arXiv subjects

Juefei Wu

Publications and source records attributed to Juefei Wu.

32 records · Page 2Linked to original sources

arXiv2023

Pressure-induced structure phase transitions and superconductivity in dual topological insulator BiTe

The (Bi2)m(Bi2Te3)n homologous series possess natural multilayer heterostructure with intriguing physical properties at ambient pressure. Herein, we report the pressure-dependent evolution of the structure and electrical transport of the dual topological insulator BiTe, a member of the (Bi2)m(Bi2Te3)n series. With applied pressure, BiTe exhibits several different crystal structures and distinct superconducting states, which is remarkably similar to other members of the (Bi2)m(Bi2Te3)n series. Our results provide a systematic phase diagram for the pressure-induced superconductivity in BiTe, contributing to the highly interesting physics in this (Bi2)m(Bi2Te3)n series.

cond-mat.supr-con↗

arXiv2023

Pressure-induced Superconductivity in Tellurium Single Crystal

Tellurium (Te) is one of the p-orbital chalcogens, which shows attractive physical properties at ambient pressure. Here, we systematically investigate both structural and electronic evolution of Te single crystal under high pressure up to 40 GPa. The pressure dependence of the experimental Raman spectrum reveals the occurrence of multiple phase transitions, which is consistent with highpressure synchrotron X-ray diffraction (XRD) measurements. The appearance of superconductivity in high-pressure phase of Te is accompanied by structural phase transitions. The high-pressure phases of Te reveal a nonmonotonic evolution of superconducting temperature Tc with notably different upper critical fields. The theoretical calculations demonstrate that the pressure dependence of the density of states(DOS) agrees well with the variation of Tc. Our results provide a systematic phase diagram for the pressure-induced superconductivity of Te.

cond-mat.supr-con↗

arXiv2023

Superconducting Ternary Hydridies in Ca-U-H under High Pressure

The research on hydrogen-rich ternary compounds attract tremendous attention for it paves new route to room-temperature superconductivity at lower pressures. Here, we study the crystal structures, electronic structures, and superconducting properties of the ternary Ca-U-H system, combining crystal structure predictions with ab-initio calculations under high pressure. We found four dynamically stable structures with hydrogen clathrate cages: CaUH12-Cmmm, CaUH12-Fd-3m, Ca2UH18-P-3m1, and CaU3H32-Pm-3m. Among them, the Ca2UH18-P-3m1 and CaU3H32-Pm-3m are likely to be synthesized below 1 megabar. The f electrons in U atoms make dominant contribution to the electronic density of states around the Fermi energy. The electron-phonon interaction calculations reveal that phonon softening in the mid-frequency region can enhance the electron-phonon coupling significantly. The Tc value of Ca2UH18-P-3m1 is estimated to be 57.5-65.8 K at 100 GPa. Our studies demonstrate that introducing actinides into alkaline-earth metal hydrides provides possibility in designing novel superconducting ternary hydrides.

cond-mat.supr-con↗

arXiv2023

Pressure-induced Superconductivity and Structure Phase Transition in SnAs-based Zintl Compound SrSn2As2

Layered SnAs-based Zintl compounds exhibit a distinctive electronic structure, igniting extensive research efforts in areas of superconductivity, topological insulators and quantum magnetism. In this paper, we systematically investigate the crystal structures and electronic properties of the Zintl compound SrSn2As2 under high-pressure. At approximately 20.8 GPa, pressure-induced superconductivity is observed in SrSn2As2 with a characteristic dome-like evolution of Tc. Theoretical calculations together with high pressure synchrotron X-ray diffraction and Raman spectroscopy have identified that SrSn2As2 undergoes a structural transformation from a trigonal to a monoclinic structure. Beyond 28.3 GPa, the superconducting transition temperature is suppressed due to a reduction of the density of state at the Fermi level. The discovery of pressure-induced superconductivity, accompanied by structural transitions in SrSn2As2, greatly expands the physical properties of layered SnAs-based compounds and provides a new ground states upon compression.

cond-mat.supr-con↗

arXiv2023

Pressure-induced Superconductivity and Topological Quantum Phase Transitions in the Topological Semimetal ZrTe2

Topological transition metal dichalcogenides (TMDCs) have attracted much attention due to its potential applications in spintronics and quantum computations. In this work, we systematically investigate the structural and electronic properties of topological TMDCs candidate ZrTe2 under high pressure. A pressure-induced Lifshitz transition is evidenced by the change of charge carrier type as well as the Fermi surface. Superconductivity was observed at around 8.3 GPa without structural phase transition. A typical dome-shape phase diagram is obtained with the maximum Tc of 5.6 K for ZrTe2. Furthermore, our theoretical calculations suggest the presence of multiple pressure-induced topological quantum phase transitions, which coexists with emergence of superconductivity. The results demonstrate that ZrTe2 with nontrivial topology of electronic states display new ground states upon compression.

cond-mat.supr-con↗

arXiv2023

Effects of Pressure and Doping on Ruddlesden-Popper phases Lan+1NinO3n+1

Recently the discovery of superconductivity with a critical temperature Tc up to 80 K in Ruddlesden-Popper phases Lan+1NinO3n+1 (n = 2) under pressure has garnered considerable attention. Up to now, the superconductivity was only observed in La3Ni2O7 single crystal grown with the optical-image floating zone furnace under oxygen pressure. It remains to be understood the effect of chemical doping on superconducting La3Ni2O7 as well as other Ruddlesden-Popper phases. Here, we systematically investigate the effect of external pressure and chemical doping on polycrystalline Ruddlesden-Popper phases. Our results demonstrate the application of pressure and doping effectively tunes the transport properties of Ruddlesden-Popper phases. We find pressure-induced superconductivity up to 86 K in La3Ni2O7 polycrystalline sample, while no signatures of superconductivity are observed in La2NiO4 and La4Ni3O10 systems under high pressure up to 50 GPa. Our study sheds light on the exploration of high-Tc superconductivity in nickelates.

cond-mat.supr-con↗

arXiv2023

Pressure-induced Superconductivity in Zintl Topological Insulator SrIn2As2

The Zintl compound AIn2X2 (A = Ca, Sr, and X = P, As), as a theoretically predicted new non-magnetic topological insulator, requires experiments to understand their electronic structure and topological characteristics. In this paper, we systematically investigate the crystal structures and electronic properties of the Zintl compound SrIn2As2 under both ambient and high-pressure conditions. Based on systematic angle-resolved photoemission spectroscopy (ARPES) measurements, we observed the topological surface states on its (001) surface as predicted by calculations, indicating that SrIn2As2 is a strong topological insulator. Interestingly, application of pressure effectively tuned the crystal structure and electronic properties of SrIn2As2. Superconductivity is observed in SrIn2As2 for pressure where the temperature dependence of the resistivity changes from a semiconducting-like behavior to that of a metal. The observation of nontrivial topological states and pressure-induced superconductivity in SrIn2As2 provides crucial insights into the relationship between topology and superconductivity, as well as stimulates further studies of superconductivity in topological materials.

cond-mat.supr-con↗

arXiv2023

Robust anomalous Hall effect in ferromagnetic metal under high pressure

Recently, the giant intrinsic anomalous Hall effect (AHE) has been observed in the materials with kagome lattice. In this study, we systematically investigate the influence of high pressure on the AHE in the ferromagnet LiMn6Sn6 with clean Mn kagome lattice. Our in-situ high-pressure Raman spectroscopy indicates that the crystal structure of LiMn6Sn6 maintains a hexagonal phase under high pressures up to 8.51 GPa. The anomalous Hall conductivity (AHC) σxyA remains around 150 Ω-1 cm-1, dominated by the intrinsic mechanism. Combined with theoretical calculations, our results indicate that the stable AHE under pressure in LiMn6Sn6 originates from the robust electronic and magnetic structure.

cond-mat.mtrl-sci↗

arXiv2023

Pressure-tunable magnetic topological phases in magnetic topological insulator MnSb4Te7

Magnetic topological insulators, possessing both magnetic order and topological electronic structure, provides an excellent platform to research unusual physical properties. Here, we report a high-pressure study on the anomalous Hall effect of magnetic TI MnSb4Te7 through transports measurements combined with first-principle theoretical calculations. We discover that the ground state of MnSb4Te7 experiences a magnetic phase transition from the A-type antiferromagnetic state to ferromagnetic dominating state at 3.78 GPa, although its crystal sustains a rhombohedral phase under high pressures up to 8 GPa. The anomalous Hall conductance σxyA keeps around 10 Ω-1 cm-1, dominated by the intrinsic mechanism even after the magnetic phase transition. The results shed light on the intriguing magnetism in MnSb4Te7 and pave the way for further studies of the relationship between topology and magnetism in topological materials.

cond-mat.supr-con↗

arXiv2017

Silicon clathrates for photovoltaics predicted by a two-step crystal structure search

Silicon in a cubic diamond structure currently plays a significant role in the photovoltaic industry. However, the intrinsic band structures of crystalline silicon restrict its sunlight conversion efficiency. Recently, a clathrate-like Si-24 has been successfully synthesized, which has a quasi-direct bandgap and sheds light on silicon-based photovoltaics. Here, we proposed a two-step crystal structure search method based on first-principles calculations and explored silicon clathrate structures extensively. First, the guest-host compounds were searched at high pressure, and then, the porous guest-free silicon clathrates were obtained by removing the guest atoms. Using potassium as the guest atom, we identified four metastable silicon clathrate structures, and some of them have bandgaps close to the optimal range of the Shockley-Queisser limit and have a better absorption rate than the cubic diamond silicon. These silicon clathrates may have promising value in photovoltaic applications.

cond-mat.mtrl-sci↗

arXiv2017

High-pressure phases of Weyl semimetals NbP, NbAs, TaP and TaAs

The high pressure phase diagrams of TaAs family (NbP, NbAs, TaP and TaAs) are explored systematically using crystal structure search together with first-principles calculations. Our calculations show that NbAs and TaAs have similar phase diagrams and possess the same structural phase transition sequence of I41md $\rightarrow$ P-6m2 $\rightarrow$ P21/c $\rightarrow$ Pm-3m, with a bit different transition pressures. The phase transition sequence of NbP and TaP are somewhat different from that of NbAs and TaAs. In which new structures emerge, for instance, the Cmcm structure in NbP and the Pmmn structure in TaP. It is found interestingly that in the electronic structure of the high-pressure phase P-6m2-NbAs, there are Weyl points and triple degenerate points coexisted, similar to the high-pressure P-6m2-TaAs.

cond-mat.mtrl-sci↗

arXiv2017

Strain-induced quantum topological phase transitions in Na3Bi

Strain can be used as an effective tool to tune the crystal structure of materials and hence to modify their electronic structures, including topological properties. Here, taking Na3Bi as a paradigmatic example, we demonstrated with first-principles calculations and k$\cdot$p models that the topological phase transitions can be induced by various types of strains. For instance, the Dirac semimetal phase of ambient Na3Bi can be tuned into a topological insulator (TI) phase by uniaxial strain along the h100i axis. Hydrostatic pressure can let the ambient structure transfer into a new thermodynamically stable phase with Fm-3m symmetry, coming with a perfect parabolic semimetal having a single contact point between the conduction and valence bands, exactly at $Γ$ point on the Fermi level like $α$-Sn. Furthermore, uniaxial strain in the <100> direction can tune the new parabolic semimetal phase into a Dirac semimetal, while shear strains in both the <100> and <111> directions can take the new parabolic semimetal phase into a TI. k$\cdot$p models are constructed to gain more insights into these quantum topological phase transitions. At last, we calculated surface states of Fm-3m Na3Bi without and with strains to verify these topological transitions.

cond-mat.mtrl-sci↗

arXiv2016

Origin of the superconductivity of WTe2 under pressure

Tungsten ditelluride (WTe2) has attracted significant attention due to its interesting electronic properties, such as the unsaturated magnetoresistance and superconductivity. Recently, it has been proposed to be a new type of Weyl semimetal, which is distinguished from other transition metal dichalcogenides (TMDs) from a topological prospective. Here, we study the structure of WTe2 under pressure with a crystal structure prediction and ab initio calculations combined with high pressure synchrotron X-ray diffraction and Raman spectroscopy measurements. We find that the ambient orthorhombic structure (Td) transforms into a monoclinic structure (1T') at around 4-5 GPa. As the transition pressure is very close to the critical point in recent high-pressure electrical transport measurements, the emergence of superconductivity in WTe2 under pressure is attributed to the Td-1T' structure phase transition, which associates with a sliding mechanism of the TMD layers and results in a shorter Te-Te interlayer distance compared to the intralayer ones. These results highlight the critical role of the interlayer stacking and chalcogen interactions on the electronic and superconducting properties of multilayered TMDs under hydrostatic strain environments.

cond-mat.mtrl-sci↗

arXiv2015

Pressure-induced semimetal to superconductor transition in a three-dimensional topological material ZrTe5

As a new type of topological materials, ZrTe5 shows many exotic properties under extreme conditions. Utilizing resistance and ac magnetic susceptibility measurements under high pressure, while the resistance anomaly near 128 K is completely suppressed at 6.2 GPa, a fully superconducting transition emerges surprisingly. The superconducting transition temperature Tc increases with applied pressure, and reaches a maximum of 4.0 K at 14.6 GPa, followed by a slight drop but remaining almost constant value up to 68.5 GPa. At pressures above 21.2 GPa, a second superconducting phase with the maximum Tc of about 6.0 K appears and coexists with the original one to the maximum pressure studied in this work. In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopy combined with theoretical calculations indicate the observed two-stage superconducting behavior is correlated to the structural phase transition from ambient Cmcm phase to high-pressure C2/m phase around 6 GPa, and to a mixture of two high-pressure phases of C2/m and P-1 above 20 GPa. The combination of structure, transport measurement and theoretical calculations enable a complete understanding of the emerging exotic properties in three-dimensional topological materials happened under extreme environments.

cond-mat.supr-con↗