When using Surface elevation, the elevation shadow effect below me will not be displayed

Question

val pagerState = rememberPagerState()
    Column {
        Surface(elevation = 2.dp) {
            Column() {
                SearchView()
                FixedTabLayout(data = tabs, pagerState = pagerState)
            }
        }
        CommonSpacer(5)//convenient testing
        ...
    }

private fun SearchView() {
    Row(
        modifier = Modifier
            .fillMaxWidth()
            .padding(horizontal = 16.dp)
            .padding(top = 8.dp, bottom = 8.dp)
            .height(32.dp)
            .background(colorResource(id = R.color.bgColorThird), RoundedCornerShape(32.dp)),
    ) {
        ...
    }
}
@Composable
fun FixedTabLayout(pagerState: PagerState, data: List<String>) {
    val coroutineScope = rememberCoroutineScope()
    TabRow(
        selectedTabIndex = pagerState.currentPage,
        modifier = Modifier
            .fillMaxWidth()
            .height(42.dp),
        backgroundColor = colorResource(id = R.color.white),
        divider = {}
    ) {
        ...
    }

}

I want to know why my Surface elevation setting does not work at this location. What I expect is that the searchView is above the tabLayout, and they are all at the top of the screen. The bottom of the tabLayout displays a 2dp shadow, just like covering the top of the screen。The picture below shows my current appearance and my expected appearance