据悉，莫特金属-绝缘体转变是凝聚态物理学中最基本的现象之一。然而，经典的Brinkman-Rice莫特局域化图的基本原理仍然需要通过直接探测准粒子费米表面和有效质量的量子振荡测量进行实验测试。
通过将该技术扩展到高压，研究人员在清洁的、未掺杂的NiS2晶体中检测到了莫特局域化阈值上的金属态。研究发现：i)在接近莫特局域化时，准粒子质量显著增强，而费米表面基本保持不变; ii)准粒子质量密切遵循理论预测的发散形式，确立了载流子减速作为金属-绝缘体转变的驱动因素; iii)这种质量发散被金属-绝缘体转变截断，将莫特临界点置于相图的绝缘部分内。NiS2中莫特临界点的不可及性与清洁金属系统中铁磁性阈值的发现相似，在清洁金属系统中，低温临界几乎普遍被一阶相变或新的涌现相(如不相称的磁序或非常规的超导性)所中断。
附：英文原文
Title: Truncated mass divergence in a Mott metal
Author: Semeniuk, Konstantin, Chang, Hui, Baglo, Jordan, Friedemann, Sven, Tozer, Stanley W., Coniglio, William A., Gama, Monika B., Reiss, Pascal, Alireza, Patricia, Leermakers, Inge, McCollam, Alix, Grockowiak, Audrey D., Grosche, F. Malte
Issue&Volume: 2023-9-11
Abstract: The Mott metal–insulator transition represents one of the most fundamental phenomena in condensed matter physics. Yet, basic tenets of the canonical Brinkman-Rice picture of Mott localization remain to be tested experimentally by quantum oscillation measurements that directly probe the quasiparticle Fermi surface and effective mass. By extending this technique to high pressure, we have examined the metallic state on the threshold of Mott localization in clean, undoped crystals of NiS2. We find that i) on approaching Mott localization, the quasiparticle mass is strongly enhanced, whereas the Fermi surface remains essentially unchanged; ii) the quasiparticle mass closely follows the divergent form predicted theoretically, establishing charge carrier slowdown as the driver for the metal–insulator transition; iii) this mass divergence is truncated by the metal–insulator transition, placing the Mott critical point inside the insulating section of the phase diagram. The inaccessibility of the Mott critical point in NiS2 parallels findings at the threshold of ferromagnetism in clean metallic systems, in which criticality at low temperature is almost universally interrupted by first-order transitions or novel emergent phases such as incommensurate magnetic order or unconventional superconductivity.
DOI: 10.1073/pnas.2301456120
Source: https://www.pnas.org/doi/10.1073/pnas.2301456120