After logout on SSO still access_token is being valid

I have an SPA angular using @okta/okta-angular package and backend i am using .Net Core. If i duplicate same application to the multiple tabs. One tab application logged out, i am working in other tab application its working fine. The access_token is taking as valid. I am thinking If one application logged out other application access_token should be invalid in same browser. But its allowing access_token be valid. Please explain me how it is working. This is the below .net core code we are using to validate.

services.AddAuthentication(options =>
options.DefaultAuthenticateScheme = OktaDefaults.ApiAuthenticationScheme;
options.DefaultChallengeScheme = OktaDefaults.ApiAuthenticationScheme;
options.DefaultSignInScheme = OktaDefaults.ApiAuthenticationScheme;
.AddOktaWebApi(new OktaWebApiOptions()
OktaDomain = appSettings.Settings.OktaDomain

Validating token using ClaimsIdentity

if (context.HttpContext != null)
var principal = context.HttpContext.User.Identity as ClaimsIdentity;
UserName = principal.Claims
.SingleOrDefault(c => c.Type == ClaimTypes.NameIdentifier)
OktaUserId = principal.Claims
.SingleOrDefault(c => c.Type == Constants.Constants.Uid)

            var tokenService = new TokenValidatorService(appSettings);
            if (UserName != null)
                var valid = tokenService.ValidateUser(UserName);
                UserId = valid.Result.UserId;