Unconventional superconductivity from lattice quantum disorder

摘要

该研究采用第一性原理路径积分分子动力学方法，全面纳入原子核量子多体效应，构建自由能面，在H₃S和La₃Ni₂O₇中发现了晶格量子无序（LQD）相。通过对比经典与量子相边界，LQD相在压力-温度相图中形成一个三角形区域，其左边界与超导穹顶左侧翼的转变温度精确对齐，且LQD相的最高温度Tcmax与超导T_c最大值重合，同位素效应亦被准确捕捉。这揭示穹顶左翼超导起源于低对称相向量子无序相的转变，超导态完全位于高对称相，从而推翻双相解释。研究确立了LQD相作为统一框架，不仅阐明了非常规超导电性中晶格量子多体效应的关键作用，还为预测更高T_c超导体及解释凝聚态反常现象开辟了新途径。

材料

• H₃S
• La₃Ni₂O₇
• D₃S

方法

• path-integral molecular dynamics (PIMD)
• DFT
• machine learning inter-atomic potentials
• centroid potential of mean force
• conventional molecular dynamics (MD)

关键词

• lattice quantum disorder
• nuclear quantum many body effects
• quantum order disorder transition
• superconducting dome
• unconventional superconductivity
• pressure temperature phase diagram
• isotope effect

亮点

• First rigorous description of a lattice quantum disordered phase in real materials using first-principles path-integral molecular dynamics.
• The precise alignment between the left LQD boundary and the superconducting dome's left flank reveals the origin of superconductivity on the left flank.
• The maximum temperature of the LQD phase exactly matches the maximum superconducting T_c for both H₃S and La₃Ni₂O₇.
• The LQD phase transcends the conventional phonon picture and may host a novel pairing mechanism.
• This framework provides a practical route for predicting higher-T_c superconductors by identifying materials with a large LQD phase.

结论

• A lattice quantum disordered (LQD) phase is discovered in H₃S and La₃Ni₂O₇ via first-principles PIMD.
• The left boundary of the LQD phase precisely aligns with the left flank of the superconducting dome.
• The maximum temperature of the LQD phase coincides with the maximum superconducting transition temperature T_c.
• Superconductivity on the left flank originates from a transition from a low-symmetry phase to the LQD phase and resides entirely in the high-symmetry phase, refuting two-phase interpretations.
• The LQD phase is a key ingredient of the pairing mechanism and establishes lattice quantum disorder as a unifying framework for unconventional superconductivity.

主要论断

• The left flank of the superconducting dome in H₃S and La₃Ni₂O₇ originates from the structural transition into the lattice quantum disordered phase.
  • 证据: Left boundary of LQD phase coincides with T_c values on the dome’s left flank.,Isotope effect in superconductivity accurately captured by LQD phase boundaries.
• The maximum temperature of the LQD phase coincides with the maximum superconducting T_c, establishing the LQD phase as a decisive factor in the pairing mechanism.
  • 证据: T_max(LQD) = 220 K (H₃S), 160 K (D₃S), 77 K (La₃Ni₂O₇) match experimental peak T_c.,Agreement robust across different exchange-correlation functionals.

研究流程

• sample_preparation — Computational models of superconducting materials established for quantum and classical simulations.
  • 材料: H₃S; La₃Ni₂O₇
  • 方法: first-principles DFT calculations with PBE functional; machine learning inter-atomic potentials generation
  • 观察: potential energy surfaces using the computational models prepared for PIMD and MD simulations
• measurement — Nuclear quantum many-body effects and thermal fluctuations included; structural phase boundaries identified via spectral and structural data.
  • 材料: H₃S; La₃Ni₂O₇
  • 方法: path-integral molecular dynamics (PIMD); classical molecular dynamics (MD)
  • 观察: lattice dispersion from centroid effective forces; soft-mode frequency at Γ point across P and T; pair distribution function from MD
• analysis — Lattice quantum disordered phase defined; its left boundary aligns with experimental T_c on the left flank of the superconducting dome.
  • 方法: centroid potential of mean force from PIMD to construct free energy surface; curvature analysis to locate phase boundaries; comparison of quantum (PIMD) and classical (MD) boundaries
  • 观察: quantum phase boundary shifting to higher pressure with T; classical phase boundary; triangular LQD region; T_max(LQD) values: 220 K for H₃S, 160 K for D₃S, 77 K for La₃Ni₂O₇
• interpretation — Superconductivity on the dome’s left flank originates from the transition into the LQD phase; the superconducting state resides entirely within the high-symmetry phase; LQD phase is a key pairing mechanism ingredient.
  • 材料: H₃S; La₃Ni₂O₇
  • 方法: direct comparison with published experimental T_c data; isotope effect validation (H₃S vs D₃S)
  • 观察: left LQD boundary precisely tracks the left flank T_c; T_max(LQD) matches peak T_c (220 K, 80 K); isotope effect captured