Gapless Excitations in the Ground State of 1T-TaS2


  Amit Ribak [1]  ,  Itai Silber [2]  ,  Christopher Baines [3]  ,  Khanan Chashka [1]  ,  Zaher Salman [3]  ,  Yoram Dagan [2]  ,  Amit kanigel [1]  
[1] Physics Department, Technion - Israel Institute of Technology
[2] Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University
[3] Paul Scherrer Institute, CH 5232 Villigen PSI, Switzerland

1T-TaS2 is a layered transition metal dichalcogenide with a very rich phase diagram. At T=180K it undergoes a metal to Mott insulator transition. Mott insulators usually display anti-ferromagnetic ordering in the insulating phase but 1T-TaS2 was never shown to order magnetically. We have shown that 1T-TaS2 has a large paramagnetic contribution to the magnetic susceptibility but it does not show any sign of magnetic ordering or freezing down to 20mK, as probed by µSR, possibly indicating a quantum spin liquid ground state. Although 1T-TaS2 exhibits a strong resistive behavior both in and out-of plane at low temperatures we find a linear term in the heat capacity suggesting the existence of a Fermi-surface, which has an anomalously strong magnetic field dependence.