【时   间】 22-Nov-2023  3pm

【地   点】 Room 320

【报告人】 Prof. Denis Arcon (Jozef Stefan Institute/University of Ljubljana, Slovenia)

【主持人】 Katsumi Tanigaki ( BAQIS）

【题   目】Antiferromagnetism and Superconductivity in Low-dimensional Systems

【摘   要】The competition between antiferromagnetism and superconductivity is one of the central questions in the research of strongly correlated systems. In this talk we will discuss their behaviour when low-dimensionality emphasises the importance of quantum fluctuations at low-temperatures.

In the first part of the talk, we will focus on quantum magnetism that has proven to be a very rich playground to uncover novel states of matter. In certain low-dimensional magnetic systems the role of geometrical frustration is typically manifested in a drastic suppression of Néel temperature, in a state with a very complicated non-collinear magnetic order or even in a complete suppression of long-range magnetic order and establishment of elusive quantum spin liquid. I will demonstrate the crucial role of geometrical frustration and reduced dimensionality on selected examples: the β-TeVO₄ compound comprising frustrated chains and the layered 1T-TaS₂ with a triangular lattice. I will also show that 1T-TaS₂ may not be an isolated case of frustrated antiferromagnetism among layered dichalcogenides.

Interactions in one dimension lead to a physics radically different from that in the higher dimensional counterparts. As opposed to excitations resembling individual particles (such as quasiparticle excitations), in one-dimension interactions will turn any excitation into a collective one. The physics of such one-dimensional solids can be well described by the universal concepts of Tomonaga-Luttinger liquids (TLL). Here we will focus on the superconducting properties of A₂Mo₃As₃ (A= alkali metal) characterized by one of the highest critical temperatures Tc ≈ 11 K among quasi-one-dimensional superconductors. 75As nuclear quadrupole relaxation rates, 1/T1, reveal that superconductivity develops directly from the TLL and is characterized by ~T5 suppression of 1/T1 below Tc. Moreover, muon spin relaxation (μSR) study shows a characteristic relaxation of μSR signal due to vortex lattice broadening and the modeling of the μSR relaxation reveals that the unconventional superconductivity is indeed a realistic possibility for A₂Mo₃As₃.

【报告人简介】Denis Arcon received his Bachelor of Science, Physics, Faculty of Mathematics and Physics, University of Ljubljana 1989-1993 and Doctor of Philosophy, Physics, Faculty of mathematics and physics, University of Ljubljana, Slovenia in 1997. He spent his Post-doctoral position at the University of Sussex, Brighton, UK from 1997-2000. He became Researcher at the Institute Jozef Stefan, Ljubljana in 2000, Slovenia, Assistant Professor at the Faculty of Mathematics and Physics, University of Ljubljana, Slovenia in 2001 and became the head of Pulsed EPR laboratory; Solid state physics department, Institute Jozef Stefan Institute. He became Professor of Josef Stefan Institute in 2009. He is presently the head of Department of Physics, Jozef Stephane Institute and also Professor at the Faculty of Mathematics and Physics, University of Ljubljana, Slovenia. He was awarded International Union for Materials Research (IUMRS) Award in 1999, Jozef Stefan Golden Emblem Prize in 2008, Ziga Zois Award in 2019 for his outstanding achievements in the fields of quantum magnetism and unusual superconductivity.