skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Thermodynamic properties and enhancement of diamagnetism in nitrogen doped lutetium hydride synthesized at high pressure
Title: Thermodynamic properties and enhancement of diamagnetism in nitrogen doped lutetium hydride synthesized at high pressure
Nitrogen doped lutetium hydride has drawn global attention in the pursuit of room-temperature superconductivity near ambient pressure and temperature. However, variable synthesis techniques and uncertainty surrounding nitrogen concentration have contributed to extensive debate within the scientific community about this material and its properties. We used a solid-state approach to synthesize nitrogen doped lutetium hydride at high pressure and temperature (HPT) and analyzed the residual starting materials to determine its nitrogen content. High temperature oxide melt solution calorimetry determined the formation enthalpy of LuH1.96N0.02(LHN) from LuH2and LuN to be −28.4 ± 11.4 kJ/mol. Magnetic measurements indicated diamagnetism which increased with nitrogen content. Ambient pressure conductivity measurements observed metallic behavior from 5 to 350 K, and the constant and parabolic magnetoresistance changed with increasing temperature. High pressure conductivity measurements revealed that LHN does not exhibit superconductivity up to 26.6 GPa. We compressed LHN in a diamond anvil cell to 13.7 GPa and measured the Raman signal at each step, with no evidence of any phase transition. Despite the absence of superconductivity, a color change from blue to purple to red was observed with increasing pressure. Thus, our findings confirm the thermodynamic stability of LHN, do not support superconductivity, and provide insights into the origins of its diamagnetism.  more » « less
Award ID(s):
2052527 2111812
PAR ID:
10496461
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
Proceedings of the National Academy of Sciences of the United States of America
Date Published:
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
121
Issue:
12
ISSN:
0027-8424
Page Range / eLocation ID:
e2321540121
Subject(s) / Keyword(s):
Material synthesis and characterization. Superconductivity
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Nature communications)
    - (Ed.)
    High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB2 during compression induces superconductivity above 50 GPa with a maximum super-conducting critical temperature, Tc of 17 K at 91 GPa. Upon further compression up to 187 GPa, the Tc gradually decreases. Theoretical calculations show that electron-phonon mediated super-conductivity originates from the formation of metastable stacking faults and twin boundaries that exhibit a local structure resembling MgB2 (hP3, space group 191, prototype AlB2). Synchrotron x-ray diffraction measurements up to 145 GPa show that the ambient pressure hP12 structure (space group 194, prototype WB2) continues to persist to this pressure, consistent with the formation of the planar defects above 50 GPa. The abrupt appearance of superconductivity under pressure does not coincide with a structural transition but instead with the formation and percolation of mechanically-induced stacking faults and twin boundaries. The results identify an alternate route for designing superconducting materials. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Proceedings of the National Academy of Sciences)
    In light of breakthroughs in superconductivity under high pressure, and considering that record critical temperatures (Tcs) across various systems have been achieved under high pressure, the primary challenge for higher Tcshould no longer solely be to increase Tcunder extreme conditions but also to reduce, or ideally eliminate, the need for applied pressure in retaining pressure-induced or -enhanced superconductivity. The topological semiconductor Bi0.5Sb1.5Te3(BST) was chosen to demonstrate our approach to addressing this challenge and exploring its intriguing physics. Under pressures up to ~50 GPa, three superconducting phases (BST-I, -II, and -III) were observed. A superconducting phase in BST-I appears at ~4 GPa, without a structural transition, suggesting the possible topological nature of this phase. Using the pressure-quench protocol (PQP) recently developed by us, we successfully retained this pressure-induced phase at ambient pressure and revealed the bulk nature of the state. Significantly, this demonstrates recovery of a pressure-quenched sample from a diamond anvil cell at room temperature with the pressure-induced phase retained at ambient pressure. Other superconducting phases were retained in BST-II and -III at ambient pressure and subjected to thermal and temporal stability testing. Superconductivity was also found in BST with Tcup to 10.2 K, the record for this compound series. While PQP maintains superconducting phases in BST at ambient pressure, both depressurization and PQP enhance its Tc, possibly due to microstructures formed during these processes, offering an added avenue to raise Tc. These findings are supported by our density-functional theory calculations. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Materials Today Physics)
    - (Ed.)
    High-pressure studies on elements play an essential role in superconductivity research, with implications for both fundamental science and applications. Here we report the experimental discovery of surprisingly low pressure driving a novel germanium allotrope into a superconducting state in comparison to that for α-Ge. Raman measurements revealed structural phase transitions and possible electronic topological transitions under pressure up to 58 GPa. Based on pressure-dependent resistivity measurements, superconductivity was induced above 2 GPa and the maximum Tc of 6.8 K was observed under 4.6 GPa. Interestingly, a superconductivity enhancement was discovered during decompression, indicating the possibility of maintaining pressure-induced superconductivity at ambient pressure with better superconducting performance. Density functional theory analysis further suggested that the electronic structure of Ge (oP32) is sensitive to its detailed geometry and revealed that disorder in the β-tin structure leads to a higher Tc in comparison to the perfect β-tin Ge. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB 2 during compression induces superconductivity above 50 GPa with a maximum superconducting critical temperature, T c of 17 K at 91 GPa. Upon further compression up to 187 GPa, the T c gradually decreases. Theoretical calculations show that electron-phonon mediated superconductivity originates from the formation of metastable stacking faults and twin boundaries that exhibit a local structure resembling MgB 2 (hP3, space group 191, prototype AlB 2 ). Synchrotron x-ray diffraction measurements up to 145 GPa show that the ambient pressure hP12 structure (space group 194, prototype WB 2 ) continues to persist to this pressure, consistent with the formation of the planar defects above 50 GPa. The abrupt appearance of superconductivity under pressure does not coincide with a structural transition but instead with the formation and percolation of mechanically-induced stacking faults and twin boundaries. The results identify an alternate route for designing superconducting materials. 
    more » « less
  5. ; ; ; ; ; ; ; (, Advanced Functional Materials)
    Abstract The current pressing challenge in the field of superconducting hydride research is to lower the stable pressure of such materials for practical applications. Molecular hydrides are usually stable under moderate pressure, but the underlying metallization mechanism remains elusive. Here, the important role of chemical interactions in governing the structures and properties of molecular hydrides is demonstrated. A new mechanism is proposed for obtaining high‐temperature and even room‐temperature superconductivity in molecular hydrides and report that the ternary hydride NaKH12hostsTcvalues up to 245 K at moderate pressure of 60 GPa. Both the excellent stability and superconductivity of NaKH12originate from the fact that the localized electrons in the interstitial region of the metal lattice occupying the crystal orbitals well matched with the hydrogen lattice and forming chemical templates to assist the assembly of H2units. These localized electrons weaken the H─H covalent bonds and improve the charge connectivity between the H2units, ensuring the strong coupling between electrons and hydrogen‐dominated optical phonons. The theory provides a key perspective for understanding the superconductivity of molecular hydrides with various structural motifs, opening the door to obtaining high‐temperature superconductors from molecular hydrides at moderate pressures. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email