????:1???????:??????

2?????v

3?????vx

4?????????

5????????

??????12??12?????? (?????????????? ???????????????)??????12???????????????????,??????????????????????«??»(Physical Review Letters)?

???,???????????????????????????????????????????????????,???,???????????????????????

????????,?????,???????????????????????????????,????????????????????

???????????,?????????????????????????????,????????????,?????,??????????????8??9?????????????????????????,?5???(??) ???????????????????:????????????????