A high functioning team can’t be created by decree. Real teams — ones that do collective work — perform well not when the boss demands it, but when their colleagues expect it.
Your job as a team leader is not to direct the work of individual members, but to bring the group together around a common purpose and agreed upon goals. Then use the social bonds between members to influence their behavior. Encourage members to work hard not as a way to please you, but so that they don’t let everyone else down. If a team member fails to perform, don’t jump in right away. Let the other members correct him and give him feedback. This indirect approach is hard for some leaders, especially those who like direct control, but ultimately your people will perform better when they feel they’re part of a team.