1

Pressure-induced superconductivity in ZrTe5

Yonghui Zhou1, Wei Ning2, Yongping Du3, Zhenhua Chi1,2, Xuliang Chen1,2, Xuefei

Wang1, Xiangde Zhu2, Xiangang Wan3,4, Zhaorong Yang1,2,4†, Mingliang Tian2,4† &

Yuheng Zhang2,4

1 Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese

Academy of Sciences, Hefei, Anhui, 230031, China.

2 High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031,

China.

3 National Laboratory of Solid State Microstructures, College of Physics, Nanjing

University, Nanjing, 210093, China.

4 Collaborative Innovation Center of Advanced Microstructures, Nanjing University,

Nanjing, 210093, China.

†Correspondence and requests for materials should be addressed to Z.Y. (e-mail:

zryang@issp.ac.cn); or to M.T. (e-mail: tianml@hmfl.ac.cn)

2

As a new topological material, ZrTe5 exhibits novel properties. Pressure is

believed to be effective for studying the topological phase transitions

experimentally. In this work, we have performed resistance and ac magnetic

susceptibility measurements for ZrTe5 single crystal at various pressures up to

68.5 GPa. We show that, accompanied by complete suppression of the high

temperature resistance anomaly, superconductivity is induced at a critical

pressure of 6.2 GPa. The superconducting transition temperature Tc initially

increases with pressure then decreases slightly with a maximum of 4.0 K at 14.6

GPa. At pressures above 21.2 GPa, a second superconducting phase with the

maximum Tc of about 6.0 K manifests and coexists with the original one. We also

performed the density functional theory calculations to explore the possibility of

topological superconductivity in the pressurized ZrTe5.

3

Dirac materials including topological insulators (TIs)1-3, Dirac semimetals4,5 and

Weyl semimetals5-7 belong to a new type of quantum matter and attract extensive

attention in the past few years. ZrTe5 is a layered material with orthorhombic crystal

structure and has been known for a long time due to its large thermoelectric power8,9,

resistivity anomaly10,11 and a large positive magnetoresistance12. However, recent

theoretical work13,14 has proposed that single-layer ZrTe5 is a large gap Quantum spin

Hall (QSH) insulator, while the bulk ZrTe5 formed by the stacking of layers are located

in the vicinity of a transition between strong and weak topological insulator. These

interesting new predictions spark the renewed interests in the research of its Dirac and

topological characters. Indeed, the magneto-transport experiments have observed the

chiral magnetic effect and the angle-resolved photoemission spectroscopy (ARPES)15

provided that the electronic structure of ZrTe5 is consistent with that of the 3D Dirac

semimetals which is similar to that in Na3Bi16-18 and Cd3As219-23. These results suggest

that ZrTe5 is a very promising system that host topological properties and might help to

pave a new way for further experimental studies of topological phase transitions.

To investigate these new quantum states, pressure is used as an important control

parameter to tune the quantum phases of the system24-26. It was well known that pressure

can effectively tune lattice structures and the corresponding electronic states in a more

systematic fashion, which avoids the complexity brought by chemical doping. In this

work, by performing resistance and ac magnetic susceptibility measurements for ZrTe5

single crystal at various pressures up to 68.5 GPa, we report the observation of pressure-

induced semimetal to metal and superconducting transition at a critical pressure of 6.2

GPa. It was found that the occurrence of the metallic phase/or superconductivity at 6.2

GPa is always accompanied by the complete suppression of the big resistance peak near

128 K by the pressure. It seems that two superconducting phases were obtained, one

4

shows a sharp resistance drop with a zero resistance near 3.8 K which is robust at

pressures up to 68.5 GPa. The second one that presents a broad resistance drop but with

a finite resistance starting from 6.0 K is visible only at a pressure above 21.2 GPa.

ZrTe5 single crystals were grown via iodine vapor transport method in a two-zone

furnace with elements Zr (99.99%) and Te (99.99%)27. The crystals show a thin

elongated rectangular shape, where the prismatic ZrTe6 chains run along the

crystallographic a-axis and linked along the c-axis via zigzag chains of Te atoms to

form two-dimensional (2D) layers, stacked along the b-axis into a crystal28. Structural

and compositional characterizations of the crystals by X-ray diffraction, scanning (or

transmission) electron microscopy, together with electron diffraction and energy

dispersive X-ray spectroscopy (EDS) studies confirm its high quality. High pressures

were generated with a screw-pressure-type diamond anvil cell (DAC) made of non-

magnetic Cu-Be alloy. Single crystals with typical dimension of 100×30×10 μm3 were

loaded without pressure-transmitting medium for run 1, while for run 2 loaded with

Daphne 7373 oil as pressure-transmitting medium. The easily cleaved crystal was

pressurized along b-axis and the standard four-probe resistance measurement was

performed along the c-axis, as illustrated schematically in the inset of Fig. 1(a). The

high-pressure ac susceptibility was measured using magnetic inductance technique.

The diamond culet was 800 μm in size and a Be-Cu gasket was pre-indented from 450

μm to 200 μm. Pressure was calibrated by using the ruby fluorescence shift at room

temperature for all experiments29. The electronic band structure calculations have been

carried out by using the full potential linearized augmented plane wave method as

implemented in WIEN2K package30. Local-density approximation (LDA) has been

adopted as the exchange-correlation potential. 24×24×6 and 30×30×8 k-mesh are used

to sample the Brillouin zone for self-consistent calculation and Fermi surface,

5

respectively. Spin-orbit coupling for all elements was taken into account by a second-

variational method.

Figure 1(a) and 1(c) shows the evolution of the resistance as a function of

temperature for ZrTe5 single crystal at various pressures. Upon cooling at 0.5 GPa from

300 K down to 1.8 K, the overall behavior of resistance displays a typical

semiconducting-like feature above 128 K, then decreases with the decrease of

temperature followed by a slight upturn below 20 K. The large resistance anomaly

around 128 K is quite similar to those observed under ambient pressure12,15,31 and was

generally correlated to the sign change of charge carriers although the origin still

remains elusive31. With increasing pressure, the peak temperature increases initially up

to 150 K and then shifts back towards lower temperatures accompanied by the

broadening of the peak and the decrease of the peak resistance. Since it was reported

that the resistance anomaly could be strongly enhanced by an application of magnetic

field, we investigated the magnetoresistance (MR) at the peak temperature for different

pressures. As shown in Fig. 1(b), the magnetotransport properties at each pressure show

positive MR behavior with the increase of magnetic field but the magnitude of the MR

decreases monotonically with the increase of pressure no matter where the peak

temperature locates.

Surprisingly, with further increasing pressure, accompanied by complete

suppression of the resistance anomaly peak, a metallic transport behavior with an

almost constant normal state resistance within 5% is obtained and a small drop of

resistance is observed at ~2.5 K and 6.2 GPa. At 6.7 GPa, the resistance drops to zero

at 1.8 K, signaling the appearance of superconductivity (Fig. 1(c)). To make sure that

the drop of the resistance was indeed a superconducting transition, we carried out ac

magnetic susceptibility measurements on ZrTe5 at several pressures up to 9.0 GPa. As

6

seen from Fig. 1(d), diamagnetic signal is observed at 7.6 GPa and 9.0 GPa, which is

in agreement with the resistance measurements.

Figure 2(a) and 2(b) are the blow-up of the R-T curves at different pressures near

the superconducting transition, it was clearly seen that the superconducting transition

is quite sharp between 8.3 GPa and 21.2 GPa, indicating the bulk superconductivity.

However, when the pressure is applied up to 30.0 GPa, the onset temperature of the

resistance drop occurs from ~6.0 K, accompanied by a gradual decrease of resistance

down to 3.9 K, at which the sharp superconducting transition presents, as shown in Fig.

2(b). In fact, such a two-step like transition can be recognized from 25.3 GPa, implying

two superconducting phases coexist in the sample. With further increasing pressure, the

higher superconducting phase (SC-II) is suppressed gradually and the lower

superconducting transition (SC-I) becomes more and more sharp. Clearly, the SC-I

exists in a broad pressure region from 6.2 GPa to 68.5 GPa, the maximum pressure we

achieved in this work, while the SC-II manifests only at pressures above 21.2 GPa. It is

interesting to note that similar two-step like transition behavior has also been reported

in putative topological superconductor LuPdBi32.

Figure 3 displays temperature dependence of resistance under external magnetic

field aligned along b-axis of ZrTe5 at 14.6 GPa and 30.0 GPa, respectively. For both

cases, a finite resistive tail at low temperatures were clearly seen and gradually lifted

with the increase of magnetic field. A magnetic field of 1.5 T almost smears out the

superconducting transition completely. By defining Tc with two different resistance

criteria, we constructed the magnetic field (H) - temperature (T) phase diagrams, as

shown in Fig. 3(b) and 3(d). For P = 14.6 GPa, Tc decreases monotonically with

increasing magnetic field. The upper critical field μ0Hc2(0) is estimated to be about 1.54

T for the resistance criterion of Rcri = 90%Rn (Rn is the normal state resistance) and 1.26

7

T for the resistance criterion of Rcri = 50%Rn according to the Werthamer-Helfand-

Hohenberg (WHH) formula33. However, for P = 30.0 GPa, being associated with the

coexistence of SC-I and SC-II, the H-T phase diagram for the resistance criterion of Rcri

= 90%Rn is clearly divided into two parts. The Tc is depressed more pronounced at fields

below 0.2 T, which indicates that the SC-II is sensitive to the magnetic field. At fields

above 0.2 T, the superconductivity is dominated by the SC-I, where the R-T curves are

similar to those measured at 14.6 GPa. The Tc-H relationship can be described with the

WHH equation both at fields below and above 0.2 T, which gives μ0Hc2(0) about 0.46

T for SC-II and 1.26 T for SC-I. The large difference of μ0Hc2(0) indicates that the SC-

I and SC-II might have different origins.

It is noted that in both resistance and magnetic susceptibility measurements, we did

not use pressure-transmitting medium. To examine if the pressure induced

superconductivity is only related to the b-axis compression, a comparative experiment

of resistance measurement by using Daphne 7373 oil as the pressure-transmitting

medium was also carried out with pressure up to 20.3 GPa. In this run, a trace of

superconductivity was first observed at 7.2 GPa and a zero resistance was achieved at

10.8 GPa. All the characteristic temperatures in the above experimental results are

summarized in a T-P phase diagram shown in Fig. 4. It can be seen that, with increasing

pressure, the peak temperature of the resistance anomaly initially increases up to 150 K

and then decreases abruptly. When the peak anomaly disappears at the critical pressure

of 6.2 GPa, superconducting phase emerges immediately, indicating a possible quantum

critical point (QCP) near 6.2 GPa, below which the sample is semimetallic with a weak

topological character. However, if we carefully check the normal state resistance at 300

K and 10 K (see the inset of Fig. 4), both pressure-induced variations of normal state

resistance intuitively follows the T-P phase diagram. The slight enhancement of the

8

normal state resistance by the application of pressure up to 2.0 GPa is probably an

indication of the pressure-induced competition of the multiband carriers of the sample.

With further increasing pressure above 6.2 GPa, Tc increases monotonically until it

reaches a maximum of about 4.0 K at 14.6 GPa for the SC-I. The SC-II emerges only

above 21.2 GPa with the highest Tc of about 6.0 K. It sounds very clear that the pressure-

induced SC-I is a bulk superconductor, while the SC-II without zero resistance is not.

There are a number of possibilities that may be responsible for this tiny resistance drop

near 6.0 K. One of them is from the impurity phase in the sample. Because the resistance

drop reaches about 20%Rn, such a speculation is almost unlikely in our single crystal

sample. The second possibility is due to the pressure-induced fluctuation of

superconductivity, which is closely related to the SC-I. This suggestion cannot interpret

the linear-like decay of the resistance over a large temperature range of ~2 K and only

appears at a pressure larger than 21.2 GPa. A possible origin is that it is an independent

superconducting phase induced by the pressure but this phase is not a bulk phase, such

as the filamentary superconductivity which might be related to the edges/or surfaces of

the crystal34.

To have a comprehensive understanding of the physical properties of ZrTe5, we also

perform the density functional theory calculations for the electronic band structures.

Our result agrees well with the previous study, and confirms that this compound is a

weak topological insulator at ambient pressure13. We also perform calculations to

investigate the effect of high pressure. The total energies are calculated for a number of

different volumes ranging from 0.9V0 to 1.2V0, where V0 is the equilibrium unit-cell.

For each volume, the relaxations of cell geometry and atomic positions are carried out

using a conjugate gradient algorithm until the Hellman-Feynman force on each of the

unconstrained atoms is less than 0.001 eV/Å. The obtained volume versus the total

9

energy was found to be in good agreement with the Murnaghan equation of state35. Our

numerical bulk modulus at equilibrium is about 67.7 GPa, slightly larger than that of

WTe236 and MoS2

37.

Our calculations show that the pressure will change the band structure dramatically,

and at around 5.0 GPa, this compound becomes a metal. As shown in Fig. 5, at 7.0 GPa,

considerable states appear at the Fermi level, which agrees with the emergence of the

superconductivity at 6.2 GPa. As shown in Fig. 5(a), at 7.0 GPa there are two bands

cross the Fermi energy, forming a electron-like pocket and hole-like pocket around Γ

and Z point, respectively. The electron pockets denoted by the green color in Fig. 5(c)

are small and exhibit three-dimension character. While the hole pockets, i.e., red sheets

in Fig. 5(c), are much larger and display strong two-dimension feature. A time-reversal-

invariant topological insulator requires odd-parity symmetry and the Fermi surface

enclosing an odd number of time-reversal-invariant momenta (TRIM)38. The states at

Fermi surface are contributed to Zr-4d and Te-5p. Since these bands are spatially

extended, the electronic correlation should quite small due to the strong screening effect.

Consequently, one can expect that the superconductivity discovered in this work is

mediated by the electron-phonon interaction. Although the intra-pocket phonon

mediated pairing, which may has singular behaviour of the electron–phonon interaction

at long wavelengths, can possess odd-parity symmetry39. Unfortunately as shown in Fig.

5(c), the Fermi surface does not enclose any TRIM. Thus, this compound is unlikely

the topological superconductor at least at low-pressure region (less than 10.0 GPa). We

also perform band structure calculations for high-pressure region. As one expects that

increasing the pressure will increase the band width, consequently, there are many

bands cross the Fermi level and the Fermi surface becomes quite complicated as shown

in Fig. 5(b) and Fig. 5(d), and the possibility of topological superconductor at high

10

pressure cannot be exclude, which remains an open question.

In conclusions, by combining experimental and theoretical investigations, we

demonstrated the pressure-induced superconductivity on a weak topological insulator

ZrTe5. The appearance of superconductivity at the critical pressure is accompanied by

the complete suppression of the high temperature resistance anomaly around 128 K.

While our theoretical study rules out the possibility of topological superconductivity at

low pressure, at high pressure (above 20.0 GPa) the system has complicate Fermi

surface and a possible second superconducting phase, thus deserving further study.

11

References

1. Fu, L., Kane, C. L. & Mele, E. J. Topological Insulators in Three Dimensions. Phys. Rev. Lett. 98,

106803, (2007).

2. Hasan, M. Z. & Kane, C. L. Topological insulators. Rev. Mod. Phys. 82, 3045-3067, (2010).

3. Qi, X.-L. & Zhang, S.-C. Topological insulators and superconductors. Rev. Mod. Phys. 83, 1057-

1110, (2011).

4. Young, S. M. et al. Dirac Semimetal in Three Dimensions. Phys. Rev. Lett. 108, 140405, (2012).

5. Wan, X., Turner, A. M., Vishwanath, A. & Savrasov, S. Y. Topological semimetal and Fermi-arc

surface states in the electronic structure of pyrochlore iridates. Phys. Rev. B 83, 205101, (2011).

6. Wan, X., Vishwanath, A. & Savrasov, S. Y. Computational Design of Axion Insulators Based on 5d

Spinel Compounds. Phys. Rev. Lett. 108, 146601, (2012).

7. Burkov, A. A. & Balents, L. Weyl Semimetal in a Topological Insulator Multilayer. Phys. Rev. Lett.

107, 127205, (2011).

8. Jones, T. E., Fuller, W. W., Wieting, T. J. & Levy, F. Thermoelectric power of HfTe5 and ZrTe5. Solid

State Commun. 42, 793-798, (1982).

9. Lowhorn, N. D., Tritt, T. M., Abbott, E. E. & Kolis, J. W. Enhancement of the power factor of the

transition metal pentatelluride HfTe5 by rare-earth doping. Appl. Phys. Lett. 88, 022101, (2006).

10. Okada, S., Sambongi, T. & Ido, M. Giant Resistivity Anomaly in ZrTe5. J. Phys. Soc. Jpn. 49, 839-

840, (1980).

11. Skelton, E. F. et al. Giant resistivity and X-ray diffraction anomalies in low-dimensional ZrTe5 and

HfTe5. Solid State Commun. 42, 1-3, (1982).

12. Tritt, T. M. et al. Large enhancement of the resistive anomaly in the pentatelluride materials HfTe5

and ZrTe5 with applied magnetic field. Phys. Rev. B 60, 7816-7819, (1999).

13. Weng, H., Dai, X. & Fang, Z. Transition-Metal Pentatelluride ZrTe5 and HfTe5: A Paradigm for

Large-Gap Quantum Spin Hall Insulators. Phys. Rev. X 4, 011002, (2014).

14. Behrends, J., Grushin, A. G., Ojanen, T. & Bardarson, J. H. Visualizing the chiral anomaly in Dirac

and Weyl semimetals with photoemission spectroscopy. Preprint at http://arXiv.org/abs/1503.04329

(2015).

15. Li, Q. et al. Observation of the chiral magnetic effect in ZrTe5. Preprint at http://arXiv.org/abs/

1412.6543 (2014).

16. Xu, S.-Y. et al. Observation of a bulk 3D Dirac multiplet, Lifshitz transition, and nestled spin states

in Na3Bi. Preprint at http://arXiv.org/abs/1312.7624 (2013).

17. Liu, Z. K. et al. Discovery of a Three-Dimensional Topological Dirac Semimetal, Na3Bi. Science

343, 864-867, (2014).

18. Xu, S.-Y. et al. Observation of Fermi arc surface states in a topological metal. Science 347, 294-298,

(2015).

19. Neupane, M. et al. Observation of a three-dimensional topological Dirac semimetal phase in high-

mobility Cd3As2. Nat. Commun. 5, 3786, (2014).

20. Borisenko, S. et al. Experimental Realization of a Three-Dimensional Dirac Semimetal. Phys. Rev.

Lett. 113, 027603, (2014).

21. Liu, Z. K. et al. A stable three-dimensional topological Dirac semimetal Cd3As2. Nat. Mater. 13, 677-

681, (2014).

22. Liang, T. et al. Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd3As2. Nat.

Mater. 14, 280-284, (2015).

23. He, L. P. et al. Quantum Transport Evidence for the Three-Dimensional Dirac Semimetal Phase in

Cd3As2. Phys. Rev. Lett. 113, 246402, (2014).

24. Zhang, J. L. et al. Pressure-induced superconductivity in topological parent compound Bi2Te3. Proc.

Natl. Acad. Sci. USA 108, 24-28, (2011).

25. Zhang, C. et al. Phase diagram of a pressure-induced superconducting state and its relation to the

Hall coefficient of Bi2Te3 single crystals. Phys. Rev. B 83, 140504(R), (2011).

26. Kirshenbaum, K. et al. Pressure-Induced Unconventional Superconducting Phase in the Topological

12

Insulator Bi2Se3. Phys. Rev. Lett. 111, 087001, (2013).

27. Kamm, G. N., Gillespie, D. J., Ehrlich, A. C., Wieting, T. J. & Levy, F. Fermi surface, effective

masses, and Dingle temperatures of ZrTe5 as derived from the Shubnikov-de Haas effect. Phys. Rev.

B 31, 7617-7623, (1985).

28. Fjellvåg, H. & Kjekshus, A. Structural properties of ZrTe5 and HfTe5 as seen by powder diffraction.

Solid State Commun. 60, 91-93, (1986).

29. Mao, H. K., Xu, J. & Bell, P. M. Calibration of the ruby pressure gauge to 800 kbar under quasi-

hydrostatic conditions. J. Geophys. Res. 91, 4673-4676, (1986).

30. Blaha, P., Schwarz, K., Madsen, G., Kvasicka, D. & Luitz, J. WIEN2k, An Augmented Plane Wave

Plus Local Orbitals Program for Calculating Crystal Properties. (2001).

31. McIlroy, D. N. et al. Observation of a semimetal-semiconductor phase transition in the intermetallic

ZrTe5. J. Phys.: Condens. Matter 16, L359, (2004).

32. Pavlosiuk, O., Kaczorowski, D. & Wiśniewski, P. Shubnikov-de Haas oscillations, weak

antilocalization effect and large linear magnetoresistance in the putative topological superconductor

LuPdBi. Sci. Rep. 5, 9158, (2015).

33. Werthamer, N. R., Helfand, E. & Hohenberg, P. C. Temperature and Purity Dependence of the

Superconducting Critical Field, Hc2. III. Electron Spin and Spin-Orbit Effects. Phys. Rev. 147, 295-

302, (1966).

34. Nikitin, A. M. et al. Magnetic and superconducting phase diagram of the half-Heusler topological

semimetal HoPdBi. Preprint at http://arXiv.org/abs/1504.03181 (2015).

35. Murnaghan, F. D. The Compressibility of Media under Extreme Pressures. Proc. Natl. Acad. Sci.

USA 30, 244-247, (1944).

36. Pan, X.-C. et al. Pressure-induced superconductivity in WTe2. Preprint at http://arXiv.org/abs/

1501.07394 (2015).

37. Ataca, C., Topsakal, M., Aktürk, E. & Ciraci, S. A Comparative Study of Lattice Dynamics of Three-

and Two-Dimensional MoS2. J. Phys. Chem. C 115, 16354-16361, (2011).

38. Fu, L. & Berg, E. Odd-Parity Topological Superconductors: Theory and Application to CuxBi2Se3.

Phys. Rev. Lett. 105, 097001, (2010).

39. Wan, X. & Savrasov, S. Y. Turning a band insulator into an exotic superconductor. Nat. Commun. 5,

4144, (2014).

Acknowledgements

This research was financially supported by the National Key Basic Research of

China Grants No. 2011CBA00111 and the National Natural Science Foundation of

China Grants (Nos. U1332143, 11374137).

13

Figure 1. Experimental evidence for the pressure-induced superconductivity in

ZrTe5 single crystal. (a) Temperature-dependent resistance R(T) at pressures up to 3.9

GPa in the whole temperature range. (b) Magnetoresistance at the peak temperature of

resistance anomaly at different pressures. (c) The emergence of pressure-induced

superconducting transition at higher pressures from 6.2 GPa to 68.5 GPa. (d) The real

part of ac magnetic susceptibility as a function of temperature at different pressures.

The inset of Fig. 1(a) illustrates how the pressure, magnetic field and current are applied.

The inset of Fig. 1(d) is the image of experimental setup for ac magnetic susceptibility

measurement.

14

Figure 2. Temperature dependence of resistance at low temperatures in the whole

investigated pressure range. (a) The first sharp resistance drop can be seen as the

manifestation of superconductivity at 6.7 GPa. The superconducting transition

temperature Tc is defined by the 50% drop of the normal state resistance. With

increasing pressure, the Tc increases monotonously towards 17.8 GPa. (b) Above 21.2

GPa, a higher transition emerges around 6.0 K, suggesting a novel superconducting

phase. Here, the Tc symbols the onset of the superconducting transition (see the text).

15

Figure 3. Temperature dependence of upper critical field μ0Hc2(T) with magnetic

field parallel to the b-axis. (a,c) Temperature dependence of resistance under different

magnetic fields up to 1.5 T at 14.6 GPa and up to 1.0 T at 30.0 GPa, respectively. Here,

superconducting transition temperature Tc at different magnetic fields are determined

by 50% and 90% drop of the normal state resistance, respectively. (b,d)

Superconducting transition temperature dependence of the upper critical field μ0Hc2 at

14.6 GPa and 30.0 GPa, respectively. The dashed lines represent the fitting lines based

on the Werthamer-Helfand-Hohenberg (WHH) formula.

16

Figure 4. Temperature-pressure phase diagram of ZrTe5 single crystal. T* denotes

the peak temperature of resistance anomaly. The magenta region corresponds to SC-I

phase where Tc is defined as 50% drop of the normal state resistance. The green region

corresponds to SC-II phase where the Tc is determined as the onset temperature of

resistance drop. The pentagram represents the onset temperature of Meissner effect in

the ac magnetic susceptibility measurements. The rhomb and down triangle represent

the peak temperature of resistance anomaly and onset temperature of resistance drop at

pressures with Daphne 7373 oil as the pressure-transmitting medium. The inset shows

the specific resistance as a function of applied pressure at 10 K and 300 K, respectively.

17

Figure 5. The band structure and Fermi surface of ZrTe5 at 7.0 GPa and 20.0 GPa.

(a) and (c) are the band structure and Fermi surface of ZrTe5 at 7.0 GPa, respectively.

(b) and (d) are the band structure and Fermi surface of ZrTe5 at 20.0 GPa, respectively.