After lots of search finally this worked for me . I hope it helps.
public ActionResult LogOff()
{
AuthenticationManager.SignOut();
HttpContext.User = new GenericPrincipal(new GenericIdentity(string.Empty), null);
return RedirectToAction("Index", "Home");
}
<li class="page-scroll">@Html.ActionLink("Log off", "LogOff", "Account")</li>