TOKYO :Japan's Nikkei share average surged past the key 51,000 level for the first time on Wednesday, underpinned by investor optimism over artificial intelligence sector investments. The tech-heavy Nikkei 225 Index was up 2.05 per cent at an unprecedented 51,249.82, as of the midday break. The index crossed the key psychological barrier of 50,000 on Monday. The broader Topix index edged up less than 0.1 per cent, as a stronger yen weighed on most non-tech shares. Advantest, a key chip-testing