/* Style Definitions */ table.MsoNormalTable {mso-style-name:”Table Normal”; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:””; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:”Times New Roman”,”serif”;} Transition metal dichalcogenides (TMD) were in fact the first genuine quasi two dimensional compounds where the CDW instability was found.  In this case, e.g. 1T-TaS2, the antiferromagnetic insulating phase of the undoped cuprates would correspond to the Mott localised fully commensurate CDW phase. With doping or application of pressure, domains of commensurate CDW are separated by interdomain phase which could be considered as stripes. With continued doping and pressure an unconventional metallic phase and superconductivity appear. We are exploring  finely traced parallels between TMD, organic ET superconductors, and cuprates

Phase Diagramme of transition metal dicalcogenides 1T-TaS2. The melting of the Mott-phase is followed by superconductivity.


Artistic view of the 2D planes decorated with CDWs in form of David stars.

Another original dichalcogenide system, subject of our investigations is Co0.33NbS2. Within the NbS2, layers intercalated Co forms a triangular lattice with an antiferromagnetic (AFM) order. The magnetism strongly influences the 2D elctronic transport. The application suppresses the AFM order and drives the system through the Doniach phase diagram, from the RKKY to Kondo  dominated interactions.

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[2] A. F. Kusmartseva, B. Sipos, H. Berger, L. Forró , and E. Tutiš, Pressure induced superconductivity in pristine 1T-TiSe2, Physical Review Letters 103, 236401 (2009).
[3] B. Sipos, A. F. Kusmartseva, A. Akrap, H. Berger, L. Forró & E. Tutiš, From Mott state to superconductivity in 1T-TaS2, Nature Materials 7, 960 – 965 (2008).