Two distinct charge density wave orders and emergent superconductivity in pressurized CuTe Shuyang Wang125 Qing Wang125 Chao An4 Yonghui Zhou123 Ying Zhou 4 Xuliang Chen 陈绪

2025-05-06 0 0 831.43KB 21 页 10玖币

侵权投诉

Two distinct charge density wave orders and emergent superconductivity

in pressurized CuTe

Shuyang Wang,1,2,5 Qing Wang,1,2,5 Chao An,4 Yonghui Zhou,1,2,3 Ying Zhou,4 Xuliang Chen (陈绪

亮),1,2,3,6,* Ning Hao,1,2,3,* and Zhaorong Yang1,2,3,4,*

1Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic

Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, China

2Science Island Branch of Graduate School, University of Science and Technology of China, Hefei

230026, China

3Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China

4Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China

5These authors contributed equally

6Lead Contact

*Correspondence: xlchen@hmfl.ac.cn (X.C.); haon@hmfl.ac.cn (N.H.); zryang@issp.ac.cn (Z.Y.)

Keywords: high pressure, ultralow temperature, charge density waves, superconductivity, electron

correlation

SUMMARY

The discovery of multiple charge-density-wave (CDW) orders in superconducting

cuprates and Kagome CsV3Sb5 has offered a unique milieu for studying the interplay

of CDW and superconductivity and altered our perspective on their nature. Here, we

report a high-pressure study of quasi-one-dimensional CDW material CuTe through

ultralow-temperature (400 mK) electrical transport and temperature-dependent Raman

spectroscopy measurements and first-principles calculations. We provide solid

evidence that the pristine CDW order (CDW1) transforms into a distinct CDW order

(CDW2) at ~6.5 GPa. Calculations show that the driving force of CDW1 is due to the

nesting effect and that of CDW2 probably arises from the electronic correlated

interaction. Strikingly, pressure-induced superconductivity is observed with a

dome-like phase diagram and its transition displays an extraordinary broadening along

with the crossover from CDW1 to CDW2. These results demonstrate that pressurized

CuTe provides a promising playground for understanding the intricated interplay of

multiple CDWs and superconductivity.

INTRODUCTION

Understanding the interplay between superconductivity and other collective electronic

phenomena has always been one of the central issues within the condensed-matter and

material-physics communities.1-5 An example is the interplay between

superconductivity and the charge-density-wave (CDW) order in low-dimensional

materials.6,7 Intuitively, superconductivity should be favored by suppressing the CDW

because the closure of the CDW energy gap contributes more charge carriers and

increases the density of states at the Fermi surface within the

Bardeen-Cooper-Schrieffer scenario.8,9 However, in real materials, the relationship

between superconductivity and CDW is very complicated, involving coexistence,

competition, and cooperation under external tuning parameters like doping,

intercalation, or pressure.7,10-24 For example, TiSe2 and TaS2 are both prototypical

CDW transition-metal dichalcogenides. With the application of pressure,

superconductivity is found to emerge near the CDW quantum critical point in the

former case11 while it seems to be independent of the CDW order in the latter case.12

In a recently discovered kagome superconductor, CsV3Sb5, a double-dome-like

superconducting phase diagram is observed with unusual interplay between

superconductivity and CDW under high pressure, and moreover a new dome-like

superconducting phase reemerges after the vanishing of the CDW upon further

compression.13-19

CuTe, as a two-dimensional layered material, has received much recent attention25-31

because it displays a quasi-one-dimensional CDW order below ~346 K. In the

high-temperature non-CDW state, CuTe has a Pmmn (SG. 59) structure, consisting of

wrinkled Cu planes sandwiched in an array of quasi-one-dimensional Te chains. Upon

cooling below the CDW transition temperature TCDW, a periodic lattice modulation

occurs within the quasi-one-dimensional Te chains.25,26 At the same time, a CDW

energy gap opens up due to the well-nested quasi-one-dimensional Fermi surface

sheets contributed by px orbitals of Te.26,30 Associated with formation of the CDW

order, the Raman spectra of CuTe exhibit one collective amplitude mode and four

zone-folded (ZF) modes in addition to two phonon modes.30 Our recent high-pressure

investigation of CuTe showed that the application of pressure can effectively suppress

the CDW order.31 Moreover, at a high pressure far above the critical pressure where

the CDW disappears, superconductivity is induced due to a structural phase

transition.31 Interestingly, the preliminary electrical transport (1.8-300 K) in the

intermediate pressure region reveals subtle modification of the CDW order—the

resistivity anomaly related to the CDW transition changes its shape at a characteristic

pressure.31

Here, we provide solid evidence by combined electrical transport and Raman

spectroscopy measurements that the pristine CDW order (CDW1) transforms to a

distinct CDW order (CDW2) at ca. 6.5 GPa. Furthermore, by extending the

temperature down to sub-kelvin, we found pressure-induced superconductivity at ca.

4.8 GPa along with suppression of the CDW1, and the superconducting transition

displays anomalous broadening below 10 GPa relating to the crossover from CDW1

to CDW2. According to the calculations, the birth of CDW2 accompanies the

emergence of four small isotropic hole-like Fermi pockets with nearly full weight of

pz orbital of Te atoms. In comparison with several different mechanisms for CDW

orders, we argue that the CDW2 could be driven by the electronic correlated

interaction.

RESULTS AND DISCUSSION

Transport evidence for pressure-induced new CDW and superconductivity

Figure 1A shows the temperature dependence of resistivity (ρ) for a CuTe single

crystal with temperatures down to 400 mK under various pressures up to 13.8 GPa. In

the low-pressure range, the original CDW transition leads to a hump-like anomaly at

TCDW in the ρ(T) curve and shows as a dip in the corresponding derivative dρ/dT curve

(see Figure 1B). Here, TCDW is defined as the onset temperature of anomalies

observed in dρ/dT upon cooling. In agreement with our previous work,31 Figure 1A

uncovers an unusual pressure-dependent evolution of the CDW order. The resistivity

hump gets suppressed gradually with increasing pressure up to 6.7 GPa, indicating

suppression of the CDW under pressure. However, as the pressure is increased to 8.1

GPa, one can see that the anomaly in dρ/dT changes its profile from the original dip to

a peak. This observation signals a subtle modification of the CDW order as in the case

of pressurized CsV3Sb5.13-15 In the pressurized CsV3Sb5, the TCDW decreases

monotonically with increasing pressure across the crossover region,13-15 while in the

pressurized CuTe the TCDW jumps to a higher temperature at the critical pressure. The

peak-like anomaly in dρ/dT shifts to lower temperatures upon further compression

and is scarcely observed beyond 9.5 GPa. These unusual evolutions of the CDW are

captured in other independent runs, as shown in Figure S1, indicating the

reproducibility of the results. We also measured Hall resistivity at 5 K and various

pressures (see Figure S2). At 0.8 GPa, the Hall resistivity shows quasi-linear field

dependence with positive slope, which indicates that hole-type carriers dominate the

transport behavior, consistent with the investigations of CuTe at ambient pressure.28,30

With increasing pressure, the slope of ρyx(H) first increases and then decreases

followed by a sign change between 6.7 and 8.1 GPa.

In addition, by lowering temperature down to 400 mK, we demonstrate that

superconductivity is induced, accompanied by the suppression of the pristine CDW

order. Figure. 1C shows an enlarged view of the ρ(T) data below 3 K, highlighting a

non-monotonic evolution of the superconducting transition with increasing pressure.

A very small drop in resistivity starts to appear at 4.8 GPa with an onset temperature

of TConset ~0.5 K; zero resistance is observed at 5.7 GPa. This pressure-induced

superconducting transition is also confirmed by the temperature dependence of

resistivity under external magnetic fields at 5.7 GPa (Figure S3), from which the

upper critical field at zero temperature is estimated to be 1260 Oe. However, in the

pressure range of 5.7-9.5 GPa, the superconducting transition presents an anomalous

broadening with ΔTC=TConset-TCzero of ~2 K. These observations are confirmed in other

runs, as shown in Figure S4. The broadened superconducting transition is also

reminiscent of that in pressurized CsV3Sb5, in which the anomalous behavior is

attributed to strong competition between superconductivity and the newly appeared

CDW order.13-15 As discussed above, CuTe also exhibits a signature of CDW

transformation under pressure. By coincidence, the superconducting transition in

pressurized CuTe becomes sharp when the peak-like anomaly in T associated with the

CDW transition is hard to discern.

Raman spectroscopy measurements under high pressure and low temperature

To further study the evolution of CDW in CuTe, we performed high-pressure Raman

experiments at temperatures between 70 and 320 K, as shown in Figure 2. At ambient

pressure, there are one collective amplitude mode and four ZF modes which are

associated with the CDW order.30 The amplitude mode is a soft-phonon mode coupled

to the electronic density at the CDW wavevector and dressed by the amplitude

fluctuations of the CDW order parameter, which is a fingerprint of the CDW

order.32-34 The ZF modes correspond to normal phonons folded to the center of the

Brillouin zone. At 1.5 GPa and 70 K, the Raman spectrum consists of six peaks (see

Figure 2A). According to Ref. 30, these peaks can be assigned to two phonon modes,

Ag1 (130.8 cm-1) and Ag2 (142.7 cm-1), one CDW amplitude mode (52.7 cm-1), and

two ZF modes (74.2 and 123.9 cm-1). As expected, the amplitude mode softens

rapidly upon warming while the ZF modes move at a much slower rate, as shown in

Figure 2C. The temperature-dependent frequency of the amplitude mode can be well

fitted by a modified mean-field (MMF) model,30,35 from which TCDW is estimated to

be 285 K at 1.5 GPa (Figure 2J).

With increasing pressure, as shown in Figures 2C-2F, the CDW amplitude mode at 70

K shifts gradually to lower frequencies and is undetectable at 6.5 GPa; at the same

time, its intensity becomes steadily weaker. TCDW, deduced from fits to the MMF

model of the temperature evolution of the amplitude mode at each pressure, decreases

monotonically under pressure, indicative of suppression of the pristine CDW order

(Figures 2J-2L). At 6.5 GPa, the spectrum contains only two Ag modes in the whole

measured temperature range (Figure 2F). It is interesting to note that the suppression

of the pristine CDW order up to 6.5 GPa seen in the Raman spectra is consistent with

that reflected in the electronic transport measurements. And more strikingly, as the

pressure is increased to 8.5 GPa, two sets of peaks with CDW character reappear,

which is in line with the above conjecture of a CDW transformation. One set of peaks

displays a rapid softening with increasing temperature, as shown in Figures 2B and

2G, characteristic of the CDW amplitude mode. The temperature dependence of peak

frequency for the emergent CDW can also be fitted by the MMF model, which gives a

TCDW of 134 K at 8.5 GPa (Figure 2M). The other set can be assigned to the ZF mode,

because its peak position is insensitive to temperature from 70 to 140 K. With further

increase of the pressure beyond 9.5 GPa, both the CDW amplitude mode and the ZF

mode disappear (Figure 2I), also in agreement with the vanishing of the resistivity

anomaly (Figure 1).

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TwodistinctchargedensitywaveordersandemergentsuperconductivityinpressurizedCuTeShuyangWang,1,2,5QingWang,1,2,5ChaoAn,4YonghuiZhou,1,2,3YingZhou,4XuliangChen(陈绪亮),1,2,3,6,*NingHao,1,2,3,*andZhaorongYang1,2,3,4,*1AnhuiProvinceKeyLaboratoryofCondensedMatterPhysicsatExtremeConditions,HighMagneticFieldLa...

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Two distinct charge density wave orders and emergent superconductivity in pressurized CuTe Shuyang Wang125 Qing Wang125 Chao An4 Yonghui Zhou123 Ying Zhou 4 Xuliang Chen 陈绪.pdf

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Two distinct charge density wave orders and emergent superconductivity in pressurized CuTe Shuyang Wang125 Qing Wang125 Chao An4 Yonghui Zhou123 Ying Zhou 4 Xuliang Chen 陈绪

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