Anomalous Magneto-Transport Behavior in Transition Metal Pentatelluride HfTe ₅

Abstract

There is a long-standing confusion concerning the physical origin of the anomalous resistivity peak in transition metal pentatelluride HfTe5. Several mechanisms, such as the formation of charge density wave or polaron, have been proposed, but so far no conclusive evidence has been presented. In this work, we investigate the unusual temperature dependence of magneto-transport properties in HfTe5. It is found that a three-dimensional topological Dirac semimetal state emerges only at around Tp (at which the resistivity shows a pronounced peak), as manifested by a large negative magnetoresistance. This accidental Dirac semimetal state mediates the topological quantum phase transition between the two distinct weak and strong topological insulator phases in HfTe5. Our work not only provides the first evidence of a temperature-induced critical topological phase transition in HfTe5 but also gives a reasonable explanation on the long-lasting question.

Large magnetothermopower and anomalous Nernst effect in HfTe5

“…The total conductivity extracted from the resistance measurements shown in Fig. S3 around T p at zero magnetic field is σ = σ − 0 + σ + 0 = 333 −1 cm −1 , which is fairly close to the value given by Zhao et al [20]. As there are six parameters to adjust, it is not surprising to account for the data using reasonable values for every one of them, but we noticed that this empirical two-band model fails to reproduce the concavity of the experimental data in the lowest field range, no matter how we try to set the fitting parameters.…”

“…The anomalous resistivity peak [ Fig. S3(a)] is another indication that, around the transition temperature, both EL and HL carriers contribute [20]. Therefore, a twoband model needs to be considered once again to account for the longitudinal MTEP near T p .…”

“…Figure 1(b) shows the corresponding 3D Brillouin zone (BZ) [15]. A peak anomaly of the electric resistivity in the temperature range from 40 K to 80 K has been observed by different groups [16][17][18][19][20]. The seminal work by Jones et al [18] showed that the Seebeck coefficient changes sign at about 85 K, which they interpreted as a change of charge carrier type, from electronlike (EL) to holelike (HL).…”

Unconventional Hall response in the quantum limit of HfTe5

“…Upon cooling in zero magnetic field, ρ xx increases with decreasing T until it reaches a maximum at T L = 70 K ( Fig.1a). Such a maximum has previously been observed in HfTe 5 32 and ZrTe 5 21 , and it is attributed to a Lifshitz transition, here inducing a change in charge-carrier type. Consistently, the slope of ρ xy (B) changes sign at T L , indicating electron-type transport for T < T L 32 .…”

Log-periodic quantum magneto-oscillations and discrete-scale invariance in topological material HfTe5

“…Lately, the electrical transport measurements have revealed that HfTe 5 shows ultrahigh mobility [23], indicating great promise in electronic applications. In addition, the negative MR under parallel magnetic and electrical fields is observed in HfTe 5 [23,24], which could be attributed to the chiral anomaly [25,26] or the nontrivial Berry curvature [27,28]. The pressure induced superconductivity in HfTe 5 also illustrates interesting property of the system [29,30].…”