Universal Behavior of Two-DimensionalHe3at Low Temperatures

Abstract

On the example of two-dimensional (2D) 3 He we demonstrate that the main universal features of its experimental temperature T -density x phase diagram [see M. Neumann, J. Nyéki, J. Saunders, Science 317, 1356Science 317, (2007] look like those in the heavy-fermion metals. Our comprehensive theoretical analysis of experimental situation in 2D 3 He allows us to propose a simple expression for effective mass M * (T, x), describing all diverse experimental facts in 2D 3 He in unified manner and demonstrating that the universal behavior of M * (T, x) coincides with that observed in HF metals.PACS numbers: 72.15. Qm, 71.27.+a, 74.20.Fg, 74.25.Jb One of the main purposes of condensed matter physics is to unveil the nature of the non-Fermi liquid (NFL) behavior in various strongly correlated Fermi-systems. These substances, such as high temperature superconductors, heavy fermion (HF) metals, 2D electron and 3 He systems are the objects of intensive studies leading to understanding of many-body effects and quantum phase transitions responsible for the NFL behavior. Heavy fermion metals provide important examples of strongly correlated Fermi-systems [1,2]. In these compounds, being f-electron alloys, a lattice of f-electron spins couples to the itinerant electronic system by s − f Kondo exchange interaction. The properties of such systems are now hotly debated as there is a common wisdom that they are related to zero temperature quantum fluctuations, suppressing quasiparticles and giving rise to a quantum critical point (QCP), where the systems transit to different magnetic ground states generating their specific NFL behavior [2,3]. On the other hand, it was shown that the electronic system of HF metals demonstrates the universal low-temperature behavior irrespectively of their magnetic ground state [4]. Therefore it is of crucial importance to check whether this behavior can be observed in 2D Fermi systems. Fortunately, the recent measurements on 2D 3 He become available [5,6]. Their results are extremely significant as they allow to check the presence of the universal behavior in the system formed by 3 He atoms which are essentially different from electrons. Namely, the neutral atoms of 2D 3 He are fermions with spin S = 1/2 and they interact with each other by van-der-Waals forces with strong hardcore repulsion (due to electrostatic repulsion of protons) and a weakly attractive tail. The different character of interparticle interaction along with the fact, that a mass of He atom is 3 orders of magnitude larger then that of an electron, makes 3 He to have drastically different microscopic properties then that of 3D HF metals. Because of this difference nobody can be sure that the macroscopic physical properties of both above fermionic systems will be more or less similar to each other.The bulk liquid 3 He is historically the first object, to which a Landau Fermi-liquid (LFL) theory had been applied [7]. This substance, being intrinsically isotropic Fermi-liquid with negligible spin-orbit interaction is an ideal obj...

Anomalous magnetotransport in the heavy-fermion superconductor Ce2PdIn8

“…Interestingly, it seems that such a temperature dependence of R H indeed occurs below T min ≃ T NFL in weak magnetic field limit (see dashdotted line in Fig.1a). Recently, an approach called fermion condensation quantum phase transitions theory (FCQPT) has been derived for NFL systems, which explicitly takes into account m * dependencies on temperature, magnetic field and/or charge carrier density [22]. It seems tempting to numerically apply the FCQPT model to the magnetotransport data of Ce 2 PdIn 8 .…”

Quantum Criticality of Spin Liquids in Novel Insulators and Magnets

“…The presence of the residual value is clearly resolved in EtMe 3 Sb[Pd(dmit) 2 ] 2 , while measurements of κ/T on κ − (BEDT − TTF) 2 Cu 2 (CN) 3 suggest that the low-energy excitation spectrum can have a gap [45,46]. Taking into account the observed T -linear term of the heat capacity in κ − (BEDT − TTF) 2 Cu 2 (CN) 3 with the static spin susceptibility remaining finite down to the lowest measured temperatures [47], the presence of a gap in the spin excitation becomes questionable. Thermal conductivity probe elementary itinerant excitations and is totally insensitive to localized ones, such as those responsible for Schottky contributions, which contaminates the heat capacity measurements at low temperatures [42][43][44][45][46].…”

“…The scaling behavior of the thermodynamic properties coincides with that observed in HF metals and 2D 3 He. Herbertsmithite ZnCu 3 (OH) 6 Cl 2 exhibits the LFL, NFL and the transition behavior as HF metals and 2D 3 He do, see Sects. 6.3.1 and 18.4.…”

“…17.9 and 17.16. 3 have two-dimensional triangular lattices with the geometric frustration that prohibits spin ordering even at the lowest accessible temperatures T [42][43][44][45][46]. Therefore, being different form ZnCu 3 (OH) 6 Cl 2 , these insulators offer unique insights into the physics of quantum spin liquids (QSL).…”

“…Representing a special case of QSL, SCQSL is a quantum state of matter composed of spinons-chargeless fermionic particles with spin 1/2 [12,13,35]. In insulating compounds such as the organic insulators EtMe 3 Sb[Pd(dmit) 2 ] 2 and κ − (BEDT − TTF) 2 Cu 2 (CN) 3 , SCQSL can emerge when interactions among the magnetic components are incompatible with the underlying crystal geometry, leading to a geometric frustration generated by the triangular and kagome lattices of magnetic moments, as it is in the case of ZnCu 3 (OH) 6 Cl 2 , see e.g., [48,49]. In case of ideal 2D lattice, its frustration leads to a dispersionless topologically protected branch of the spectrum with zero excitation energy known as the flat band [24,25,50].…”