Morritt Alexander L, Lopez Jordan R, Blundell Toby J, Canadell Enric, Akutsu Hiroki, Nakazawa Yasuhiro, Imajo Shusaku, Martin Lee
School of Science and Technology , Nottingham Trent University , Clifton Lane , Nottingham NG11 8NS , United Kingdom.
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) , Campus de la UAB, 08193 Bellaterra , Spain.
Inorg Chem. 2019 Aug 19;58(16):10656-10664. doi: 10.1021/acs.inorgchem.9b00292. Epub 2019 Aug 5.
The series of salts β''-(BEDT-TTF)[(HO)(NH)M(CO)]·18-crown-6 show ambient-pressure superconductivity when M = Cr, Rh. Evidence indicates that the previously reported Cr and Rh salts show a bulk Berezinski-Kosterlitz-Thouless superconducting transition. The isostructural ruthenium and iridium salts are reported here. The Ir salt represents the first radical-cation salt to contain a 5d tris(oxalato)metalate anion. The Ru and Ir salts do not show superconductivity but instead undergo a broad chemically induced metal to insulator transition at 155 K for ruthenium and at 100 K for iridium. The axes of the Ru and Ir salts are much shorter than those of the Rh and Cr salts. Thus, the more stable metallic state of the Cr and Rh salts is associated with the more strongly 2D electronic systems. The different low-temperature behavior of the Ru and Ir salts, which exhibit a smaller interlayer spacing, could originate from a structural change in the anionic layer which thus can be easily transmitted to the donor layers and generate a localized state. However, another possibility is that it originates from Berezinski-Kosterlitz-Thouless effects.
当M = Cr、Rh时，一系列盐β''-(BEDT-TTF)[(HO)(NH)M(CO)]·18-冠-6呈现常压超导性。有证据表明，先前报道的Cr盐和Rh盐呈现体相 Berezinski-Kosterlitz-Thouless超导转变。本文报道了同构的钌盐和铱盐。铱盐是首个含有5d三(草酸根)金属酸根阴离子的自由基阳离子盐。钌盐和铱盐不呈现超导性，而是分别在155 K（钌盐）和100 K（铱盐）经历一个宽的化学诱导金属-绝缘体转变。钌盐和铱盐的 轴比铑盐和铬盐的短得多。因此，铬盐和铑盐更稳定的金属态与更强的二维电子系统相关。钌盐和铱盐具有较小的层间距，其不同的低温行为可能源于阴离子层的结构变化，这种变化可以很容易地传递到给体层并产生局域态。然而，另一种可能性是它源于Berezinski-Kosterlitz-Thouless效应。
