Dresden 2020 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: Superconductivity: Sample Preparation, Characterization, Properties and Electronic Structure
TT 2.4: Talk
Monday, March 16, 2020, 10:15–10:30, HSZ 103
STM and STS studies of superconducting 1T-TaSeS — •Marion A. van Midden1, Yaroslav Gerasimenko1,2, Petra Šutar1, Erik Zupanič1, and Dragan Mihailovic1,2 — 1Jožef Stefan Institute, Ljubljana, Slovenia — 2Center of Excellence in Nanoscience and Nanotechnology, Ljubljana, Slovenia
In 1T-TaS2, similarly to many high-temperature superconductors, superconductivity, charge density waves (CDW) and Mott insulating (MI) states coexist. The MI state is suppressed upon doping [1], substitution [2] or pressure [3]. Until recently, it has been believed that this, together with the formation of CDW domain walls, is crucial for the onset of superconductivity. However, recent studies at T > TSC have challenged this hypothesis in 1T-TaS2 and 1T-TaSexS2−x [4].
We study superconducting 1T-TaSeS close to optimal TSC = 3.5 K using high-resolution scanning tunneling spectroscopy (STS) both below and above TSC. In contrast to pure 1T-TaS2 we observe a finite density of states inside the Mott gap both inside the domains and at the domain walls. STS at T = 1.2 K shows a small 1-2 meV gap at the Fermi level that vanishes at T > 5K, strongly suggesting it is related to SC. It is clearly uncorrelated with the CDW domain walls of any kind in clear contrast with the simple domain wall picture. This suggest a different, correlated picture of SC onset.
[1] L. J. Li et al., European Physics Letters 97, 67005 (2012).
[2] Y. Liu et al., Applie Physics Letters. 102, 192602 (2013).
[3] B. Sipos et al., Nature Materials 7, 960 (2008).
[4] J. Skolimowski, Y. Gerasimenko and R. Žitko, PRL, 122 (2019).