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arXiv · 2107.00130

Thermodynamic and transport properties of semiconducting two-dimensional metal-organic kagom\'e lattices with disorder

Tanya Berry·Jennifer R. Morey·Kathryn E. Arpino·Jin-Hu Dou·Claudia Felser·Mircea Dincă·Tyrel M. McQueen
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Abstract

The kagom\'e lattice is a fruitful source of novel physical states of matter, including the quantum spin liquid and Dirac fermions. Here we report a structural, thermodynamic, and transport study of the two-dimensional kagom\'e metal-organic frameworks Ni_3(HIB)v2 and Cu_3(HIB)_2 (HIB = hexaiminobenzene). Magnetization measurements yield Curie constants of 1.12 and 0.352 emu K mol f.u.-1 Oe-1 respectively, close to the values expected for ideal S=1 and S=1/2 moments. Weiss temperatures of -20.3 K and -6.52 K, respectively, indicate moderate to weak magnetic interactions. Electrical transport measurements reveal that both materials are semiconducting, with gaps of Eg = 22.2 and 103 meV, respectively. Specific heat measurements reveal a large T-linear contribution of {\gamma} = 148(4) mJ mol-f.u.-1 K-2 in Ni_3(HIB)_2 with only a gradual upturn below T ~ 5 K and no evidence of a phase transition to an ordered state down to T = 0.1 K. Cu_3(HIB)_2 also lacks evidence of a phase transition above T = 0.1 K, with a substantial, field-dependent, magnetic contribution below T ~ 5 K. Despite being superficially in agreement with expectations of magnetic frustration and spin liquid physics, we are able to explain these observations as arising due to known stacking disorder in these materials. Our results further state the art of kagom\'e lattice physics, especially in the rarely explored regime of semiconducting but not metallic behavior.

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Tanya Berry, Jennifer R. Morey, Kathryn E. Arpino, Jin-Hu Dou, Claudia Felser, Mircea Dincă, Tyrel M. McQueen. 2021-06-30. Thermodynamic and transport properties of semiconducting two-dimensional metal-organic kagom\'e lattices with disorder. https://arxiv.org/abs/2107.00130

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