摘要
无限层镍酸盐超导体为研究奇异金属的量子临界起源提供了新平台，但其薄膜形式无法进行传统量热测量。本研究利用塞贝克系数作为低温比热的替代探针，在临界掺杂点x*处发现：高温区塞贝克响应与ARPES测得的能带结构定量吻合，表明存在明确定义的准粒子；而在60开尔文以下，S/T出现对数发散并持续到最低温（磁场抑制超导后），这标志着x*是一个终止欠掺杂相的量子临界点。此外，Ni-dx2-y2轨道的载流子密度从x*之上的1+x陡降至x*之下的x，重现了铜氧化物中赝能隙相的标志性特征。这些结果表明，无限层镍酸盐的欠掺杂区是一种类赝能隙态，其终结处涌现出T线性电阻率的奇异金属行为，从而为奇异金属的量子临界起源提供了有力证据。
材料
本批次暂无数据。
方法
本批次暂无数据。
关键词
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亮点
本批次暂无数据。
结论
本批次暂无数据。
主要论断
- At doping x*, the low-temperature Seebeck coefficient (S/T) exhibits a logarithmic divergence persisting after suppression of superconductivity, marking x* as a quantum critical point.
- 证据: Seebeck measurements show S/T ∝ log(T) below 60 K at x* (Fig. 2a),No divergence at neighboring dopings (x=0.06, 0.38),Superconductivity suppressed with B=41.5T
- Above 60 K, the high-temperature Seebeck response at x* is quantitatively reproduced by ARPES band structure calculations, indicating well-defined quasiparticles.
- 证据: Boltzmann transport calculation based on ARPES dispersion matches measured S magnitude and sign (Fig. 2b)
- The carrier density of the Ni-dx2-y2 band drops from 1+x to x across x*, analogous to the pseudogap carrier loss in cuprates.
- 证据: Two-band analysis of Hall coefficient data from Lee et al. (2023) shows abrupt drop at x*,Hall coefficient sign change from positive to negative
研究流程
- measurement
- 材料: La1-xSrxNiO2 thin films
- 方法: Seebeck coefficient measurements as function of temperature and doping; suppression of superconductivity using B=41.5 T magnetic field
- 观察: Above 60 K, S is constant and negative; below 60 K, S/T diverges logarithmically at x*; No logarithmic divergence at neighboring dopings (x=0.06, 0.38); Superconductivity suppressed to reveal normal-state divergence
- analysis
- 材料: ARPES band structure data from prior work; Hall coefficient data from Lee et al.
- 方法: Boltzmann transport calculation to compute S from ARPES dispersion; Two-band model fit to zero-temperature Hall coefficient to extract Ni-d carrier density
- 观察: Computed S matches measured S in sign and magnitude above 60K; Ni-d carrier density n_d drops from 1+x to x across x*
- interpretation — The doping x* is a quantum critical point terminating a pseudogap-like phase, from which strange metal behavior (T-linear resistivity) emerges; analogies with cuprates established.