arXiv subjects

Carl Jonas Linnemann

Publications and source records attributed to Carl Jonas Linnemann.

3 recordsLinked to original sources

arXiv2026

Flat band in the multibandmetal MnSb$_2$

We report the realization of a metallic flat band in the marcasite compound MnSb$_2$. The material was synthesized under high pressure, and its crystal structure was established by X-ray diffraction. Electrical and thermoelectric transport measurements reveal signatures of a flat band near the Fermi level that persist across three structural, magnetic, and electronic transitions. These observations are supported by extensive density-functional-theory calculations. Related marcasite diantimonides, including FeSb$_2$ and CrSb$_2$, also host flat bands, but these lie far from the Fermi level and therefore do not produce a metallic flat-band state. MnSb$_2$ therefore emerges as the only known metallic marcasite antimonide in which a flat band lies in the vicinity of the Fermi level.

cond-mat.str-el↗

arXiv2026

High-pressure phase transitions in the quantum spin liquid candidate Na2Co2TeO6 probed by Raman spectroscopy

The quasi-2D magnet Na2Co2TeO6 (NCTO) is a candidate for a Kitaev Quantum Spin Liquid (KQSL) state. Pressure-tuning in such materials is of interest as a potential method to tune the Kitaev exchange interactions, which are strongly dependent on bond geometry. Here we report a Raman spectroscopic study of NCTO inside a diamond anvil cell (DAC) with pressure applied up to 16.3 GPa. Based on the changes in the Raman modes, this pressure range is divided into three regions. The appearance and disappearance of several modes and changes in the polarization dependence of the representative modes, most prominently above 13.8 GPa, point to pressure-induced phase transitions in this material.

cond-mat.str-el↗

arXiv2024

Weyl Semimetallic Phase in High Pressure CrSb$_2$ and Structural Compression Studies of its High Pressure Polymorphs

In this study, high pressure synchrotron powder X-ray diffraction is used to investigate the compression of two high pressure polymorphs of \ce{CrSb2}. The first is the \ce{CuAl2}-type polymorph with an eight-fold coordinated Cr, which can be quenched to ambient conditions from high-pressure high-temperature conditions. The second is the recently discovered \ce{MoP2}-type polymorph, which is induced by compression at room temperature, with a seven-fold coordinated Cr. Here, the assigned structure is unambiguously confirmed by solving it from single-crystal X-ray diffraction. Furthermore, the electrical properties of the \ce{MoP2}-type polymorph were investigated theoretically and the resistance calculations under pressure were accompanied by resistance measurements under high pressure on a single crystal of \ce{CrSb2}. The calculated electronic band structure for the \ce{MoP2}-type phase is discussed and we show that the polymorph is semimetallic and possesses type-I Weyl points. No further phase transitions were observed for the \ce{CuAl2}-type structure up to 50 GPa and 40 GPa for the \ce{MoP2}-type structure. Even though the \ce{CuAl2}-phase has the highest coordination number of Cr, it was found to be less compressible than the \ce{MoP2}-phase having a seven-fold coordinated Cr, which was attributed to the longer Cr-Sb distance in the \ce{CuAl2}-type phase. The discovery of a type-I Weyl semimetallic phase in \ce{CrSb2} opens up for discovering other Weyl semimetals in the transition metal di-pnictides under high pressure.

cond-mat.mtrl-sci↗