よもぎ〜ぃぃ
D論いつくれるの?
くれるって言ってたじゃ〜ン
No purpose, No design...
"Correlation-Enhanced Effective Mass of Two-Dimensional Electrons in MgxZn1-xO/ZnO Heterostructures"http://prl.aps.org/abstract/PRL/v109/i24/e246401
Y. Kasahara et al.
Phys. Rev. Lett. 109, 246401 (2012)
We performed combined magnetotransport and cyclotron resonance experiments on two-dimensional electron systems confined in the MgxZn1-xO/ZnO heterostructures over a wide range of carrier densities, from 1.9 to 12×1011 cm-2 (3.5≲rs≲10, where rs is the Wigner-Seitz radius). As the carrier density was reduced, the transport mass mtr* was strongly enhanced. In marked contrast, the effective masses determined from the cyclotron resonance mCR* were found to be independent of the carrier density and as large as the bulk effective mass. The large enhancement of mtr*, which exceeds mCR* by ∼60%, at the lowest carrier density with rs∼10 is purely attributed to the strong electron correlation.
"Novel Pauli-paramagnetic quantum phase in a Mott insulator"
D. Watanabe et al.
Nature Commun. 3 (2012) 1090.
In Mott insulators, the strong electron–electron Coulomb repulsion localizes electrons. In dimensions greater than one, their spins are usually ordered antiferromagnetically at low temperatures. Geometrical frustrations can destroy this long-range order, leading to exotic quantum spin liquid states. However, their magnetic ground states have been a long-standing mystery. Here we show that a quantum spin liquid state in the organic Mott insulator EtMe3Sb[Pd(dmit)2]2 (where Et is C2H5−, Me is CH3−, and dmit is 1,3-dithiole-2-thione-4,5-dithiolate) with two-dimensional triangular lattice has Pauli-paramagnetic-like low-energy excitations, which are a hallmark of itinerant fermions. Our torque magnetometry down to low temperatures (30 mK) up to high fields (32 T) reveals distinct residual paramagnetic susceptibility comparable to that in a half-filled two-dimensional metal, demonstrating the magnetically gapless nature of the ground state. Moreover, our results are robust against deuteration, pointing toward the emergence of an extended 'quantum critical phase', in which low-energy spin excitations behave as in paramagnetic metals with Fermi surface, despite the frozen charge degree of freedom.
hugolab
hugo's blog:今週の傾向