Most popular post for last 7 days

I need to change the most popular post widgets with date restrictions.

For an example, how should I get most popular posts(post_views_count) of last 7 days.

original query,

$popularposts = new WP_Query('showposts=10meta_key=post_views_countorderby=meta_value_numorder=DESCignore_sticky_posts=1')

then I changed that to,

$args = array(
    'date_query' = array( array( 'after' = '-7 days' ) ),  
    'showposts' = 10,
    'ignore_sticky_posts' = 1,
    'meta_key' = 'post_views_count',
    'orderby' = 'meta_value_num',
    'order' = 'DESC'
);
$the_query = new WP_Query( $args );

However it doesn't give any results. How should I achieve this?

Thanks in advance.