Stability and Response of Vortex Solid Formed in Second Landau Level

Physical properties of the vortex solid phase formed in the second Landau level (2LL), which may be stabilized by strong paramagnetic pairbreaking (PPB), are examined in type II limit with no magnetic screening. First, it is shown that the spectrum of the low energy mode of this vortex solid has the same form as that of the conventional vortex solid in the first (i.e., the lowest) Landau level. Using this result, the melting line of the 2LL vortex solid is examined according to the Lindemann criterion. In contrast to the properties in equlibrium, the electromagnetic response of this vortex solid is quite unusual: Reflecting the presence of antivortices supporting the stability of the lattice structure, the superfluid stiffness measuring the response for a current perpendicular to the magnetic field is found to be nonvanishing, and its sign depends upon the applied current direction. Consequences of this response property are briefly discussed.