Momentum-Resolved Fingerprint of Mottness in Layer-Dimerized Nb$_3$Br$_8$
| Autor: | Date, Mihir, Petocchi, Francesco, Yen, Yun, Krieger, Jonas A., Pal, Banabir, Hasse, Vicky, McFarlane, Emily C., Körner, Chris, Yoon, Jiho, Watson, Matthew D., Strocov, Vladimir N., Xu, Yuanfeng, Kostanovski, Ilya, Ali, Mazhar N., Ju, Sailong, Plumb, Nicholas C., Sentef, Michael A., Woltersdorf, Georg, Schüler, Michael, Werner, Philipp, Felser, Claudia, Parkin, Stuart S. P., Schröter, Niels B. M. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | In a well-ordered crystalline solid, insulating behaviour can arise from two mechanisms: electrons can either scatter off a periodic potential, thus forming band gaps that can lead to a band insulator, or they localize due to strong interactions, resulting in a Mott insulator. For an even number of electrons per unit cell, either band- or Mott-insulators can theoretically occur. However, unambiguously identifying an unconventional Mott-insulator with an even number of electrons experimentally has remained a longstanding challenge due to the lack of a momentum-resolved fingerprint. This challenge has recently become pressing for the layer dimerized van der Waals compound Nb$_3$Br$_8$, which exhibits a puzzling magnetic field-free diode effect when used as a weak link in Josephson junctions, but has previously been considered to be a band-insulator. In this work, we present a unique momentum-resolved signature of a Mott-insulating phase in the spectral function of Nb$_3$Br$_8$: the top of the highest occupied band along the out-of-plane dimerization direction $k_z$ has a momentum space separation of $\Delta k_z=2\pi/d$, whereas the valence band maximum of a band insulator would be separated by less than $\Delta k_z=\pi/d$, where $d$ is the average spacing between the layers. As the strong electron correlations inherent in Mott insulators can lead to unconventional superconductivity, identifying Nb$_3$Br$_8$ as an unconventional Mott-insulator is crucial for understanding its apparent time-reversal symmetry breaking Josephson diode effect. Moreover, the momentum-resolved signature employed here could be used to detect quantum phase transition between band- and Mott-insulating phases in van der Waals heterostructures, where interlayer interactions and correlations can be easily tuned to drive such transition. Comment: 9 pages, 3 figures |
| Databáze: | arXiv |
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