서강대학교

초록

Dirac material attracted a lot of interests due to the linear band dispersion. Recently, three-dimensional Dirac and Weyl semimetals has invoked intriguing phenomena originating from the non-trivial Berry phase. Many interesting electrical transport phenomena were studied and reported. However, magnetic properties which is associated with the non-trivial Berry phase has been rarely reported. In this study, we prepared ZrTe5 single crystal which is known as Dirac semimetal with highly anisotropic Fermi surface. We also prepared doped crystals, TixZr1-xTe5, and compared. The detailed electrical transport measurements revealed that the crystals show the Lifshitz transition, and the Ti doping induces a Fermi level shift. Further quantum oscillation analyses demonstrate that the TixZr1-xTe5 crystals are 3D Dirac semimetals. Importantly, we observed that the magnetic susceptibility is strongly temperature-dependent and has a minimum value. Interestingly, the hallmark of ZrTe5 is that the resistivity shows a maximum at a certain temperature. It turned out that the minimum susceptibility and the maximum resistivity happen at the same temperature. This observation is interpreted in terms of the Berry paramagnetism which is distinct property of Dirac semimetal. We further studied ZrTe5-xSbx. Sb doping can induce large carrier doping. Electrical measurements showed that Sb-doped ZrTe5 crystal is p-type while undoped ZrTe5 is n-type. In addition, the resistivity of p-type ZrTe5 showed much different behavior from undoped ZrTe5. The resistivity does not decrease as much as that of the undoped crystal at low temperature. This behavior was already calculated theoretically, but no experimental results were reported. The agreement between our result and the theory implies that the susceptibility anomaly can be observed in other Dirac semimetals and topological materials. This study paves the way to determine topology and characters of the bands.