Sponsor(s): Chinese Physical Society & Institute of Physics (CAS )
24 issues per year
Current Issue: Issue 05, 2020
Acta Physica Sinica is supervised by Chinese Academy of Sciences, sponsored by Chinese Society of Physics and Institute of Physics CAS. It aims to disseminate the achievements in the field of physics in China, promote academic exchanges and the study of physics, especially providing an important platform for young talents. Acta Physica Sinica is included in CA, EI, CSCD and AJ. Impact factor is 1.349.
Editor-in-Chief: OuYang Zhong-can
Acta Physica Sinica,2020,Vol 69,No. 05
In recent years, the research on topological materials, including topological insulator and topological semimetal, has received a lot of attention in condensed matter physics. HgCdTe, widely used in infrared detection, also holds huge potential in this field. It has been reported that the strained thin Hg 0.865Cd 0.135Te can realize the topological insulator phase by using a CdZnTe substrate. However, the stress caused by changing the substrate has great limitations. For example, the stress cannot be changed once the sample has been grown. Hence, we tried to use piezoceramics (PZT) instead to implement the stress and control the properties of HgCdTe. The main purpose of our experiment was to verify its validity. As is well known, the band structure of Hg 1– xCd xTe can be precisely controlled by changing the content of Cd. When x lies between 0 and 0.165, HgCdTe features an inverted band structure, which is the premise of realizing the topological phase. In this work, an inversion layer was induced on a single crystal grown HgCdTe bulk material by anodic oxidation, whose content of Cd was confirmed to be 0.149 by using XRD. Then the sample was thinned and attached to PZT, and the tuning of stress was realized by applying a voltage to the sample. Ohmic contacts were realized by indium in van der Pauw configuration. All measurements were carried out by using an Oxford Instruments 4He cryostat with a magnetic field applied perpendicularly to the sample plane. At 1.5 K and zero voltage, an evident SdH oscillation was observed. By fitting the linear relationship between the filling factor and the reciprocal of the magnetic field, we obtained the concentration as ns = 1.25 × 10 16 m −2. Subsequently, we scanned the voltage from 200 V to −200 V continuously in different magnetic fields. Two phenomena with different characteristics were observed. It is found that the resistance changes linearly with the stress at zero fields, while an SdH oscillation-like behavior occurs at high fields. We attribute such a difference to the existence of two conductive channels: One is the bulk material and the other is the two-dimensional electron gas. It is also noteworthy that the topological phase in our sample cannot be determined because the quantum Hall conductance is polluted by the conductance of the bulk material. In conclusion, our results show that it is an effective way to use the PZT to tune the stress and this method can also be applied to the research of other materials.