We note that the properties of skyrmions capture many features of the ground states of quantum dots in strong magnetic fields. Therefore, in the present work we choose skyrmions with high winding numbers as trial ground states. In our results, we find that the occurrence of skyrmions fits an instability criterion of maximum density droplet very well. Interesting spin structures are found and such structures are recently supported by electron spin resonance experiments. The addition spectrum is calculated and the transition found in recent experiments is attributable to anti-skyrmion to skyrmion transition. The implication of pair tunneling from our trial wave function is discussed. ͓S0163-1829͑99͒10947-0͔ PHYSICAL REVIEW B 15 DECEMBER 1999-I VOLUME 60, NUMBER 23 PRB 60

The coexistence of RVB, flux phase, and antiferromagnetic states for the t-J model is studied within the frame work of the mean-field theory by means of the slave-boson approach. Two simple relations among these three order parameters manifesting the cooperative behavior of these states are derived. A phase diagram separating the antiferromagnetic from the non-antiferromagnetic state is obtained. Comparison with available previous work shows that our result agrees reasonably well. @ 1997 Elsevier Science B.V.