D. Tsuji

NMR Measurements on New Quantum Phases in 2D 3He

Monolayer 3He is an ideal experimental system for studying strongly correlated two dimensional fermions. We measured magnetic properties of the second layer of 3He adsorbed on 4He‐preplated graphite by NMR in a wide temperature (70 μK. < T < 300 mK) and density (4.9 < p <9.8 nm−2) ranges. The measured magnetization isotherms can be classified into four distinct regions depending on density. The present NMR results support the scenario given by the recent heat capacity measurements that the region just below the density for the 4/7 commensurate phase is a hole‐doped Mott localized phase.

NMR Measurements of 2D 3He Adsorbed on ZYX Exfoliated Graphite

We describe first successful usage of ZYX exfoliated graphite to cool adsorbed two dimensional (2D) 3He to ugtra low temperatures (ULT). ZYX has much better characteristics as an adsorption substrate such as larger crystallite (platelet) size and smaller mosaic angle than Grafoil, a widely used exfoliated graphite in ULT experiments. In spite of the relatively small surface area of ZYX, we could perform a nuclear magnetization measurement of paramagnetic 2D solid 3He with continuous wave NMR below 10 mK. The data follow nicely the Curie law down to 200 µK. This indicates that ZYX can be used in experiments to study detailed density dependences of low temperature properties of 2D 3He including possible BCS transitions. We also show a preliminary resugt of pulsed NMR measurements of high density 2D fluid 3He adsorbed on ZYX preplated with a 4He monolayer.

Large mass enhancement in 3He monolayer fluids adsorbed on graphite preplated with 4He

A fluid monolayer of 3He adsorbed on a graphite surface is an ideal twodimensional (2D) Fermi system. We have observed very large mass enhancement of the quasiparticles (m*/m=20±5) in preliminary heat-capacity measurements for high density 3He fluids adsorbed on graphite preplated with a 4He monolayer (3He/4He/gr). This could be divergence of m* toward the critical density for the 4/7 phase with a triangular lattice, which is a registered phase commensurate against the first layer. The observed m* is larger than those reported for other 2D 3He systems, e.g., m*/m=13 for 3He/HD/HD/gr system, presumably because of the higher critical density. The apparent divergence of m* toward the different Critical densities strongly suggests the Mott–Hubbard type transition between the 2D Fermi fluid phase and the registered phase under a strong onsite hard core repulsion between the 3He atoms.