MS-E536, NHMFL, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA.
Wuhan National High Magnetic Field Center, School of Physics, Huazhong University of Science and Technology, 1037 Luoyu Road, 430074, Wuhan, China.
Sci Rep. 2017 May 4;7(1):1733. doi: 10.1038/s41598-017-01693-5.
The excitonic insulator phase has long been predicted to form in proximity to a band gap opening in the underlying band structure. The character of the pairing is conjectured to crossover from weak (BCS-like) to strong coupling (BEC-like) as the underlying band structure is tuned from the metallic to the insulating side of the gap opening. Here we report the high-magnetic field phase diagram of graphite to exhibit just such a crossover. By way of comprehensive angle-resolved magnetoresistance measurements, we demonstrate that the underlying band gap opening occurs inside the magnetic field-induced phase, paving the way for a systematic study of the BCS-BEC-like crossover by means of conventional condensed matter probes.
激子绝缘相长期以来一直被预测会在底层能带结构的带隙打开附近形成。据推测，随着底层能带结构从金属侧调谐到带隙打开的绝缘侧，配对的性质会从弱（BCS 样）耦合转变为强耦合（BEC 样）。在这里，我们报告了石墨的高磁场相图，该图显示了这种转变。通过综合角分辨磁阻测量，我们证明了底层带隙的打开发生在磁场诱导的相中，为通过传统凝聚态探针对 BCS-BEC 样交叉进行系统研究铺平了道路。
