arXiv subjects

P. T. Yang

Publications and source records attributed to P. T. Yang.

7 recordsLinked to original sources

arXiv2023

Emergence of high-temperature superconducting phase in the pressurized La3Ni2O7 crystals

The recent report of pressure-induced structure transition and signature of superconductivity with Tc = 80 K above 14 GPa in the La3Ni2O7 crystals has garnered considerable attention. To further elaborate this discovery, we carried out comprehensive resistance measurements on the La3Ni2O7 crystals grown with the optical-image floating zone furnace under oxygen pressure (15 bar) by using the diamond anvil cell (DAC) and cubic anvil cell (CAC), which employs the solid and liquid pressure transmitting medium, respectively. For the sample #1 measured in DAC, it exhibits a semiconducting-like behavior with large resistance at low pressures and becomes metallic gradually upon compression. At the pressures P >= 13.7 GPa, we observed the appearance of resistance drop as large as ~50% around 70 K, which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field. These observations are consistent with the recent report mentioned above. On the other hand, the sample #2 measured in CAC retains the metallic behavior in the investigated pressure range up to 15 GPa. The hump-like anomaly in resistance around ~130 K at ambient pressure disappears at P >= 2 GPa. In the pressure range from 11 to 15 GPa, we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures, which evolves into a pronounced drop of resistance by 98% below 62 K at 15 GPa, reaching a temperature-independent resistance of 20 uOhm below 20 K. Similarly, this resistance anomaly can be shifted to lower temperatures progressively by applying external magnetic fields, resembling a typical superconducting transition.

cond-mat.supr-con↗

arXiv2023

Superconductivity up to 17 K in the high-pressure rhombohedral-I phase of ReO3: a potential oxide analogy of hydride superconductors

As an A-site-vacant perovskite-type oxide, ReO3 undergoes sequential pressure-driven structural transitions associated with the rotation of ReO6 octahedra. The rhombohedral-I phase in the pressure range of 12-39 GPa is featured by a lattice of nearly close-packed oxygen layers intercalated with Re cations, in reminiscent of the recently discovered superhydride superconductors. A combined study of first-principles calculations and transport measurements under high pressures enabled us to discover superconductivity in the rhombohedral-I phase, and it shows a dome-shaped Tc(P) with a maximum Tc of 17 K at about 30 GPa. In addition to the enhanced density of states at Fermi level compared to that of the ambient phase, the vibrations of hexagonal-close-packed oxygen lattice significantly strengthen the electron-phonon coupling, which is responsible for observed superconductivity with a relatively high Tc. The present work thus establishes a rare case among oxide superconductors that the light-element oxygen lattice plays a crucial role in inducing superconductivity.

cond-mat.supr-con↗

arXiv2022

Emergence of superconductivity on the border of antiferromagnetic order in RbMn6Bi5 under high pressure: A new family of Mn-based superconductors

The advances in the field of unconventional superconductivity are largely driven by the discovery of novel superconducting systems. Here we report on the discovery of superconductivity on the border of antiferromagnetic order in a quasi-one-dimensional RbMn6Bi5 via measurements of resistivity and magnetic susceptibility under high pressures. With increasing pressure, its antiferromagnetic transition with TN = 83 K at ambient pressure is first enhanced moderately and then suppressed completely at a critical pressure of Pc = 13 GPa, around which bulk superconductivity emerges and exhibits a dome-like Tc(P) with a maximal Tc_onset = 9.5 K at about 15 GPa. Its temperature-pressure phase diagram resembles those of many magnetism-mediated superconducting systems. In addition, the superconducting state around Pc is characterized by a large upper critical field μ0Hc2(0) exceeding the Pauli limit, elaborating a possible unconventional paring mechanism. The present study, together with our recent work on KMn6Bi5 (Tcmax = 9.3 K), makes AMn6Bi5 (A= Alkali metal) a new family of Mn-based superconductors with relatively high Tc.

cond-mat.supr-con↗

arXiv2022

Pressure-induced superconductivity up to 9 K in the quasi-one-dimensional KMn6Bi5

The Mn-based superconductor is rare owing to the strong magnetic pair-breaking effect. Here we report on the discovery of pressure-induced superconductivity in KMn6Bi5, which becomes the first ternary Mn-based superconductor. At ambient pressure, the quasi-one-dimensional KMn6Bi5 is an antiferromagnetic metal with TN = 75 K. By measuring resistivity and ac magnetic susceptibility under hydrostatic pressures up to 14.2 GPa in a cubic anvil cell apparatus, we find that its antiferromagnetic transition can be suppressed completely at a critical pressure of Pc = 13 GPa, around which bulk superconductivity emerges and displays a superconducting dome with the maximal Tconset = 9.3 K achieved at about 14.2 GPa. The close proximity of superconductivity to a magnetic instability in the temperature-pressure phase diagram of KMn6Bi5 and an unusually large μ0Hc2(0) = 18.9 T exceeding the Pauli limit suggests an unconventional magnetism-mediated paring mechanism. In contrast to the binary MnP, the flexibility of the crystal structure and chemical compositions in the ternary AMn6Bi5 (A = alkali metal) can open a new avenue for finding more Mn-based superconductors.

cond-mat.supr-con↗

arXiv2021

Quasi-one-dimensional superconductivity in the pressurized charge-density-wave conductor HfTe3

HfTe3 single crystal undergoes a charge-density-wave (CDW) transition at TCDW = 93 K without the appearance of superconductivity (SC) down to 50 mK at ambient pressure. Here, we determined its CDW vector q = 0.91(1) a* + 0.27(1) c* via low-temperature transimission electron microscope and then performed comprehensive high-pressure transport measurements along three major crystallographic axes. Our results indicate that the superconducting pairing starts to occur within the quasi-one-dimensional (Q1D) -Te2-Te3- chain at 4-5 K but the phase coherence between the superconducting chains cannot be realized along either the b- or c-axis down to at least 1.4 K, giving rise to an extremely anisotropic SC rarely seen in real materials. We have discussed the prominent Q1D SC in pressurized HfTe3 in terms of the anisotropic Fermi surfaces arising from the unidirectional Te-5px electronic states and the local pairs formed along the -Te2-Te3- chains based on the first-principles electronic structure calculations.

cond-mat.supr-con↗

arXiv2021

Superconductivity at ~70 K in Tin Hydride SnHx under High Pressure

Various tin hydrides SnHx (x = 4, 8, 12, 14) have been theoretically predicted to be stable at high pressures and to show high-critical-temperature superconductivity with Tc ranging from about 70 to 100 K. However, experimental verifications for any of these phases are still lacking to date. Here, we report on the in-situ synthesis, electrical resistance, and synchrotron x-ray diffraction measurements of SnHx at ~ 200 GPa. The main phase of the obtained sample can be indexed with the monoclinic C2/m SnH12 via comparison with the theoretical structural modes. A sudden drop of resistance and the systematic downward shift under external magnetic fields signals the occurrence of superconductivity in SnHx at Tc = ~ 70 K with an upper critical field u0Hc2(0) = ~ 11.2 T, which is relatively low in comparison with other reported high-Tc superhydrides. Various characteristic superconducting parameters are estimated based on the BCS theory.

cond-mat.supr-con↗

arXiv2020

Metal-to-metal transition and heavy-electron state in Nd$_4$Ni$_3$O$_{10-δ}$

The trilayer nickelate Nd$_4$Ni$_3$O$_{10-δ}$ ($δ\approx$ 0.15) was investigated by the measurements of x-ray diffraction, electrical resistivity, magnetic susceptibility, and heat capacity. The crystal structure data suggest a higher Ni valence in the inner perovskite-like layer. At ambient pressure the resistivity shows a jump at 162 K, indicating a metal-to-metal transition (MMT). The MMT is also characterized by a magnetic susceptibility drop, a sharp specific-heat peak, and an isotropic lattice contraction. Below $\sim$ 50 K, a resistivity upturn with a log$T$ dependence shows up, accompanying with a negative thermal expansion. External hydrostatic pressure suppresses the resistivity jump progressively, coincident with the diminution of the log$T$ behavior. The low-temperature electronic specific-heat coefficient is extracted to be $\sim$ 150 mJ K$^{-2}$ mol-fu$^{-1}$, equivalent to $\sim$ 50 mJ K$^{-2}$ mol-Ni$^{-1}$, indicating an unusual heavy-electron correlated state. The novel heavy-electron state as well as the logarithmic temperature dependence of resistivity is explained in terms of the Ni$^{3+}$ centered Kondo effect in the inner layer of the (NdNiO$_3$)$_3$ trilayers.

cond-mat.str-el↗