is a type of conventional superconducting material with a superconducting transition temperature of about 10K discovered in 1973. Lithium titanate superconductor as a superconducting thin film material has a wide application prospect in the fields of electric energy, superconducting magnets, communications and microelectronics, and its physical properties such as thermal, electrical, magnetic transport, scanning tunneling spectrum, etc. have been widely studied. Among them, electrical transport measurements have shown that the metal-superconducting transition temperature of lithium titanate superconducting thin film material is between 10-12K, and the superconducting thin films of [001] and [111] crystal orientation have anisotropy. However, no careful study of the optical characteristics of this superconductor has been conducted so far.

Based on this, researchers of Xu Wen's group collaborated with other units to prepare lithium titanate superconducting thin films ([001] and [111] orientations) on a magnesium aluminum oxide substrate by pulsed laser deposition in the near-infrared region. (1-2μm), For the lithium titanate superconducting thin film, the condition ωτ ~ 1 is satisfied (where ω is the infrared light frequency and τ is the relaxation time of electrons in the sample), so the near-infrared reflectance spectrum is a non-contact optical The measurement method can be directly applied to measure the infrared optical properties of a lithium titanate superconducting film. The results show that the metal-superconducting transition temperature of the light-sensing lithium titanate superconducting thin film is consistent with the measurement results of electrical transport; the superconducting transition temperature of lithium titanate with different lattice orientation ([001] and [111] orientation). At 9K and 11K, respectively, the resistance of the metal state measured by light measurement and electrical transport is consistent with the temperature; the electron localization effect is observed in the lithium titanate superconducting thin film in the metal state. This result is the conventional electrical and magnetic losses. The measurement cannot be directly observed.

This work utilizes simple optical measurements and eliminates the need to fabricate ohmic contact electrodes on the sample, and observes consistent results with electrical transport measurements and resistance localization effects that cannot be measured with conventional electrical transport measurements, providing for the study of superconducting materials. Simple measurement methods provide optical research experimental data for understanding the mechanism of superconductivity. One of the review experts of the article only commented on the review of the paper: The paper is very good.

The above research has been funded by the National Natural Science Foundation of China and the Science and Technology Department of the Foundation.

(Original Title: Research Progress of Infrared Reflectance Spectroscopy Properties of Lithium Titanate Superconductors)